Genetic and environmental factors affecting self-esteem from age 14 to 17: a longitudinal study of Finnish twins

BACKGROUND: We analysed genetic and environmental influences on self-esteem and its stability in adolescence. METHOD: Finnish twins born in 1983-1987 were assessed by questionnaire at ages 14 (n = 4132 twin individuals) and 17 years (n = 3841 twin individuals). Self-esteem was measured using the Rosenberg global self-esteem scale and analyzed using quantitative genetic methods for twin data in the Mx statistical package. RESULTS: The heritability of self-esteem was 0.62 [95% confidence interval (CI) 0.56-0.68] in 14-year-old boys and 0.40 (95% CI 0.26-0.54) in 14-year-old girls, while the corresponding estimates at age 17 were 0.48 (95% CI 0.39-0.56) and 0.29 (95% CI 0.11-0.45). Rosenberg self-esteem scores at ages 14 and 17 were modestly correlated (r = 0.44 in boys, r = 0.46 in girls). In boys, the correlation was mainly (82%) due to genetic factors, with residual co-variation due to unique environment. In girls, genetic (31%) and common environmental (61%) factors largely explained the correlation. CONCLUSIONS: In adolescence, self-esteem seems to be differently regulated in boys versus girls. A key challenge for future research is to identify environmental influences contributing to self-esteem during adolescence and determine how these factors interact with genetic influences.     

北京市顺义区中小学生饮食行为与超重肥胖的相关性分析

目的 了解顺义区中小学生饮食行为与超重肥胖之间的相关关系,有效引导中小学生合理饮食行为,为保障其健康成长提供依据。方法 采用多层整群随机抽样方法,于2017年7月对顺义区1212名中小学生进行问卷调查,对相关因素进行Logistic 多元回归分析。结果 学生超重肥胖检出率为35.53%,其中男生为42.66%,女生为28.87%,差异有统计学意义(?字2=24.852,P＜0.01);多因素分析显示,男性是学生超重肥胖的危险因素（OR=1.863,95%CI=1.455~2.384）;而吃早餐是学生超重肥胖的保护因素,包括天天吃早餐（OR=0.164,95%CI=0.058~0.464）,有时吃早餐（OR=0.166,95%CI=0.058~0.478）。结论 顺义区中小学生超重肥胖率较高,健康饮食行为与超重肥胖之间存在相关关系,各部门应加强营养和健康知识教育,保障学生健康成长。     

Hay fever – a Finnish nationwide study of adolescent twins and their parents

Background Like other atopic diseases, hay fever is known to cluster in families. This clustering is due either to effects of a shared family environment or to genetic inheritance. By comparing the occurrence of hay fever among monozygous (MZ) and dizygous (DZ) twin pairs, we were able t o estimate the contribution of genetic and environmental factors in the development of hay fever.
Methods A questionnaire mailed to a nationwide sample of 2483 families with 16-year-old twins furnished data for the cumulative incidence of physician-diagnosed hay fever among these adolescents and their parents. Results Among the 1765 twin pairs with data available for analysis, hay fever was reported for 14.1% of boys (95% CI = 12.4-15.8%) and 10.0% of girls (95% CI=8.6-11.4%). The MZ twin pairs (probandwise concordance rate=60.3%, 95% CI=52-68%) were significantly more concordant for hay fever than were DZ twin pairs (31.5%, 95% Cl=26-36%). Genetic factors accounted for 74-82% of the interindividual variability in liability to hay fever, variation in shared family environment for 7% at most, and unique (individual) environment for 18%.
Conclusions Familial occurrence of hay fever is mainly due to genes predisposing to the trait. Environmental exposures shared in common by family members but varying between families appear to account for at most a modest proportion of the variability in risk of developing hay fever.     

