Добірка наукової літератури з теми "Aggressiveness in adolescence – Mathematical models"

The aim of this study was to examine the relationship among aggressiveness, parenting practices, and attachment security in adolescents, assessing maternal and paternal effects separately. Two different subsamples of adolescents between 12 and 16 years old participated in the study (n = 157): 67 adopted adolescents (61.2% girls) and 90 non-adopted adolescents (56.7% girls). Partial and full mediation models were analyzed in multi-group structural equation models (using maximum likelihood estimates), allocating non-adoptive and adoptive adolescents into two different groups. Results showed that whereas acceptance/involvement of each parent predicted attachment security towards the corresponding parental figure, only the father’s coercion/imposition predicted aggressiveness, and only attachment security to the mother was a (negative) predictor of adolescent’s aggressiveness. The partial mediation model provided the most parsimonious explanation for the data, showing no differences between adopted and non-adopted subsamples and supporting a good model fit for both boys and girls in a multi-group invariance analysis. The implications of these results are discussed in light of the protective effects of care relationships in early adolescence (vs. late adolescence) as well as the differential role of parent figures.

The aggressiveness of an extensive collection of strains of Erwinia amylovora was analyzed using immature fruit and detached pear flower assays under controlled environmental conditions. The analysis was performed by means of a quantitative approach based on fitting data to mathematical models that relate infection incidence to pathogen dose and time. Probit and hyperbolic saturation models were used for disease-dose relationships and provided information on the median effective dose (ED50). Values of ED50 ranged from 103 to 106 CFU/ml (10 to 104 CFU per site of inoculation). A modified Gompertz model was used for disease-time relationships and provided information on the rate of infection incidence progression (rg) and time delayed to start of the incidence progress curve (t0). Values of rg ranged from near 0 to 1.90, and t0 varied from 1.3 to more than 10 days. The more aggressive strains showed high rg, low ED50 values, and short t0, whereas the less aggressive strains showed low rg, high ED50, and long t 0. The aggressiveness was dependent on plant material type and pear cultivars and was significantly different between strains of E. amylovora. Infectivity titration and kinetic analysis of progression of incidence of infections using the immature pear test and a standardized scale are proposed for assessment of strain aggressiveness. The implications of rg, ED50, and t0 for the epidemiology and management of fire blight are discussed, particularly the wide range of aggressiveness among strains, the degree of host specificity observed in pear isolates, the very high infective potential of this pathogen, the independent action of pathogen cells during infection, and the possible advantage of including aggressiveness parameters into fire blight risk forecasting systems.

Digital control of breeding process, creation of mathematical models of living objects and management of plant life cycle is an urgent problem of modern times. Сreation of technologies that ensure implementation of the concept of advanced digital "smart" agriculture is impossible without basic mathematical models of "mass interactions" of natural living objects. This primarily affects the spread of certain diseases in populations. In the plant world, such a convenient model object is the well-studied "host-pathogen" system by the example of the interaction of millet and its smut disease. At present, the knowledge of the patterns of development of this disease in the millet plant is of a qualitative nature (virulence), and the quantitative characteristics (aggressiveness) are approximate. Only mathematical modeling of this process can accurately describe the development of the disease. This paper examines a probabilistic model and certain aspects of mathematical modeling using the example of identifying the laws of horizontal resistance to smut in susceptible millet genotypes.

In São Paulo State, mainly in rural areas, the utilization of wooden poles is observed for different purposes. In this context, wood in contact with the ground presents faster deterioration, which is generally associated to environmental factors and, especially to the presence of fungi and insects. With the use of mathematical models, the useful life of wooden structures can be predicted by obtaining "climatic indexes" to indicate, comparatively among the areas studied, which have more or less tendency to fungi and insects attacks. In this work, by using climatological data of several cities at São Paulo State, a simplified mathematical model was obtained to measure the aggressiveness of the wood in contact with the soil.

