Rozprawy doktorskie na temat „Cognition in old age”

As humans age, the brain undergoes many changes. This includes loss of the neurotransmitter dopamine, which forms a bridging link between age and the ensuing changes in cognition. However many questions about the precise nature of this relationship with regards to brain structure and function remain unanswered. These questions are important given our expanding aging population, and the answers may help the discovery of new therapeutic interventions for age-related impairments as well as identify mechanisms to promote successful aging. Old age also provides a model for understanding the role of dopamine in many fundamental human behaviours. The aim of my research was to use a multimodal approach to explore the contribution of dopamine to learning and memory in healthy older age. In this thesis I present four studies in which I used a combination of behavioural testing, pharmacological manipulation, structural and functional magnetic resonance imaging in older adults. I show that dopamine boosts delayed episodic memory in a non-linear dose-dependent manner. Using functional MRI, I show this effect is mediated through consolidation rather than encoding by the hippocampus. In two further imaging studies conducted to explore the role of dopamine in reward-based learning, I show that the flexibility of learning depends on the structural integrity of the substantia nigra/ventral tegmental area (the origin of dopamine projections) and that pharmacological enhancement of dopamine levels can remediate abnormal reward processing in the ventral striatum. Individual differences in neural activity associated with reward prediction also relate to anatomical nigro-striatal connectivity, identified using diffusion tensor imaging. Finally, I show that in old age, valence influences decision-making in relation to ones own beliefs about the future, mediated by volume of the anterior cingulate cortex. I conclude this thesis with a brief discussion of the implications of these findings, study limitations and potential future studies.

This thesis contains two studies which examined the cognitive functioning of the aging brain. Specifically, age-related changes in processing speed and its remediation via cognitive training were studied. In study 1, younger adults (n = 34) and older adults (n = 39) were recruited to investigate the age-related differences in the relationships between processing speed and general cognitive status (GCS). Their performance in GCS (as measured by The Montreal Cognitive Assessment, Hong Kong Version), cognitive processing speed (as measured by Processing Speed Index, Wechsler Adult Intelligence Scale), cognitive inhibition (as measured by Stroop Color-Word Test), and divided attention (as measured by Color Trails Test) was examined. Current findings indicated that processing speed predicted GCS in older but not younger adults. In older adults, processing speed as a predictor accounted for an additional 13% of variance in GCS. This study further verified the relationship between processing speed and prefrontal abilities, including verbal fluency, cognitive inhibition and divided attention in aging. Findings revealed that despite the abovementioned prefrontal abilities were significantly correlated with processing speed, verbal fluency had remained the strongest predictor, accounting for 21% of variance in processing speed in older adults. Based on findings in study 1, it was anticipated that training cognitive skills including processing speed and prefrontal abilities in older adults would improve cognitive functioning in general. Therefore, in study 2, elderly people at risk of progressive cognitive decline (n = 70) were recruited to investigate the training effect of computerized cognitive training programs that aimed to improve cognitive processing speed, cognitive inhibition and divided attention. Findings indicated that cognitive processing speed and divided attention improved post-training. Results obtained from the two studies implied potential intervention through training cognitive processing speed in elderly people at risk of progressive cognitive decline. Future studies should focus on training specific effect and examining the optimal effect by modification of the training paradigms, particularly the design of the contents and level of difficulty.
published_or_final_version
Clinical Psychology
Doctoral
Doctor of Psychology

Thesis (M.A.)--Cleveland State University, 2008.
Abstract. Title from PDF t.p. (viewed on July 7, 2008). Includes bibliographical references (p. 31-36). Available online via the OhioLINK ETD Center. Also available in print.

The number of adults in the United States who are age 65 or older is rapidly increasing. With longer lifespan comes an increase in chronic diseases such as dementia, diabetes, and depression. This study used archival data from a larger study conducted at the Memory Clinic at John Peter Smith County Hospital in Ft. Worth, Texas to examine several hypotheses and research questions related to the influence of type of dementia, presence of Type II diabetes, and presence of depression on neuropsychological test performance. First, this study attempted to identify specific patterns of performance on neuropsychological measures for those with Alzheimer's dementia (AD), vascular dementia (VaD), or mild cognitive impairment (MCI). The results indicated that those with MCI perform better than those with AD or VaD on all neuropsychological measures, and that those with VaD perform better than those with AD on a measure of verbal memory. Another purpose of the study was to determine how the presence of Type II diabetes affects this pattern of functioning; the overall finding in this study was that the presence or absence of diabetes did not affect performance on measures of cognitive functioning. Additionally, the study attempted to add to literature examining the influence of depression on older adults with diabetes and/or dementia; no significant differences emerged.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008.
Title from PDF title page (viewed Sept. 23, 2009). Additional advisors: Karlene K. Ball, H. Randall Griffith, Daniel C. Marson, Sylvie Mrug, David E. Vance. Includes bibliographical references (p. 59-80).

The presence of cognitive deficits in obstructive sleep apnea (OSA) is well-documented. Specifically, short- and long-term memory, attention/vigilance, and executive function (e.g. processing speed, mental flexibility, and problem solving) are affected. Cognitive deficits in aging occur in similar areas (i.e., memory and processing speed). Given that a greater percentage of older adults experience sleep-disordered breathing as compared to middle-aged adults, it is possible that OSA may account for some of the deficits typically attributed to aging. This study investigated this hypothesis by comparing middle-aged and older adults with and without OSA on computer-based measures of cognitive performance. No effect of OSA or an interaction between OSA and age on cognitive function was found; an effect of age on processing speed, distinguishing stimuli rapidly, attention, spatial ability/mental flexibility, and both working memory and short-term visual memory was found. This study also explored whether or not cognitive function may be improved in persons with OSA by re-assessing those participants one month after treatment. An effect of treatment on improvements on processing speed, distinguishing stimuli rapidly, mental flexibility, and short term memory was found. Overall, findings reflect the ability of treatment to improve cognitive function among OSA patients, regardless of lack of deficits when compared to those without OSA.