Genetic and Environmental Causes of Tracking in Explosive Strength during Adolescence

Purpose: To determine whether the observed phenotypic stability in explosive strength during adolescence, as measured by inter-age correlations in vertical jump (VTJ), is mainly caused by genetic and/or environmental factors. Methods: Subjects are from the Leuven Longitudinal Twin Study (LLTS) (n = 105 pairs, equally divided over five zygosity groups). VTJ data were aligned on age at peak height velocity (APHV) to attenuate the temporal fluctuations in inter-age correlations caused by differences in timing of the adolescent growth spurt. Simplex models were fitted using structural equation modelling. Results: After aligning the data on APHV, the annual inter-age correlations show a clear simplex structure over a 4 year interval. The best fitting models included additive genetic and unique environmental sources of variation. Heritability estimates ranged between 60.8% (CI 37.7%–77.2%) and 87.3% (CI 74.2%–94.0%) for boys and between 76.5% (CI 56.7%–89.0%) and 88.6% (CI 77.8%–94.1%) for girls. Up to 56.4% and 62.8% of the total variation at the last measurement occasion is explained by additive genetic factors that already explained a significant amount of variation at previous measurement occasions in boys and girls respectively. It thus can be concluded that the observed stability of explosive strength during adolescence is mainly caused by a stable genetic influence in boys and girls. Conclusions: Additive genetic factors seem to be the main cause of the observed phenotypic stability in VTJ performance in boys and girls during adolescence.     

Lower mother-to-child HIV-1 transmission in boys is independent of type of delivery and antiretroviral prophylaxis: the Italian Register for HIV Infection in Children

The relationship between infant's gender and rate of HIV-1 mother-to-child transmission (MTCT) was evaluated in a prospective cohort of 4151 children (2166 boys and 1985 girls) born to HIV-1-infected mothers enrolled in the Italian Register for HIV Infection in Children. Logistic regression models were performed to estimate crude odds ratios (ORs) and adjusted odds ratios (AORs) and 95% CIs for factors potentially influencing MTCT separately for the period 1985-1995 and the period 1996-2001. To evaluate rates of MTCT by gender in specific subgroups, separate logistic regression models by mode of delivery and antiretroviral prophylaxis were performed. Among children born in 1985-1995, 15.5% boys (95% CI: 13.6-17.7) and 17.9% girls (95% CI: 15.7-20.3) were infected (P = 0.1181). After 1995, a lower proportion of boys (3.1% [95% CI: 2.0-4.4]; AOR: 0.43 [95% CI: 0.26-0.71], P = 0.0008) than girls (AOR: 6.3%, 95% CI: 4.8-8.1) was infected. Lower AORs for boys persisted independently of elective cesarean delivery (AOR: 0.31, 95% CI: 0.14-0.71); other than elective cesarean (AOR: 0.38, 95% CI: 0.19-0.78) and antiretroviral prophylaxis (zidovudine monotherapy (AOR: 0.11, 95% CI: 0.03-0.38); none (AOR: 0.43, 95% CI: 0.21-0.90). No difference was observed when combined therapy in the mother was administered (AOR: 1.14, 95% CI: 0.30-4.32), but results were likely to be biased by the very low rate of infected children in this group. A lower proportion of HIV-1-infected boys in children born after 1995 was found. Factor(s) intrinsic to gender (rather than type of delivery or maternal antiretroviral prophylaxis) may be involved, because the risk of infection in boys was lower independent of interventions. A possible explanation is that, among infected fetuses, more girls survive up to the end of pregnancy and may take advantage of the benefits of preventive strategies.     

Interactions between breast-feeding, specific parental atopy, and sex on development of asthma and atopy

BACKGROUND: The influence of breast-feeding on the risk of developing atopy and asthma remains controversial. OBJECTIVE: To examine asthma and atopy outcomes by sex, reported specific parental history of atopy, and breast-feeding. METHODS: In a birth cohort, we examined childhood asthma and atopy (positive skin prick tests) by sex and breast-feeding in relation to maternal and paternal atopy. Interactions were explored in logistic regression models. RESULTS: For boys, breast-feeding (odds ratio [OR], 1.63; 95% CI, 0.93-2.87; P = .09) and maternal atopy (OR, 1.95; 95% CI, 0.93-4.08; P = .08) were each associated with atopy at age 13 years. Breast-feeding increased the risk for atopy among boys with paternal atopy (OR, 7.39; 95% CI, 2.21-24.66) compared with non-breast-fed boys with paternal atopy, but did not significantly further increase risk among subjects with maternal atopy. For girls, breast-feeding (OR, 0.74; 95% CI, 0.41-1.31) and maternal and paternal atopy were not independent risk factors for atopy at age 13 years. However, breast-feeding increased the risk for atopy in girls with maternal atopy (OR, 3.13; 95% CI, 1.20-8.14) compared with non-breast-fed girls with maternal atopy. There was no such effect among subjects with paternal atopy. Results for the outcome of asthma followed a similar pattern. CONCLUSION: The influence of breast-feeding on development of atopy and asthma differs by sex and by maternal and paternal atopy, and is most significant among subjects at lower baseline risk. CLINICAL IMPLICATIONS: Analyses of environmental risk factors for asthma and atopy should be stratified by specific parental atopy and sex.     