Abstract Background Several cytomegalovirus (CMV) vaccine candidates are under development. To reduce the burden of congenital CMV infection, potential strategies under consideration include vaccination of adult women, adolescent girls, and/or young children (both sexes). Methods We reviewed 5 studies that used infectious disease modeling to assess the potential impact of vaccination for preventing congenital CMV infection. All models assumed CMV vaccination would prevent primary infection and 2 models also assumed prevention of reinfections and reactivations. Results Despite differences in structure, assumptions, and population data, infant vaccination (both sexes) was the optimal strategy in all models, but in 1 model vaccinating seronegative women at 19–21 years of age was also optimal (for duration of vaccine protection ≥8 years). In 3 models, infant vaccination increased average age at primary infection as a result of decreased secondary transmission (herd immunity) combined with waning vaccine-induced immunity. This effect could increase the risk of congenital CMV infections in populations where primary CMV infection occurs early in childhood but could be minimized by administering a second dose of vaccine during adolescence. Conclusions Understanding vaccine efficacy and duration of immunity, and how these might vary depending on CMV serostatus and age at vaccination, will be key to defining CMV vaccination strategies.

Abstract Background Gliomas manifest in a variety of histological phenotypes with varying aggressiveness. The etiology of glioma remains largely unknown. Taller stature in adulthood has been linked with glioma risk. The aim of this study was to discern whether this association can be detected in adolescence. Methods The cohort included 2 223 168 adolescents between the ages of 16 and 19 years. Anthropometric measurements were collected at baseline. Incident cases of glioma were extracted from the Israel National Cancer Registry over a follow-up period spanning 47 635 745 person-years. Cox proportional hazard models were used to estimate the hazard ratio (HR) for glioma and glioma subtypes according to height, body mass index (BMI), and sex. Results A total of 1195 patients were diagnosed with glioma during the study period. Mean (SD) age at diagnosis was 38.1 (11.7) years. Taller adolescent height (per 10-cm increase) was positively associated with the risk for glioma of any type (HR: 1.15; P = .002). The association was retained in subgroup analyses for low-grade glioma (HR: 1.17; P = .031), high-grade glioma (HR: 1.15; P = .025), oligodendroglioma (HR: 1.31; P = .015), astrocytoma (HR: 1.12; P = .049), and a category of presumed IDH-mutated glioma (HR: 1.17; P = .013). There was a trend toward a positive association between height and glioblastoma, however this had borderline statistical significance (HR: 1.15; P = .07). After stratification of the cohort by sex, height remained a risk factor for men but not for women. Conclusions The previously established association between taller stature in adulthood and glioma risk can be traced back to adolescence. The magnitude of association differs by glioma subtype.

We study a family of deterministic models for highway traffic flow which generalize cellular automaton rule 184. This family is parameterized by the speed limit m and another parameter k that represents a "degree of aggressiveness" in driving, strictly related to the distance between two consecutive cars. We compare two driving strategies with identical maximum throughput: "conservative" driving with high speed limit and "aggressive" driving with low speed limit. Those two strategies are evaluated in terms of accident probability. We also discuss fundamental diagrams of generalized traffic rules and examine limitations of maximum achievable throughput. Possible modifications of the model are considered.

PurposeThe purpose of this paper is to study the influence of the cutting conditions (cutting speed, feed rate and cutting depth) on the roughness (Ra) and on the flank wear (Vb) of the steel AISI 4140.Design/methodology/approachMixed ceramic (CC650) and polycrystalline cubic boron nitride (PCBN) have been used to carry out straight turning tests under dry conditions.FindingsThe results indicate that PCBN is more efficient than mixed ceramic (Al2O3+TiC) used in terms of wear resistance regardless of the aggressiveness of the AISI 4140 at 50 hardness rockwell (HRC). Consequently, it is the most powerful. Surface quality attained with PCBN tool considerably compares with that of grinding. Even when the tool wear VB reached 0.3 mm, the majority of the recorded Ra values did not exceed 1 m at the various speeds tested. The correlation of tool wear Vb and surface roughness Ra established allows obtaining experimental empirical data on the cutting tool wear from measured surface roughness for practical use in industry. The values of constants and the coefficient of determinationR2of this mathematical model will be calculated. Mathematical models expressing the relation between the elements of the cutting regime and technological parameters (tool life and roughness) are proposed.Originality/valueMany works have been already made in the similar manner, but this study of CC650 and PCBN wear is the first. Through this study, we propose a mathematical model expressing the relation between the elements of the cutting regime, tool life and roughness.