Introduction: Cognitive impairment (CI) in older adults refers to impairment in cognition function beyond normal aging. Previous studies have reported the effect of dietary antioxidants, especially flavonoids on cognitive function in older adults, suggesting that high dietary flavonoids intake may reduce the risk of cognitive impairment. However, most of these studies were reported in Caucasian older populations in Western countries. Moreover, some studies were positive, which others were negative studies. There was no previous study regarding dietary flavonoids and cognitive impairment among Chinese older adults. Objectives: The objectives of this study were to explore the association between dietary intake flavonoids and the risk of cognitive impairment in Chinese older adults, and to identify the independent factors associated with the risk of cognitive impairment in Chinese older adults. Method: This study was a retrospective cross-sectional study, 200 patients who fulfilled the inclusion and exclusion criteria and gave written informed consent were recruited from the Geriatric clinics in Queen Mary Hospital, Hong Kong, from 11th July to 31st October 2011. All recruited subjects were invited to attend face-to-face interviews. Brief cognitive assessments by the Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were done for all subjects. Every subject also answered a detailed questionnaire on socio-demographic, type and frequency of diet items (food frequency questionnaire) and co-morbid diseases. Main outcome measure: The primary outcome measure was cognitive function, using an education-adjusted MMSE cut-off s to categorize the subjects into two groups (i.e. normal cognitive group and cognitively impaired group). Results: 200 subjects were recruited, 104 participants (37 males and 67 females) were in the normal cognitive group and 96 subjects (22 males and 74 females) were in the cognitively impaired group. The mean amount of dietary flavonoids intake of the cognitively normal group was higher than that of the cognitively impaired group (i.e. 291.84 grams/day and 240.92 grams/day respectively; p=0.006 Mann-Whitney U test). Other common dietary nutrients were also compared between the two groups. The dietary carbohydrate (p<0.001), total sugar (p<0.001), vitamin C (p=0.001) and folic acid (p<0.001) intakes were significantly related to cognitive impairment (using chi-square statistics). After adjustment for age, gender, education, exercise pattern, the dietary flavonoids intake was not independently associated with cognitive impairment. However, after adjustment for age, education level, exercise pattern and BMI, the higher to highest quartile of dietary carbohydrate intake (184.184-1176.703g/d), high total sugar intake (0.166-35.102g/d), highest quartile of vitamin C intake (139.803-900.952mg/d), the third and fourth quartiles of folic acid intake (208.899-1544.418mcg/d) were significantly associated with reduced risks of cognitive impairment. Older adults who had regular exercise (both less and more than 30 minutes per day) had lower risk of cognitive impairment than those who never did exercise (OR= 0.361, 95% confidence interval=0.167-0.784 for less than 30 minutes/d; OR=0.137, 95% confidence interval=0.048-0.396 for more than 30 minutes/d). We also found high BMI was associated with a reduced risk of cognitive impairment with an OR of 0.897 (95% confidence interval=0.816-0.987). Besides, the increasing age was also associated with cognitive impairment (OR=1.059, 95% confidence interval=1.007-1.115). Conclusion: In summary, the present study demonstrated that the dietary flavonoids intake was not significantly associated with the risk of cognitive impairment in Chinese older adults in Hong Kong.
published_or_final_version
Medicine
Master
Master of Medical Sciences

Although research has shown that the complex constructs of intelligence and personality are necessarily intertwined, studies exploring this issue in elderly individuals are rare. The importance attached to this interface in older adults becomes particularly clear in light of the debate over the cause and extent of age-related decrements in cognitive performance as well as whether such losses can be ameliorated or not, especially given societal shifts toward increased life expectancies. The present study explored the basis for shifts in personality-ability relationships in adulthood by comparing two samples of older adults, one of which was assessed in 1975 (N = 102, M age = 68.4), and the second of which was assessed in 1995 (N = 100, M age = 72.0), and a sample of younger adults (N = 100, M age = 21.8), also assessed in 1995. Each participant was administered the Holtzman Inkblot Technique and the Gf-Gc Sampler, a measure of crystallized (Gc) and fluid (Gf) abilities. LISREL analyses of both age-related and historical shifts in personality-ability relationships suggested that not only were such shifts associated with cohort differences as reflected in factor loading (lambda) differences between the older samples and the younger sample, as well as between each of the older samples, but also that such connections were weaker among younger adults. These findings are important in revealing that sociocultural shifts in opportunities for continued cognitive growth influence the impact of noncognitive (personality) factors on intellectual functioning in later life. Limitations of the current study, implications of the results, and suggestions for future research are discussed.

The purpose of the study was to validate the use of the Geriatric Functional Rating Scale (GFRS) in assessing cognitively impaired individuals 65 years of age and older to determine the need for institutionalization. The population of interest consisted of individuals 65 years of age and older exhibiting cognitive impairment and residing in Delaware County, Indiana. A nonrandomized two-group experimental design was utilized for the study. Eighty subjects were selected from two subpopulations consisting of 40 institutionalized and 40 noninstitutionalized elderly.Two geriatric assessment tools were used for the study, the Mental Status Questionnaire (MSQ) and the Geriatric Functional Rating Scale (GFRS). The hypothesis for the study stated that the mean GFRS score of the noninstitutionalized subjects, the control group, would be significantly greater than the mean score of the institutionalized subjects, the experimental group.The MSQ scores as well as the means and standard deviations for the seven subscales of the GFRS were reported for the two groups. A one-tailed t-test was used to test the hypothesis. A decision with regard to the hypothesis was made at the .05 level.Findings of the study included the following:1. The subjects ranged in age from 65 to 92 years, were 90 percent female, and predominantly Protestant, 88 percent.2. The MSQ scores for the combined groups ranged from minimal cognitive impairment, 71 percent, to severe cognitive impairment, four percent.3. The total mean score on the GFRS for the institutionalized group was 6.8 indicating a need for institutionalization.4. The total score on the GFRS of the noninstitutionalized was over 10 times higher at 70.7.5. The noninstitutionalized group scored significantly higher in the GFRS (p<.00) than the institutionalized counterparts.In conclusion, the research supports the use of the Geriatric Functional Rating Scale in assessing the need for institutionalization in cognitively impaired individuals, 65 years of age and older in Delaware County, Indiana.
Department of Educational Administration and Supervision

The frontal lobe hypothesis of ageing proposes that cognitive functions associated with the prefrontal cortex (PFC) are more susceptible to age-related changes than those supported by other brain regions (e.g., Dempster, 1992; West, 1996). Age-related declines previously demonstrated in working memory (e.g., Bopp & Verhaeghen, 2005), inhibitory control (Dempster, 1992), executive attention (e.g., West, 2004) and fluid intelligence (Horn & Cattell, 1967), have been linked to changes in PFC functioning. Relational processing also depends on the integrity of the PFC (e.g., Christoff et al., 2001), but research on age-related declines in relational processing is limited (Andrews & Todd, 2008; Viskontas, Holyoak, & Knowlton, 2005; Viskontas, Morrison, Holyoak, Hummel, & Knowlton, 2004). Unlike previous research which tended to focus on a single construct, the current research investigated age-related changes in executive attention, inhibitory control, working memory and relational processing. Distinctions within three constructs were also of interest. Three aspects of inhibitory control (response inhibition, task-set switching and inhibition in memory retrieval) were examined. Relational processing was examined in four tasks, three of which involved items at two or more levels of complexity. Working memory was examined using simple span and complex span tasks. The test battery of 16 tasks assessed these constructs as well as speed of processing, crystallized and fluid intelligence, and frontal functioning (Tower of London). It was administered to a sample of 125 normally ageing adults who ranged in age from 18 years to 92 years with all age decades represented.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Psychology
Griffith Health
Full Text