Epidemiology of abdominal obesity among adolescents from a Brazilian State Capital

The objective of this study was to investigate the effects of socioeconomic, demographic and lifestyle factors on abdominal obesity in adolescents from a Brazilian state capital. In this cross-sectional study, 656 high school students (423 girls and 233 boys) from public schools, ranging in age from 14 to 19 yr, were evaluated. Abdominal obesity was identified based on waist circumference. Socioeconomic data (socioeconomic status, household head's education, and school grade), demographic data (gender and age), and information regarding lifestyle (physical activity, eating habits, aerobic fitness, and nutritional status) were collected. Logistic regression was used for multivariate analysis. The prevalence of abdominal obesity was 6.6% (95% confidence interval [CI]: 4.6-8.4). Being in the second (odds ratio [OR] = 0.41; 95% CI: 0.19-0.88) or third year (OR = 0.18; 95% CI: 0.06-0.59) of high school was a protective factor against abdominal obesity. In addition, students presenting low aerobic fitness (OR = 4.10; 95% CI: 1.62-10.4) and those with excess weight (OR = 208.6; 95% CI: 47.7-911.7) had a higher probability of abdominal obesity. In conclusion, demographic factors such as school grade, lifestyle habits, low aerobic fitness and excess weight are associated with central obesity.     

Genetic and environmental contributions to cannabis dependence in a national young adult twin sample

BACKGROUND: This paper examines genetic and environmental contributions to risk of cannabis dependence. METHOD: Symptoms of cannabis dependence and measures of social, family and individual risk factors were assessed in a sample of 6265 young adult male and female Australian twins born 1964-1971. RESULTS: Symptoms of cannabis dependence were common: 11.0% of sample (15.1% of men and 7.8% of women) reported two or more symptoms of dependence. Correlates of cannabis dependence included educational attainment, exposure to parental conflict, sexual abuse, major depression, social anxiety and childhood conduct disorder. However, even after control for the effects of these factors, there was evidence of significant genetic effects on risk of cannabis dependence. Standard genetic modelling indicated that 44.7% (95% CI = 15-72.2) of the variance in liability to cannabis dependence could be accounted for by genetic factors, 20.1% (95% CI = 0-43.6) could be attributed to shared environment factors and 35.3% (95% CI = 26.4-45.7) could be attributed to non-shared environmental factors. However, while there was no evidence of significant gender differences in the magnitude of genetic and environmental influences, a model which assumed both genetic and shared environmental influences on risks of cannabis dependence among men and shared environmental but no genetic influences among women provided an equally good fit to the data. CONCLUSIONS: There was consistent evidence that genetic risk factors are important determinants of risk of cannabis dependence among men. However, it remains uncertain whether there are genetic influences on liability to cannabis dependence among women.     

Relationships between physical activity, obesity and meal frequency in adolescents

OBJECTIVE: The purpose of this study was to assess the associations and impact of increased meal frequency, physical activity and 'skipping' breakfast on obesity levels in a sample of urban adolescents, aged 13-17 years old, from Porto, Portugal. METHODS: Overweight and obesity were defined according to age- and sex-specific BMI cut-points. Daily meal frequency was assessed by questionnaire. Self-reported physical activity was recalled. Results: The proportion of overweight/obese girls (p < or = 0.05) and boys (p < or = 0.001) that consumed fewer than three meals was significantly higher than those reported from normal-weight counterparts. While no statistically significant differences were reported in girls, obese boys skipped breakfast significantly more (13% vs 5.6%; p < or = 0.05) than normal-weight counterparts did. Normal-weight boys but not girls were significantly more active (p < or = 0.01) than obese peers. An additional meal in boys (OR: 2.75; p < or = 0.05) and girls (OR: 1.97; p < or = 0.05) reduced the risk of being overweight/obese. Regardless of gender, breakfast skipping is not seen as a predictor of being overweight/obese. However, boys (OR: 2.10; p < 0.003), but not girls, who were moderately active were more likely to be of normal weight. CONCLUSION: The data indicate that increased meal frequency may have a beneficial effect on a reduced BMI. Physical activity and breakfast skipping may be candidate targets for prevention programmes aimed at reducing overweight/obesity among adolescents.     