Background Prior research has underscored negative impacts of perinatal parental depression on offspring cognitive performance in early childhood. However, little is known about the effects of parental depression during adolescence on offspring cognitive development. Methods and findings This study used longitudinal data from the nationally representative China Family Panel Studies (CFPS). The sample included 2,281 adolescents aged 10–15 years (the median age was 13 years with an interquartile range between 11 and 14 years) in 2012 when their parents were surveyed for depression symptoms with the 20-item Center for Epidemiologic Studies Depression Scale (CES-D). The sample was approximately balanced by sex, with 1,088 females (47.7%). We examined the associations of parental depression in 2012 with offspring cognitive performance (measured by mathematics, vocabulary, immediate word recall, delayed word recall, and number series tests) in subsequent years (i.e., 2014, 2016, and 2018) using linear regression models, adjusting for various offspring (i.e., age, sex, and birth order), parent (i.e., parents’ education level, age, whether living with the offspring, and employment status), and household characteristics (i.e., place of residence, household income, and the number of offspring). We found parental depression during adolescence to be significantly associated with worse cognitive performance in subsequent years, in both crude and adjusted models. For example, in the crude models, adolescents whose mothers had depression symptoms in 2012 scored 1.0 point lower (95% confidence interval [CI]: −1.2 to −0.8, p < 0.001) in mathematics in 2014 compared to those whose mothers did not have depression symptoms; after covariate adjustment, this difference marginally reduced to 0.8 points (95% CI: −1.0 to −0.5, p < 0.001); the associations remained robust after further adjusting for offspring earlier cognitive ability in toddlerhood (−1.2, 95% CI: −1.6, −0.9, p < 0.001), offspring cognitive ability in 2012 (−0.6, 95% CI: −0.8, −0.3, p < 0.001), offspring depression status (−0.7, 95% CI: −1.0, −0.5, p < 0.001), and parents’ cognitive ability (−0.8, 95% CI: −1.2, −0.3, p < 0.001). In line with the neuroplasticity theory, we observed stronger associations between maternal depression and mathematical/vocabulary scores among the younger adolescents (i.e., 10–11 years) than the older ones (i.e., 12–15 years). For example, the association between maternal depression and 2014 vocabulary scores was estimated to be −2.1 (95% CI: −2.6, −1.6, p < 0.001) in those aged 10–11 years, compared to −1.2 (95% CI: −1.6, −0.8, p < 0.001) in those aged 12–15 years with a difference of 0.9 (95% CI: 0.2, 1.6, p = 0.010). We also observed a stronger association of greater depression severity with worse mathematical scores. The primary limitations of this study were the relatively high attrition rate and residual confounding. Conclusions In this study, we observed that parental depression during adolescence was associated with adverse offspring cognitive development assessed up to 6 years later. These findings highlight the intergenerational association between depression in parents and cognitive development across the early life course into adolescence.

Influenza is a major challenge to global healthcare due to its high transmissivity and ability to cause major epidemics. Influenza epidemics and pandemics are associated with changes in the society structure that contribute to the spread of new viral strains in certain environmental and social settings. Currently, influenza is one of the most common global diseases that results in annual epidemics or even pandemics, often leading to lethal outcome. Influenza viruses are uniquely prone to variability via point mutations, recombination and gene reassortment accompanied with changes in their biological properties considered as the main cause of uncontrolled infection spread. Hence, examining cohorts of predisposed individuals by using probability models provides not only additional information about viral outbreaks, but also allows monitoring dynamics of viral epidemics in controlled areas. Understanding influenza epidemiology is crucial for restructuring healthcare resources. Public healthcare service mainly relies on influenza vaccination. However, there are vulnerable cohorts such as elderly and immunocompromised individuals, which usually contain no protective antiinfluenza virus antibody level. Despite advances in the developing vaccines and chemotherapy, large-scale influenza epidemics still continue to emerge. Upon that, no reliable methods for disease prognosis based on rate of ongoing epidemic situation are currently available. Monitoring and predicting emerging epidemics is complicated due to discrepancy between dynamics of influenza epidemics that might be evaluated by using surveillance data as well as platform for tracking influenza incidence rate. However, it may be profoundly exacerbated by mutations found in the influenza virus genome by altering genuine morbidity dynamics. Use of probabilistic models for assessing parameters of stochastic epidemics would contribute to more accurately predicted changes in morbidity rate. Here, an SIR+A probabilistic model considering a relationship between infected, susceptible and protected individuals as well as the aggressiveness of external risks for predicting changes in influenza morbidity rate that allowed to evaluate and predict the 2016 ARVI influenza incidence rate in Moscow area. Moreover, introducing an intensity of infection parameter allows to conduct a reliable analysis of incidence rate and predict its changes.