The extent of cognitive deficit in depressed elderly remains unclear. Recent follow-up studies of elderly patients diagnosed as depressed suggest that depression may present as the initial sign of progressive dementia. This raises questions regarding the nature of the depression in those individuals who deteriorate cognitively over time, and encourages the search for clinical indicators of those depressed who are likely to deteriorate. Thirty-five depressed older adult outpatients were comprehensively examined and re-evaluated with a brief neuropsychological battery after one or more years. Twenty-three probable dementia of the Alzheimer's type patients (DAT) provided a comparison with a known progressive disorder. Patients with a decline of four points from their original score on a mental status examination comprised the "depressed with cognitive deterioration" sample (N = 8) and all others made up the "depressed without cognitive deterioration" sample (N = 27). These two samples were then compared on clinical variables from the initial neuropsychological, medical, radiological, and patient history examination. A Multivariate analysis of variance using the following variables: initial age, education, modified Hachinski, initial Mini-Mental State, Wechsler Memory Quotient, vocabulary, digit span, similarities, picture completion, block design, and digit symbol subtests of the Wechsler Adult Intelligence Scale-Revised, initial Geriatric Depression Scale, and Grocery Store Test of verbal fluency failed to differentiate those depressed elderly that declined from those who did not. A series of Chi-square analyses using the medical and radiological variables demonstrated a significant association between depressed with deterioration and magnetic resonance imaging (MRI) abnormalities, computerized tomography (CT) abnormalities, and Electrocardiogram (EKG) abnormalities. Those depressed patients with cognitive deterioration demonstrated a higher frequency of white matter abnormalities on the combined CT and MRI than did those depressed patients with no deterioration. Leuko-araiosis in depressed elderly may represent a clinical marker for the identification of later cognitive deterioration. Results indicate: (1) a need for the development of more sensitive neuropsychological measures for accurate prediction of deterioration; (2) the importance of follow-up neuropsychological evaluations on depressed elderly; (3) relationship between white matter abnormality and cognitive deterioration in depressed elderly, and (4) support for the hypothesis that depression may present as an early sign of a later developing progressive dementia.

Dementia is a growing social problem in Australia because as the population ages, the incidence of dementia increases. While the prevalence rates are only about I% at age 65, they double every five years until by 85 years of age the rate is over 24%. It is expected that by the year 2030, the number of elderly people with dementia will increase by 200%. Dementia is easily recognized in its advanced stages but can be overlooked in the early phase. Family members, care-givers and even the treating medical practitioner may mistakenly attribute the early decline in mental function to the normal aging process. A diagnostic instrument that is easy to administer and score yet is sensitive and specific to the detection of cognitive impairment in the elderly may prove to be of significant benefit to clinicians and assist care-givers and family members in treatment decisions, accommodation requirements and the timely provision of a range of support services. This study investigates the use of the Cognitive Status Examination (CSE) for detecting brain impairment in elderly people. The Cognitive Status Examination comprises the Cognitive Difficulties Scale and a Letter Symbol Substitution Task. It was developed as a screening instrument to detect Alcohol Related Brain Impairment and has proved to be 80% sensitive and 88% specific in detecting brain impairment in that group. This study extended those results to males and females aged 65 years and over with early dementia. A sample of 58 community-dwelling, elderly people aged 65 years and above and a clinical sample of 44 in-patients who were diagnosed with early dementia completed the Cognitive Status Examination. An existing groups, quasi-experimental research design was used. The Cognitive Status Examination proved to be marginally useful as a screening instrument for detecting cognitive impairment in elderly people with early stage dementia with a sensitivity of 59% and a specificity of 93% when the original cut-off scores were used. A revised cut-off score, determined by trial and error, was developed. This resulted in a sensitivity of 86.2% and a specificity of 77.3%, but even with such ad hoc adjustments the CSE fell marginally short of the required 80% for both specifications. Use of the CSE may enable clinicians to utilize existing resources more effectively by referring elderly people in need to appropriate medical care, accommodation and community support services, but further research is required to confirm the revised cutting scores for the CSE. Regression analysis showed that a combination of the raw LST score and the BDI score gained over 90% sensitivity and specificity, and such an actuarial approach also shows promise for future development.

Deteriorations in cognitive functioning and sleep are the inevitable parts of the ageing process, and they are two very common complaints among the elderly population. Given their high relevance and great impact on daily functioning, many studies have attempted to address the associations of sleep problems and cognitive functioning with ageing, yet the direction of associations remained unclear. Several recent studies suggested that caffeine, a common psychostimulant present in coffee and tea, might have a beneficial effect on agerelated decline in cognitive functioning. Nonetheless, the dose-dependent effect of caffeine intake on specific domains of cognitive functioning, and the potential cost of compromised nocturnal sleep at high dose of caffeine remained to be investigated. In view of the lack of study on identifying the correlation and interaction between sleep, cognitive functioning, caffeine consumption habit, and age, this thesis reported two studies that clarified these relationships in the elderly population. Furthermore, the studies explored the possibility to utilize sleep and caffeine as a regimen to improve daytime cognitive functioning in the older population. Study 1 was a retrospective study that aimed to examine the relationship between sleep, habitual caffeine consumption, cognitive functioning, and mood in the two different age groups, the young adult and the elderly. Eighty-nine healthy elderly and forty-three healthy young adults participated in this study and completed a battery of neuropsychological assessment and a set of questionnaires. Findings revealed changes in multiple domains of sleep and cognitive functioning upon ageing. The age-related differences in sleep and cognitive functioning were correlated. Moreover, result suggested that regular caffeine consumption has a dose-dependent beneficial effect on cognitive functioning, but the effect was only observed in female. Study 2 was built on the relationship between sleep, cognitive functioning, and caffeine as found in Study 1. It aimed to investigate the effect of caffeine and daytime nap on the cognitive functioning in the healthy elderly adopting a repeated measure, double-blind, placebo-controlled design. Twenty-four healthy elderly were recruited for this study, and each of them were required to attend four experimental sessions with a one-week intersession interval. In each session, participants were required to take a rest or take a nap with or without a certain dosage of caffeine in the afternoon. Comparisons on their cognitive performance before and after the rest/ nap revealed an effect of nap and caffeine on improving subjective feeling of sleepiness and fatigue. Behavioural measurements revealed no effect on daytime nap on cognitive functioning, yet specific sleep stage and certain sleep oscillations were associated with post-nap changes in cognitive functioning. In summary, the present studies demonstrated the associations of sleep and caffeine consumption with cognitive functioning in the elderly. Habitual caffeine consumption was associated with a female-specific beneficial effect on cognitive functioning. Furthermore, daytime nap combined with the use of acute dose of caffeine might not enhance cognitive functioning, but could improve mood and well-being in the elderly. Findings from present studies suggested that further research could explore ways to maximise the benefit of napping in the elderly.
published_or_final_version
Psychology
Doctoral
Doctor of Philosophy