Genetic effects on alcohol dependence risk: re-evaluating the importance of psychiatric and other heritable risk factors

BACKGROUND: Genetic influences have been shown to play a major role in determining the risk of alcohol dependence (AD) in both women and men; however, little attention has been directed to identifying the major sources of genetic variation in AD risk. METHOD: Diagnostic telephone interview data from young adult Australian twin pairs born between 1964 and 1971 were analyzed. Cox regression models were fitted to interview data from a total of 2708 complete twin pairs (690 MZ female, 485 MZ male, 500 DZ female, 384 DZ male, and 649 DZ female/male pairs). Structural equation models were fitted to determine the extent of residual genetic and environmental influences on AD risk while controlling for effects of sociodemographic and psychiatric predictors on risk. RESULTS: Risk of AD was increased in males, in Roman Catholics, in those reporting a history of major depression, social anxiety problems, and conduct disorder, or (in females only) a history of suicide attempt and childhood sexual abuse; but was decreased in those reporting Baptist, Methodist, or Orthodox religion, in those who reported weekly church attendance, and in university-educated males. After allowing for the effects of sociodemographic and psychiatric predictors, 47 % (95% CI 28-55) of the residual variance in alcoholism risk was attributable to additive genetic effects, 0% (95% CI 0-14) to shared environmental factors, and 53% (95% CI 45-63) to nonshared environmental influences. CONCLUSIONS: Controlling for other risk factors, substantial residual heritability of AD was observed, suggesting that psychiatric and other risk factors play a minor role in the inheritance of AD.     

Genetic and environmental influences on pubertal timing assessed by height growth

Secular trends towards earlier puberty, possibly caused by new environmental triggers, provide a basis for periodic evaluation of the influence and interaction of genetic and environmental effects on pubertal timing. In such studies, a practical marker that reflects timing of puberty in both genders needs to be used. We investigated genetic and environmental influences on pubertal timing by using change in the relative height between early and late adolescence (HD:SDS, height difference in standard deviations) as a new marker of pubertal timing. HD:SDS correlated well with age at peak height velocity in a population of men and women with longitudinal growth data. In 2,309 twin girls and 1,828 twin boys, HD:SDS was calculated between height SDs at age 11.5 and 17.5, and 14.0 and 17.5 years, respectively. Quantitative genetic models for twin data were fitted to estimate the genetic contribution to HD:SDS. We also investigated whether the same genetic factors influenced individual differences between HD:SDS and development of secondary sex characteristics prospectively collected by pubertal development scale (PDS). Genetic effects contributed to 86 and 82% of the variance in HD:SDS in girls and boys, respectively, when using the same model including additive genetic and specific environmental factors. In girls, 30% and in boys, 49% of the genetic factors affecting PDS and HD:SDS were the same. Future comparison of the results of periodic evaluations allows estimation of possible changes in the effects of environment on timing of puberty. In such studies, HD:SDS can be used as a practical marker of pubertal timing. Am. J. Hum. Biol., 2008. © 2008 Wiley‐Liss, Inc.     

Delayed onset of pubertal development in children and adolescents with perinatally acquired HIV infection