[Truncated abstract] The overall aim of the research reported in this thesis was to explore the viability and utility of the construct of psychopathy and aggression in children and adolescents. Specifically, by taking a developmentally informed approach it sought to develop new instrumentation which measured psychopathic-like-traits, and verbal proactive and reactive aggression in non-referred mainstream school children and adolescents. To achieve this, four separate yet interrelated studies were conducted. Study One comprised three phases relating to the development and validation of two new instruments. In Phase One the instruments currently used to measure psychopathy were reviewed and items relevant to young persons were selected for inclusion in a draft version of the new psychopathy screening instrument. Phase Two, which sought to further explore the construct of psychopathy in children and adolescents, comprised a series of interviews with school principals, deputy principals, psychologists, and education officers at the main juvenile detention centre in Perth, Western Australia. These interviews provided information relating to the behaviour and characteristics of children and adolescents who present with psychopathic-like-traits. As a consequence of the feedback from the Phase Two data, Phase Three reviewed the instrumentation currently used to measure aggression in children and adolescents. From this items were selected for possible inclusion in an aggression questionnaire. The data gathered over these three phases resulted in 117 psychopathy related items being generated for the new instrument, which were subsequently reduced to 56 when duplicated items were identified and the extant knowledge of the construct applied. The 56 items were retained in a draft version of the newly developed instrument, which was named the Child and Adolescent Psychopathy Screening Instrument (CAPSI). The Study One data revealed the instrumentation used to date provided few measures of physical and verbal aggression - a characteristic of psychopathic-like behaviour. Thus, a review of instrumentation together with the information from the interviews resulted in 63 aggression items being generated. ... Study Four utilised information from the CAPSI and the CASA in conjunction with in-depth interviews to generate case studies to further elucidate the characteristics of children and adolescents with psychopathic-like-traits and extreme aggression. Case studies were undertaken with seven male students ranging in age from 8 to 15 years who had been suspended from mainstream schools. All boys scored very highly on the new instruments. All presented with extreme aggression, with some exhibiting proactive or premeditated aggression combined with a superficially engaging personality, insincere charm, lack of remorse, and lack of empathy. The findings from all four research studies are discussed in the light of the literature reviewed and the aims of the research. Implications are then drawn for researchers and clinicians, and directions for further research are suggested.

Thesis (Ph. D.)--Illinois State University, 2001.
Title from title page screen, viewed March 30, 2006. Dissertation Committee: Graham A. Jones, James Cottrill (co-chairs), Linnea Sennott. Includes bibliographical references (leaves 107-111) and abstract. Also available in print.