Background: High blood pressure (BP) is the leading risk factor for disease and mortality worldwide. However, risks associated with high BP in very old age (≥ 80 or ≥ 85 years) are not entirely understood, as the majority of scientific studies have been performed with younger populations and existing scientific knowledge about very old individuals is sometimes contradictory. Results of previous studies of very old individuals suggest that the associations of BP with mortality and stroke differ with levels of physical and cognitive function. More studies that are representative of very old individuals, including individuals with multimorbidity, that are of adequate size, involve proper adjustment, and investigate non-linear associations, are needed to investigate these issues. Systolic blood pressure (SBP) decline is common among very old individuals and has been shown to precede adverse events. Previous studies have shown that SBP change is associated with baseline SBP, age, and health-related factors, but determinants of SBP change have not been investigated using comprehensive, multivariate models. The three main aims of this thesis were to investigate, in a sample of individuals aged ≥ 85 years, 1) determinants of SBP change, 2) the association of BP with mortality risk and whether this association differs with respect to gait speed and/or Mini-Mental State Examination (MMSE) score, and 3) the association of BP with stroke risk and whether this association differs with respect to the Barthel Activities of Daily Living (ADL) index and/or MMSE score. Methods: The studies conducted for this thesis were based on data from the population-based Umeå 85+/Gerontological regional database study, which provided cross-sectional and longitudinal data on socioeconomic factors, medical conditions, drug prescriptions, and health-related assessments from 2000 to 2015. Participants were aged 85, 90, and ≥ 95 years, and lived in Västerbotten, Sweden, and Österbotten/Pohjanmaa, Finland. Follow-up assessments were conducted after 5 years. Mortality data were collected after 2 and 5 years, and stroke data were collected after 5 years, from death certificates, medical records, population registers, and the inpatient diagnosis register. Comprehensive multivariate models were developed to investigate determinants of SBP change using multiple linear regression, and to investigate associations of mortality and stroke risks with BP using Cox proportional-hazard regression models. Results: Average (± standard deviation) baseline SBP was 146 ± 23 mm Hg, and average diastolic blood pressure (DBP) was 74 ± 11 mm Hg. Within 5 years, 61% of participants had died and 10% had had incident strokes. Among participants followed for 5 years, the average annual SBP decline was 2.6 ± 5.4 mm Hg. In a multivariate model, SBP decline was associated with later investigation year (p = .009), higher baseline SBP (p < .001), baseline antidepressant drug use (p = .011), incident acute myocardial infarction during follow-up (p = .003), use of a new diuretic drug during follow-up (p = .044), and declining Barthel ADL index scores during follow-up (p < .001). In an age- and sex-adjusted analysis of the total sample, mortality risk was decreased in higher (vs. lower) BP categories (SBP ≥ 165 vs. ≤ 125 mm Hg: hazard ratio [HR] .50, p < .001; DBP 70–74 vs. 75–80 mm Hg: HR 1.32, p = .031). In a comprehensively adjusted analysis of the total sample, SBP was not associated significantly with mortality risk. The associations of SBP with mortality in the gait speed < .5 m/s subcohort corresponded with those found in the total sample. In comprehensively adjusted analyses in the gait speed ≥ .5 m/s subcohort, mortality risk increased independently with higher (vs. lower) BP (SBP ≥ 165 vs. 126–139 mm Hg: HR 2.13, p = .048; DBP > 80 vs. 75–80 mm Hg: HR 1.76, p = .026). In comprehensively adjusted analyses in the MMSE score subcohorts, SBP was associated significantly with mortality risk only in the 0–10 MMSE score subcohort; high and low SBP categories were associated independently with increased mortality risk, compared with an intermediary SBP category (SBP ≥ 165 vs. 126–139 mm Hg; HR 4.54, p = .007; SBP ≤ 125 vs. 126–139 mm Hg: HR 2.23, p = .023). Higher BP was associated significantly with increased stroke risk in multivariate models (SBP per 10 mm Hg increment: HR 1.19, p < .001; DBP per 10 mm Hg increment: HR 1.26, p = .013). SBP was not associated with stroke risk in participants with SBP < 140 mm Hg. Interaction effects on the association with mortality were significant between SBP and gait speed (age- and sex-adjusted model: p = .031) but not between SBP and MMSE score. No interaction in the association with stroke was found between any BP measure and Barthel ADL index or MMSE score. Conclusion: The decline in BP in very old age may be explained by health-related factors. Low BP may be a risk marker for short life expectancy, due to morbidity, in the general very old population and among very old individuals with low gait speeds. High BP seems to be an independent risk factor for mortality only in certain groups, which may be distinguished by high gait speed or very severe cognitive impairment. High SBP and DBP seem to increase stroke risk in very old age. These findings may contribute to a better understanding of the risks of adverse outcomes in very old individuals with different BP levels, the importance of comorbidity for these risks, and the etiology of SBP change.
Bakgrund: Högt blodtryck är den största bidragande orsaken till sjukdom och död i världen. Man har ännu inte fastslagit om högt blodtryck ökar risken för sjukdom och död även i mycket hög ålder, vilket kan definieras som 80 år och äldre. Detta beror bland annat på att endast en liten andel av forskningen hittills har fokuserat på den här åldersgruppen. Mycket gamla människor skiljer sig från yngre på olika sätt som skulle kunna påverka riskerna med högt blodtryck. Till exempel är det vanligare med sjukdomar och att ha många samtidiga sjukdomstillstånd bland mycket gamla människor än i yngre åldersgrupper. Då andelen mycket gamla människor i befolkningen ökar kraftigt får dessa frågor allt större betydelse. Det är vanligt med sjunkande blodtryck i mycket hög ålder, något som verkar föregå sjukdom och död. Tidigare studier har funnit att sjunkande blodtryck skulle kunna bero på ökande sjuklighet, högre ålder och högre begynnelseblodtryck. Man vet ännu inte vilka enskilda faktorer som bäst förklarar blodtrycksförändringen i mycket hög ålder, oberoende av andra faktorer. Tidigare studier har visat att lägre blodtryck kan vara förenat med en ökad risk för tidig död bland mycket gamla människor. Det är oklart om risken för tidig död bättre kan förklaras av andra faktorer, s.k. störfaktorer. Störfaktorer kan till exempel vara sjukdomar som både påverkar blodtrycket och risken. Fynd från tidigare studier av personer som är minst 65 år tyder på att sambandet mellan blodtryck och död kan skilja sig mellan grupper med hög eller låg gånghastighet, vilket används som ett ungefärligt mått på hälso-tillståndet. Detta skulle även kunna ha betydelse för mycket gamla människor eftersom deras hälsotillstånd kan skilja sig mycket mellan individer. Man har också utrett huruvida sambandet mellan blodtryck och död skiljer sig mellan grupper med och utan kognitiv svikt, som till exempel kan bero på demenssjukdom, men inte kommit fram till entydiga resultat. Ett fåtal studier har utrett strokerisken med högt blodtryck i mycket hög ålder. På grund av motsägelsefulla resultat är det ännu oklart om högt blodtryck ökar risken för stroke bland mycket gamla människor. Man har sett tecken på att sambandet mellan blodtryck och strokerisk skulle kunna skilja sig mellan grupper av mycket gamla människor med och utan kognitiv svikt, samt mellan grupper med och utan hjälpbehov i dagliga aktiviteter. Dagliga aktiviteter innefattar bland annat att tvätta sig, klä sig, gå på