Thesis (MSc)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Adolescents are regarded as a high risk group in South Africa with the highest human immunodeficiency virus (HIV) incidence occurring in this group. Prevention among adolescents is therefore a key in decreasing the HIV burden. This thesis aims to assist in the design of trials by simulating the potential outcomes of a combination prevention trial in adolescents. We develop a stochastic individual-based model stratified by sex and age. We then use this model to determine the impact of various prevention packages on HIV incidence among adolescents participating in a hypothetical trial over a three year period. The trial that is simulated involves an intervention arm, in which adolescents are offered a choice of a prevention methods (including medical male circumcision (MMC), oral pre-exposure prophylaxis (PrEP) and antiretroviral-based vaginal microbicides (ARV-VM)), and a control arm. We predict that the impact of a full prevention package on HIV incidence would be a 46% per personyear( PPY) (95% CI 45–47%) risk reduction. The combination of MMC and PrEP has a substantial impact on HIV incidence in males, with a 51% PPY (95% CI 49–53%) relative risk of HIV infection. Offering women the choice of PrEP, a microbicide gel or a microbicide in the form of a vaginal ring would be less effective, with a 57% PPY (95% CI 56–58%) relative risk of HIV acquisition. This is not substantially different from the relative risk estimated when the vaginal ring alone is offered, as the ring is assumed to be the most accept able of the three prevention methods. We determine a sample size requirement of approximately 1013 in each arm of a trial would achieve 80% power to detect a statistically significant reduction in HIV risk. We find that the relative risk is sensitive to the assumed degree of correlation between condom use and the acceptability of the prevention method. We also find that the most efficient trial design may be to offer both MMC and PrEP to males but to offer only a microbicide ring to females. Further work is required to better understand the processes by which adolescent prevention method choices are made.
AFRIKAANSE OPSOMMING: Adolessente word beskou as ‘n hoe risiko groep in Suid Afrika, met die hoogste menslike immuniteitsgebrekvirus (MIV) insidensie in hierdie groep. Voorkoming van MIV onder adolessente is daarom noodsaaklik om die MIV las te verminder. Die doel van hierdie tesis is om te help met die ontwerp van studies deur die moontlike uitkomste van ‘n kombinasie-voorkoming studie in adolessente te simuleer. Ons het ‘n stogastiese individu-gebaseerde model, gestratifiseer met betrekking tot seks en ouderdom, ontwikkel. Ons het toe die model gebruik om die impak van ‘n verskeinheid van voorkomingspakette op MIV insidensie onder adolessente wat deelneem aan ‘n hipotetiese proef oor ‘n drie jaar periode, te bepaal. Die proef wat gesimuleer word behels a intervensie groep, waarin die jong volwassenes ‘n keuse van voorbehoedings metodes (insluitende mediese manlike besnydenis (MMB), pre-blootstelling profilakse (PrBP) en anti-retrovirale vaginale mikrobisiedes (ARV-VM)) aangebied word, en ‘n kontrole groep. Ons voorspel dat die impak van ‘n volle voorkomingspaket op MIV insidensie ‘n 46% per persoon-jaar (PPJ) (95% VI 47–47%) risiko vermindering sal wees. Die kombinasie van MMB en PrBP het ‘n substansiele impak op MIV insidensie onder mans, met ‘n relatiewe risiko van MIV infeksie van 51% PPJ (95% VI 49–53%). Om die keuse van PrBP, ‘n mikrobisiede gel of ‘n mikrobisiede in die vorm van ‘n vaginale ring aan vrouens te bied, is minder effektief, met ‘n relatiewe risiko van MIV infeksie van 57% PPJ (95% VI 56%–58%). Hierdie verskil nie substansieel van die beraamde relatiewe risiko in die geval waar slegs die vaginale ring gebied word nie, aangesien daar aanvaar word dat die ring die mees aanvaarde van die drie voorkomingsmetodes is. Ons het bepaal dat ‘n steekproef van ongeveer 1013 individue in elke arm van die proef nodig is om ‘n 80% kans te he om ‘n statisties betekenisvolle afname in MIV-risiko te bespeur. Ons vind dat die relatiewe risiko sensitief is tot die aanvaarde graad van die korrelasies tussen kondoom-gebruik en die aanvaarding van die voorkomings metodes. Ons het ook gevind dat dit mag wees dat die mees doeltreffende proef ontwerp is om beide MMB en PrBP vir mans en slegs ‘n mikrobisiede ring vir vrouens te bied. Verdere werk word benodig om die prosesse waarby jong volwassenes keuses maak oor voorkomingsmetodes te verstaan.

O excesso de gordura corporal esta associado a diversas doenças de ordem metabólica, psicológica e estrutural. É indicado que a adolescência é o período crítico para o desenvolvimento de hábitos associados ao acúmulo de gordura como a inatividade física, má alimentação e sedentarismo. Desta forma, esta é uma fase crítica para o monitoramento da população visando a redução de casos de obesidade e doenças associadas. A técnica padrão-ouro para avaliação da gordura corporal é a absorciometria de raios-X de dupla-energia. Porém seu caráter laboratorial impede o uso amplo. Desta forma, técnicas mais simples, como a medição de dobras cutâneas devem ser modeladas a partir de técnicas mais exatas para este monitoramento. Os modelos existentes foram desenvolvidos com populações estrangeiras que não se assemelham aos habitantes da Região Metropolitana de Curitiba o que pode levar a erros de avaliação e diagnóstico. Desta forma o objetivo deste estudo é produzir um modelo de análise da gordura corporal apropriado a crianças e adolescentes da Região Metropolitana de Curitiba. Foram selecionadas duas amostras, uma composta por 567 adolescentes hígidos com idade entre 10 e 18 anos; e outra composta por 63 crianças com paralisia cerebral entre 3 e 10 anos. Os dois grupos possuíam indivíduos de ambos os sexos. Foram coletados dados de massa, estatura, idade e espessura de dobras cutâneas, além da avaliação de composição corporal por densitometria radiológica. O percentual de gordura obtido por diferentes equações de dobras cutâneas e demais medidas antropométricas entre os adolescentes foi comparado com o obtido por densitometria indicando associações abaixo do indicado (CCC<0,900). Foi encontrada também uma tendência de subestimação pelas dobras cutâneas, o que resultava em elevados valores de especificidade e baixos de sensibilidade (sendo especificidade á quantidade relativa de verdadeiros negativos entre quem não possui a condição clínica, e a sensibilidade a relação de verdadeiros positivos entre quem possui a condição considerada). Isto indica uma grande quantidade de falsos negativos o que leva muitos adolescentes com excesso de gordura a serem classificados como eutróficos. O modelo classificatório desenvolvido para adolescentes obteve um ajuste de R2 Negelkerke=0,829, sensibilidade de 99,0% e especificidade de 82,7% apresentando indicadores diagnósticos acima do obtido por equações de dobras cutâneas e IMC. Para as crianças com paralisia cerebral foi desenvolvido um modelo estimativo da massa de gordura com ajuste de R2 =0,950 com erro padrão de estimativa de 1,039. As equações utilizadas para converter as dobras cutâneas em medições da gordura corporal demonstraram-se inadequadas para aplicação em adolescentes da região metropolitana de Curitiba. A aplicação de técnicas de regressão logística e linear apresentou resultados positivos, mesmo a partir da modelagem na amostra de crianças com paralisia cerebral.
The overfat is associated with many methabolic, psycological and structural diseases. The adolescence is indicated as the critical period for the development of habits associated with fat accumulation like physical inactivity, poor diet and sedentarism. Thus, this is a important moment to monitorig the population aiming the reduction of obesity and associated disease. The golden standard to evaluate the body fatness is the dual-energy x-ray absorptiometry. However, its laboratorial aspect prevents a wide use. This way, simpler techniques as the skinfold measurement should be model from more exact techniques for this monitoring. The existing models were developed with foreign populations that don't resemble the Curitiba Metropolitan Region habitants. This could lead to evaluation and diagnostic errors. Thus, the aim of this study is to product a model of body fatness analysis appropriate to children and adolescents from the Curitiba Metropolitan Region. Two sample were selected, the first one composed by 567 healthy adolescents aged between 10 and 18 years; the other one composed by 63 children with cerebral palsy between 3 and 10 years. The groups have both genders. The data of weight, height, age and skinfold thickness were collected, beyond the body composition evaluation by radiologic densitometry. The fatness percentage obtained by different skinfold and other anthopometric mesures equations among the adolescents was compared with the obtained by densitometry presenting associations below indicated (CCC<0,900). A tendency of underestimation by the skinfold equations was found, that resulted in higher specificity values and low sensitivity (being specificity the relative quantity of true negatives among those who do not have de clinical condition, and the sensitivity the relations of true positives amons those who have the considered condition). This indicates a major quantitaty of false negatives, that leads many overfat adolescents to be classify as eutrophic. The developed classificatory model for adolescents obtained an adjustment of R2 Negelkerke=0,829, sensitivity of 99,0% and specificity of 82,7% presenting diagnostic's indicators above that obtained by skinfold equations and BMI. For the children with cerebral palsy was developed a fat mass estimation model with adjustment of R2 =0,950 and standard error of estimative of 1,039. The equations used to convert the skinfold in body fatness measures were found to be inadequate for aplication in adolescents from Curitiba Metropolitan Region. The aplication of logistic and linear regression techniques have presented positive results, even from modeling in the children with cerebral palsy sample.