toaletten, äta och resa sig från en stol. Frågeställningar: I den här avhandlingen undersöktes huvudsakligen tre frågeställningar. Den första var vilka faktorer som påverkar hur blodtrycks-nivåerna förändras över tid i mycket hög ålder. Den andra frågeställningen var om olika blodtrycksnivåer är förenade med ökad risk för tidig död i mycket hög ålder och huruvida risken skiljer sig mellan grupper av mycket gamla människor med olika gånghastighet eller olika grader av kognitiv svikt. Den tredje frågeställningen var om olika blodtrycksnivåer är förenade med ökad risk för stroke i mycket hög ålder och om risken skiljer sig mellan grupper av mycket gamla människor med och utan kognitiv svikt eller hjälpbehov i dagliga aktiviteter. Även skillnader mellan gånghastighets-grupper testades. Metod: Avhandlingen bygger på befolkningsmaterialet Umeå85+/Gerontologisk regional databas (GERDA). Umeå85+/GERDA innehåller information från individer i åldrarna 85, 90 och 95 år och äldre, boende i Västerbotten, Sverige och Österbotten/Pohjanmaa, Finland. Informationen är insamlad vart femte år under perioden 2000-2015. Umeå85+/GERDA innehåller information om socioekonomiska faktorer, sjukdomar och läkemedel. Informationen inhämtades med hjälp av ett standardiserat frågeformulär som deltagarna besvarade under ett hembesök, samt med hjälp av journaler, boendepersonal och anhöriga. Det gjordes även hälsorelaterade mätningar och tester under hembesöken, bl.a. av blodtryck och gånghastighet i vanlig takt. Skattningsskalorna Mini-Mental State Examination (MMSE) och Barthel Activities in daily living (ADL) index användes för att skatta kognitiv funktion respektive hjälpbehov i dagliga aktiviteter. Deltagarna delades in i två gånghastighetsgrupper. Personer med högre gånghastighet (minst 0,5 m/s) utgjorde en grupp. I den andra gruppen var personer med lägre gånghastighet (under 0,5 m/s) och de som inte klarade av att genomföra testet på grund av bestående begränsningar av gångfunktionen. Deltagarna grupperades också med avseende på olika grader av kognitiv svikt. Gruppindelningen baserades på MMSE-poäng; mycket svår kognitiv svikt (0-10 poäng), svår kognitiv svikt (11-17 poäng) och mild kognitiv svikt (18-23 poäng). Deltagare utan kognitiv svikt utgjorde en egen grupp (24-30 poäng). Deltagarna delades även in i grupper med och utan hjälpbehov i dagliga aktiviteter, baserat på Barthel ADL index (under 20 respektive 20). Blodtrycksförändring observerades över tiden mellan två Umeå85+/GERDA-insamlingar, vilket var 5 år. Dödsdatum och datum för stroke inhämtades från dödsbevis, befolkningsregister, journaler och sjukvårdens diagnoskodsregister i upp till 5 år. Frågeställningarna utreddes med hjälp av statistiska metoder, baserat på materialet från Umeå85+/GERDA. Sambanden prövades med avseende på störfaktorer och skillnader mellan grupper. Resultat: Förändringar av det systoliska blodtrycket undersöktes bland 297 deltagare. I genomsnitt sjönk blodtrycket med 2,6 mm Hg per år. För nästan två tredjedelar (62%) av deltagarna sjönk blodtrycket med minst 5 mm Hg på 5 år. Ungefär en fjärdedel (26%) hade minst 5 mm Hg stigande blodtryck på 5 år. Ett antal faktorer var förenade med förändring av det systoliska blodtrycket över 5 år, oberoende av varandra. Sjunkande systoliskt blodtryck var förenat med ett högre begynnelseblodtryck, senare undersökningsår, att ha antidepressiv behandling, att få en hjärtinfarkt, att påbörja läkemedels-behandling med diuretika eller få ökat hjälpbehov i dagliga aktiviteter. Man vet ännu inte vad som är orsak och verkan i dessa samband. Frågeställningen om olika blodtrycksnivåer är förenade med ökad risk för tidig död undersöktes i ett urval av 806 deltagare. Inom 5 år avled nästan två tredjedelar (61%) av deltagarna. Risken för tidig död var mindre bland deltagare med högre blodtryck, jämfört med dem som hade lägre blodtryck. Största skillnaden uppmättes mellan deltagare med minst 165 mm Hg i systoliskt blodtryck, där risken var halverad, jämfört med dem som hade 125 mm Hg eller lägre. Detta samband verkar bero på störfaktorer, främst sjukdomar, som både orsakar lågt blodtryck och den ökade risken för tidig död. Gånghastighetsgrupperna utgjordes av 312 deltagare med högre gånghastighet och 433 med lägre gånghastighet, varav 136 inte kunde genomföra mätningen på grund av bestående begränsning av gångfunktionen. Sambandet mellan blodtryck och risken att dö inom 5 år verkade skilja sig mellan gånghastighetsgrupperna. Gruppen med lägre gånghastighet uppvisade samma samband som hela urvalet och hade ökad risk för tidig död med lägre blodtryck. Även här verkade sambandet förklaras av störfaktorer. Personer med högre gånghastighet uppvisade ett annat samband, där högre systoliskt blodtryck på minst 165 mm Hg var förenat med en fördubblad risk för tidig död, jämfört med 126-139 mm Hg. Högre diastoliskt blodtryck på över 80 mm Hg var också förenat med ökad risk för tidig död, jämfört med 75-80 mm Hg. Sambandet berodde inte på störfaktorer. Grupperna med svår, måttlig och mild kognitiv svikt innehöll 118, 166 och 289 deltagare vardera. Gruppen utan kognitiv svikt innehöll 542 deltagare. Dessa grupper verkade också skilja sig något med avseende på sambandet mellan blodtryck och risken för tidig död, men skillnaderna var inte statistiskt säkerställda. Särskilt gruppen med mycket svår kognitiv svikt uppvisade ett annorlunda samband mellan systoliskt blodtryck och risken för tidig död, jämfört med övriga deltagare. Bland dessa deltagare var risken för tidig död mer än fyrdubblad med höga blodtryck på minst 165 mm Hg, jämfört med 126-139 mm Hg. De med blodtryck 125 mm Hg eller lägre hade dubbelt så hög risk för tidig död, jämfört med 126-139 mm Hg. Dessa samband var oberoende av störfaktorer. Frågeställningen om strokerisk med högt blodtryck utreddes i ett urval av 955 deltagare. Inom 5 år fick 94 deltagare en stroke, vilket motsvarar en av tio. Högre blodtryck var förenat med ökad risk för stroke, jämfört med lägre blodtryck. Risken att få en stroke inom 5 år var fördubblad bland deltagare med högt systolisk blodtryck på minst 160 mm Hg, jämfört med under 140 mm Hg, eller med höga diastoliska blodtryck på minst 90 mm Hg, jämfört med under 90 mm Hg. Sambanden var oberoende av en mängd andra riskfaktorer. Strokerisken med högt blodtryck verkade inte påverkas av gånghastigheten, den kognitiva nivån, eller hjälpbehovet i dagliga aktiviteter. Slutsatser: Blodtrycket verkar sjunka hos de flesta i mycket hög ålder. Sjunkande systoliskt blodtryck kan till stor del förklaras av högre begynnelseblodtryck, senare undersökningsår, att ha antidepressiv läkemedelsbehandling, att få en hjärtinfarkt, att påbörja läkemedels-behandling med diuretika eller få ökat hjälpbehov i dagliga aktiviteter. Lågt blodtryck verkar i mycket hög ålder vara ett tecken på olika underliggande sjukdomsprocesser, som ökar risken att dö inom 5 år. Detta samband verkar särskilt gälla personer med lägre gånghastighet, vilket kan vara ett tecken på sämre hälsa. Högt blodtryck verkar endast vara förenat med ökad risk för tidig död i särskilda grupper, som kan utmärkas av högre gånghastighet eller mycket svår kognitiv svikt. Även lågt systoliskt blodtryck kan vara förenat med ökad risk för tidig död bland personer med mycket svår kognitiv svikt. I dessa grupper kan sambandet vara oberoende av störfaktorer. Högre blodtryck verkar vara förenat med ökad risk för stroke i mycket hög ålder, oberoende av en mängd andra sjukdomstillstånd. Det finns sannolikt en gräns för hur lågt blodtryck som är gynnsamt med avseende på strokerisken, men det är ännu inte klarlagt var den gränsen går. Sambandet mellan högt blodtryck och strokerisk verkar inte skilja sig mellan grupper med olika hög gånghastighet, kognitiv nivå, eller hjälpbehov i dagliga aktiviteter. Dessa fynd kan bidra till en bättre förståelse för blodtrycksförändring, risker med högt och lågt blodtryck i mycket hög ålder samt hälsotillståndets betydelse för dessa risker.

This study examined the relationship between perceptions of intellectual functioning and measures of cognitive abilities, personality variables and sociodemographic information. One hundred and fifty-two older community residing adults were asked to define their perception of intelligence by completing a questionnaire that asked the extent to which a variety of tasks are: functionally important, contribute to feelings of intellectual vitality and are the object of worry or concern. They also estimated their skill at performing each task. The hypothesis that cognitive abilities would best predict perceptions of cognitive functioning was moderately supported. Personality variables, specifically anxiety, were more predictive of the meaning variables than abilities.

The aim of this thesis was to investigate inter-individual variability on cognitive task performance in normal older adults. In a review of the cognitive aging literature, the implications of a differential perspective were drawn out in order to establish a theoretical and methodological basis for an investigation into variability. A number of regularly occurring patterns, identified on the basis of available reports in the literature, were used to develop a model of variability (the shuttle model). The empirically-based model was located broadly within a neuropsychological framework, and derived explanatory power from the tenets of brain reserve capacity (BRC) theory. It served to describe the bulge in interindividual variability due to aging (the shuttle bulge), and the shifting occurrence of the bulge in relation to the age axis due to cohort and task-related influences (the shuttle shift). A two phase research study was conducted in order to test hypotheses derived from the model. Phase 1 comprised between-groups analyses of normative data covering a broad range of neuropsychological tests in the domains of attention, memory, language, visual and hand motor skills, in order to examine the progression of variability effects across the adult age range. Phase 2 constituted between and within-groups analyses of normative data from a more limited number of neuropsychological tests. It included the examination of raw score distributions and the characteristics of outliers, and was undertaken to explore more closely the nature of the variability phenomena detected in the first phase of the analysis. Taken together, the results of both phases of the investigation revealed statistically significant variability effects in support of the shuttle model. There was a consistent pattern of increased variability in association with older age regardless of functional modality; frequently, in association with later old age, there was also a subsequent decrease in variability (the shuttle bulge). The age of onset of the initial increase in variability occurred earlier or later (the shuttle shift) as a function of four factors: education, gender, task challenge and age-sensitivity of task. The finding of an earlier onset of variability effects for low education, male gender, high task challenge and high age-sensitivity of task was interpreted in terms of BRC threshold theory. The clinical and social implications of the outcome were discussed with special emphasis on the need for a differential perspective on aging, as a complement to the prevailing normative tradition. It was concluded that the shuttle model has considerable heuristic value. It presents an integrative framework for understanding existing variability data and provides clear indications for future research.