Introdução: Estudos têm encontrado uma transição da obesidade da população adulta para crianças e adolescentes, que por sua vez, pode acarretar manifestações clínicas, como: doenças coronarianas, diabetes tipo 2, e complicações psicossociais cada vez mais precocemente. Contudo, métodos para avaliação da composição corporal para essa faixa etária, principalmente envolvendo técnicas de baixo custo como as medidas de dobras cutâneas (DC) apresentam imprecisões em estudos brasileiros. Fator o qual pode levar a uma interpretação equivocada da composição corporal dos avaliados. Objetivo: desenvolver novos modelos matemáticos utilizando medidas de DC, tendo como referência a absorciometria de raios-X de dupla energia (DXA), para estimativa de massa de gordura (G) em adolescentes. Métodos: Trata-se de um estudo exploratório descritivo onde foram avaliados 416 adolescentes do gênero masculino de 12 a 17 anos, sendo 42 destinados para compor a amostra de validação da pesquisa. Foram coletadas medidas de massa corporal total, estatura, circunferência da cintura e quadril, nove pontos anatômicos baseados em DC: bíceps, tríceps, subescapular, peitoral, axilar média, abdominal, supra-ilíaca, coxa e panturrilha, além da G e densidade mineral óssea (DMO) aferida com a tecnologia de DXA. Para o desenvolvimento das equações foi utilizado um modelo de regressão linear múltipla através do método de mínimos quadrados ordinários (OLS). Resultados: O grupo apresentou índice de massa corporal (IMC) médio de 21,25±4,12kg/m² e %G = 20,57±5,80%. A partir do %G, a prevalência de excesso de gordura foi verificada em 38,3% dos adolescentes. O impacto da gordura na DMO dos adolescentes indicou uma associação na ordem de r = -0,358; p<0,005, sendo verificada redução de até 14% da DMO para a região da coluna em adolescentes com obesidade em comparação aos eutróficos. O desenvolvimento de novos modelos matemáticos que atendessem critérios de alto coeficiente de determinação (R²), baixo erro padrão de estimativa (EPE), controle de colinearidade, normalidades dos resíduos, homoscedasticidade e praticidade, possibilitaram a apresentação de três opções com R² = 0,932 e EPE 1,79; R² = 0,912 e EPE = 1,78; R² = 0,850 e EPE = 1,87, respectivamente. Em todas as opções, as variáveis idade e estatura foram empregadas, bem como as DC de tríceps e subescapular. Conclusão: Os resultados obtidos evidenciam a possibilidade de desenvolvimento de novos modelos matemáticos para a avaliação da gordura corporal em adolescentes com resultados superiores aos modelos existentes na literatura.
Introduction: Studies have found a transition from obesity of the adult population to children and adolescents, which in turn, can lead to clinical manifestations, such as: coronary diseases, type 2 diabetes, and psychosocial complications increasingly early. However, methods for evaluating nutritional status for this age group, mainly involving low cost techniques such as skinfold thickness measurements (ST), are imprecise in Brazilian studies. Factor which can lead to a mistaken interpretation of the body composition of the evaluated ones. Objective: To develop new mathematical models, based on DC measurements, based on dual energy X-rays absorptiometry (DXA), to estimate fat mass (G) in adolescents. Methods: This was an exploratory descriptive study in which 416 male adolescents aged 12 to 17 years were evaluated, 42 of whom were separated to compose the study validation sample. Measurements of total body mass, stature, waist and hip circumference were obtained, nine anatomical points based on ST: biceps, triceps, subscapular, pectoral, mid axillary, abdominal, suprailiac, thigh and calf muscles, as well as G and bone mineral density (BMD) measured with DXA technology. For the development of the equations, a multiple linear regression model was used by the ordinary least square (OLS) method. Results: The group had a mean body mass index (BMI) of 21.25± 4.12 kg / m² and %G = 20.57 ± 5.80%. From %G, the prevalence of excess fat was verified in 38.3% of adolescents. The impact of fat on adolescent BMD indicated an association in the order of r = -0.358; P <0.005, with BMD reduction up to 14% for the spine region in adolescents with obesity compared to eutrophic. The development of new mathematical models that meet criteria of high coefficient of determination (R²), low standard error of estimation (SEE), control of colinearity, residue normalities, homoscedasticity and practicality, allowed the presentation of three options with R² = 0.932 and SEE 1.79; R² = 0.912 and SEE = 1.78; R² = 0.850 and SEE = 1.87, respectively. In all the options, the variables age and height were employed, as well as triceps and subscapular ST. Conclusion: The results obtained evidenced the possibility of developing new mathematical models for the evaluation of body fat in adolescents with results superior to the existing models in the literature.