The purpose of the current study was to explore the relationship between cognitive status and depression in a sample of geriatric patients. Participants included 282 geriatric patients ranging in age from 65 to 96 years who were classified according to diagnosis as: DAT, VaD, MCI, and Norm. All were referred for neurocognitive testing from the Geriatric Assessment Program (GAP) at the University of North Texas Health Science Center (UNTHSC) in Fort Worth, Texas. This study sought to identify factor structures for two versions of the GDS using a geriatric sample of cognitively impaired and intact patients. It then compared these factors to each other to determine whether the GDS-15 is truly a shorter version of the GDS-30. These were then compared to a previously determined factor structure. This study explored whether the four-factors of the GDS-30 are able to differentiate cognitive diagnostic groups. Further, this study sought to identify whether the severity of cognitive decline impacted GDS factor score for each of the cognitively impaired groups. Results revealed a two-factor model of the GDS - 15 and a four-factor model with the GDS - 30. The GDS-15 factors did not differ from the first two factors of the GDS-30. Comparison between the GDS-30 factor structure and that reported by Hall and Davis (in press) revealed no significant differences despite the inclusion of a normal, non-demented group in the current study. Comparisons of subscale scores revealed that DAT patients tended to score lower than the other groups on all but the cognitive impairment subscale. Severity level analyses indicated that as severity of deficits increases, awareness of deficits decreases. This study found that although the GDS-30 is a good screening tool for depression in geriatric patients, it is not particularly useful in differentiating cognitive status group. Also, the GDS-15 was not found to be a good substitute for the GDS-30.

Background: Prior studies regarding the risk factors of mild cognitive impairment (MCI), such as physical activity (PA) and sleep related factors in older Chinese populations are scarce, and the findings have not been consistent. Objectives: 1. To cross-sectionally and longitudinally examine the dose-response association between PA and cognitive function by Delayed Word Recall Test (DWRT) or Mini-mental State Examination (MMSE). 2. To cross-sectionally and prospectively examine the association of sleep related factors, including sleep duration, daytime napping, morning tiredness and insomnia, with cognitive function. Design: Cross-sectional and longitudinal analysis using both baseline and follow-up data from the GBCS. Methods Baseline data from 8,451 men and 22,067 women aged 50 years or above were used for the cross-sectional analysis. Among them, 4,214 men and 11,284 women participating in the second examination were included in the longitudinal analysis. Information on demographic, socioeconomic and lifestyle factors, and personal disease history was collected. Cognitive function was assessed by MMSE and DWRT under standardized protocols. Results 1. Significant dose-response relations across quintiles of metabolic equivalent value (METs) with DWRT score in participants with or without good self-rated health were found in cross-sectional analysis (all P for trend <0.001). 2. Prospectively, compared to those who were physically active, those with moderate activity or inactivity had increased risk for MCI. Regarding daily walking time, subjects with walking of 0.5 to 1 h, or ≥1 h had significantly reduced risk of MCI by 25% and 31% respectively compared with those who walked < 0.5 h per day. Subjects with low PA level at both baseline and follow-up had a significantly higher risk of MCI than those reporting PA at both baseline and follow-up. 3. Cross-sectionally, after adjustment for a range of potential confounders, an inverted U-shaped association between sleep duration and DWRT score was found, with 7 to 8 h of habitual sleep duration showing the highest score (P-values for trend from 3 to 7 h and from 7 to ≥10 h were all ≤0.001). Subjects with daily napping, morning tiredness, or insomnia had lower DWRT score than those without (P ranged from <0.001 to 0.01). 4. Prospectively, after adjustment for multiple risk factors, compared to sleep duration of 7 hours per day, those with sleep duration of 5 hours or less had increased risk for MCI by 43%. The adjusted P value for the linear trend from sleep duration of 3 hours to 7 hours per day was 0.01. The association remained after excluding those with poor health status. No significant associations of daytime napping, morning tiredness and insomnia with MCI were found. Conclusions In summary, we found a significant dose response association between PA and cognitive function in both cross-sectional and longitudinal analysis. One hour of daily walking is recommended for older Chinese people to delay or prevent cognitive decline. Short or long sleep duration may also be an important predictor of mild cognitive impairment. Sleep duration of less than 6 hours per day may indicate an increase risk of cognitive impairment in older people.
published_or_final_version
Community Medicine
Doctoral
Doctor of Philosophy

China has 9 million elderly individuals with dementia, which places it first in the world. Although family care remains the major source of support for people with dementia, residential care has become an indispensable choice in recent years. The biggest concern is the quality of life of the elderly with cognitive impairment or dementia (QOL-ECI) in residential care facilities (RCFs). Previous studies have explored many individual-level factors associated with QOL-ECI; however, less discussion has been conducted on how to improve it from an organizational-level perspective. China serves as a good research setting for this issue. The present study aims to establish an organizational-level framework to investigate QOL-ECI in RCFs. The Person-centered Care (PCC) Approach serves as an organizational strategy, and the High Commitment Work System (HCWS) is used as a human resource management practice. The study exposes the QOL-ECI status of RCFs in Xi’an China; and examines the relationship between PCC/HCWS and QOL-ECI respectively and jointly. A quantitative research method, survey in particular has been designed to achieve the research objectives, and has been conducted in two phases. Phase one of the study aims to validate a Chinese Version of the Person-centered care Assessment Tool (P-CATC), which is designed to measure the extent to which formal caregivers rate their facility as being person-centered. The resulting 24-item P-CAT-C is validated among a sample of full-time employees (n=330) in all 34 RCFs in urban Xi’an, a city in China. Phase two is a survey conducted among the same 34 RCFs. Full-time employees (n=330) evaluated the HCWS level for each RCF; residents with cognitive impairment (n=307) and their respective personal care workers (n=207) were invited to evaluate QOL-ECI. Hierarchical Linear Modeling (HLM) has been adopted to test the hypothesis. In phase one study, Confirmatory Factor Analysis (CFA) shows that a three-factor 15-item solution of the P-CAT-C provided adequate fit indices to the data (χ2 = 145.69, df = 81, p< 0.001, CFI = 0.93, TLI=0.91; RMSEA = 0.05). The internal consistency coefficient (Cronbach’s α=0.68) is satisfactory. The inter scale correlation shows good construct validity. The result of Phase two study shows that the total mean patient-rated QOL-ECI score is 36.06 (SD=8.16) and the caregiver-rated score is 34.09 (SD=6.88). Using caregiver-rated QOL-ECI as the dependent variable, the HLM regression analysis shows that PCC and HCWS are statistically significant with QOL-ECI respectively, and that the HCWS has a positive moderate effect on the relationship between PCC and QOL-ECI. Using patient-rated QOL-ECI as the dependent variable, the hypotheses are partially supported. This study is among the first to report the QOL-ECI status of RCFs in China. It initially demonstrates that PCC and HCWS are positively associated with QOL-ECI both respectively and jointly. It also primarily establishes an organizational-level framework to examine QOL-ECI. This will generate valuable implications and insight into research, practice and policy-making. Finally, this study further develops the PCC theory from an organizational perspective, and contributes to both management and social work literature by first adopting the HCWS for service organizations for the elderly.
published_or_final_version
Social Work and Social Administration
Doctoral
Doctor of Philosophy

[Truncated thesis] This thesis is concerned with executive functioning in two different but related ways. The first is as an information processing construct in cognitive psychology. There are many different conceptualisations of the information processing basis of executive functioning but this thesis will pursue the notion that executive functioning is best thought of as adaptation to novelty. In the thesis, this will be operationalised using performance indices (principally reaction time) from a number of information processing tasks. These tasks have typically been used in the literature to index either executive functioning or speed of information processing. Both kinds of tasks are used to tackle the second concern of this thesis, namely, how executive functioning is measured. The data analytic techniques developed in this thesis are based on the hypothesis that executive functioning is the process or processes involved in resolving task novelty and consequently measurement will be enhanced through an analysis of performance changes within tasks as the task changes from novel to familiar. The analysis methods will be based largely on the computation of coefficient of variation of reaction time in successive performance windows across the information processing tasks. An elderly sample was chosen for this thesis because of a history of research that has attempted to determine whether cognitive deficits in the elderly are the consequence of the slowing of information processing speed or to impairment in executive functioning. ... The analysis was driven by the hypothesis that a significant shift in the coefficient of variation would mark a transition from novelty to familiarity in task performance and hence from executive to non-executive phases. Three methods were applied to individual performance curves to determine the point at which for each task this transition occurred. Using criterion measures of variability to separate the task data into two stages, analyses showed, contrary to the hypothesis, that later task performance was more highly associated with executive functioning than in initial task performance. The fourth stage of analysis (Chapter 7) applied confirmatory factor analysis to the newly-formed pre- and post transition data. Evidence was found that the magnitude of the contributions of EF across the pre- and post-criterion phases was stable, failing to support the hypothesis. Finally, structural equation modelling was used to examine how age and intelligence in this elderly sample exerts its influence on task performance and whether EF or IPS was the primary cause of age-related cognitive decline. The results showed that the age and intelligence effects on performance were mediated by the requirement to adapt to novelty. Although there was limited evidence to claim that EF is the primary cause of age-related cognitive decline, ageing effects were only apparent when the participants were adapting to novelty. The thesis concludes that there is some support for the hypothesis that executive functioning is best thought of as the processes underpinning adaptation to novelty. While not a panacea, the analytic techniques developed show promise for future research.

Longitudinal data (N = 263) was used to investigate the bidirectional relationship between engagement (engaged lifestyle activities) and cognition (crystallized & fluid intelligence). Extroversion and openness to experience were also tested as moderators of the relationship between engagement and cognition. Results showed that the relationship between engagement at Wave 1 and cognition at Wave 2 did not differ from the relationship between cognition at Wave 1 and engagement at Wave 2. Testing for moderation with regression indicated that neither extroversion nor openness was moderating the relationship between engagement and cognition in either direction. Structural equation models provided further summary evidence that the relationships among engagement at Wave 1, extroversion, openness, and cognition at Wave 2 were not strong. However, a strong limitation to these results was the measurement error associated with a new measure of engagement.

The purpose of this research was to examine specific coping methods used by the elderly as they adjust to the environment of a long-term care facility, and to examine the correlations between these coping methods and levels of depressive symptomatology.

Today, as we live longer, dementia diseases are becoming more prevalent around the world. Thus, further knowledge of how to maintain levels of cognitive functioning in old age and how to identify factors that postpone the onset of dementia are of acute interest. Lifestyle patterns and social life are important aspects to consider in this regard. This thesis includes three studies. Study I investigated the association between participation in various leisure activities in old age (≥65 years) and risk of incident all-cause dementia. Analyses of the total follow-up time period (15 years) showed that higher levels of “Social” and “Total” leisure activity were associated with decreased risk of dementia. In Study II, the aim was to investigate the association between various aspects of social relationships in old age (≥65 years) and risk of incidents of all-cause dementia and Alzheimer's disease. Results showed that over the total follow-up period (16 years) higher values on the relationship index were associated with reduced risk of both dementia and Alzheimer's disease. Visiting/visits of friends and acquaintances more than once a week was related to decreased risk for all-cause dementia, but not for Alzheimer's disease. However, in neither Study I nor II did any of these factors alter the risk of all-cause dementia or Alzheimer's disease when near-onset dementias were removed from the analyses (Study I, up to five years; Study II, up to three years). In Study III the aim was to investigate the association between social network size and cognitive ability in a middle-aged (40–60 years) sample. The idea was that if social network size can moderate negative age-related influence on memory functions, it might also put an individual on a cognitive trajectory that is beneficial in old age. Results from longitudinal analyses showed that baseline network size was positively related to five-year changes in semantic memory and with changes in both semantic and episodic memory at the ten-year follow-up. Social network size was unrelated to changes in visuospatial performance. Taken together, enrichment factors measured in old age (≥ 65 years) did not alter the risk of all-cause dementia or Alzheimer's disease when near-onset dementias were removed from the analyses. These results might reflect protective short-term effects or reverse causality, meaning that in the prodromal phase of dementia individuals tend to withdraw from activity. Social network size in middle age (40-60 years), however, appears to have beneficial long-term effects on cognitive functioning. The results highlight the importance of long follow-up periods and the need to adjust for the influences of reverse causality when investigating the impact of a socially and mentally active life on cognitive functioning.