OBJECTIVE: To examine whether greater severity of HIV infection is associated with delayed initiation of pubertal development among perinatally HIV-infected children, and to compare sexual maturation of perinatally HIV-infected children with children in the general US population using the National Health and Nutrition Examination Survey III. METHODS: In a prospective cohort study, the authors studied 983 HIV-infected children aged 6 to 18 years, who had Tanner stage assessed on at least two occasions between 1995 and 2000. Analyses were conducted separately for girls and boys to identify factors associated with onset of puberty or adrenarche (progression beyond Tanner stage 1). RESULTS: Among children who were in Tanner stage 1 at their first assessment, 185 of 413 (45%) girls and 144 of 434 (33%) boys entered puberty during the observation period. In multivariate longitudinal regression analyses adjusted for age, race/ethnicity, time interval between study visits, and other clinical factors, girls with severe immunosuppression (CD4% <15) were significantly less likely to enter adrenarche (odds ratio [OR], 0.48; 95% confidence interval [CI], 0.29-0.83) and puberty (OR, 0.57; 95% CI, 0.33-0.96) compared with girls who were not immunosuppressed (CD4% > or =25). For boys, those with severe immunosuppression were significantly less likely to enter adrenarche (OR, 0.52; 95% CI, 0.28-0.96) and tended to be less likely to begin puberty (OR, 0.69; 95% CI, 0.39-1.22) compared with boys who were not immunosuppressed. Qualitative comparisons suggested that HIV-infected children may experience delayed puberty and adrenarche compared with similarly aged children in the general US population. CONCLUSIONS: Immunosuppression was associated with delayed pubertal onset in perinatally HIV-infected children. Further studies of perinatally HIV-infected and uninfected children are needed to better quantify the delay in pubertal onset and to compare the pace of pubertal maturation.     

Risk factors for wheezing in early adolescence: a prospective birth cohort study in Brazil.

BACKGROUND: Many asthma studies are available in the literature, but few investigated whether risk factors for asthma differ by sex. OBJECTIVE: To evaluate risk factors for wheezing in early adolescence, with emphasis on sex differences. METHODS: A prospective birth cohort study was initiated in 1993; 87.5% of the original cohort was traced at 11 years, totaling 4,452 adolescents. Current wheezing was defined as at least 1 crisis in the previous 12 months. The following independent variables were analyzed: maternal smoking during pregnancy, wheezing at 4 years, maternal wheezing, and adolescent body mass index. RESULTS: Current wheezing affected 13.5% (95% confidence interval [CI], 12.4%-14.5%) of the cohort. The prevalence of current wheezing was 15.3% (95% CI, 13.7%-16.8%) in boys and 11.7% (95% CI, 10.4%-13.1%) in girls (P < .001). Maternal smoking was related to an increased risk of wheezing for boys but not for girls. There was a significant tracking of wheezing from 4 to 11 years in both sexes, although the magnitude was stronger for boys. A dose-response association between maternal wheezing and adolescent wheezing was observed in boys but not in girls. Finally, obesity was associated with an increased risk of wheezing in boys but not in girls. CONCLUSIONS: The variables explored in this investigation had a stronger effect on adolescent wheezing in boys than in girls. Public health strategies aimed at minimizing the burden of wheezing should take these sex differences into account.     

Increasing prevalence of atopic eczema in Taiwanese adolescents from 1995 to 2001

BACKGROUND: The prevalence of atopic eczema in adolescents has recently been reported as increasing in many countries, a phenomenon yet to be fully explained. This study compared the prevalence of atopic eczema among Taiwanese adolescents with individual-level risk factors and community-level data of temperature, relative humidity, and air pollutants to determine whether changes in these factors could explain the observed change in prevalence. METHODS: We conducted two nationwide, cross-sectional surveys of atopic illness and symptoms among Taiwanese 12-15-year-old schoolchildren in 1995-1996 and 2001. The effects of personal and environmental factors were assessed and temporal changes of outdoor monitoring data were also compared with the prevalence difference of atopic eczema. RESULTS: A total of 42 919 adolescents from the 1995 to 1996 survey and 10 215 adolescents from the 2001 survey attended schools located within 1 km of 22 monitoring stations. The 12-month prevalence of atopic eczema increased significantly during this period [adjusted prevalence ratio (PR)=1.43, 95% confidence interval (CI) 1.21-1.70 in boys; PR=1.77, 95% CI 1.49-2.10 in girls]. After adjustment for potential risk factors, the prevalence differences were statistically unchanged. Although parental education level contributed the most, changes in personal and environmental factors might not explain the observed prevalence increases of atopic eczema. Temporal change in the relative humidity was significantly associated with prevalence increase among boys but its contribution was also small. CONCLUSION: Correlates of the investigated risk factors that have changed over time still underlie the prevalence increases of atopic eczema in Taiwanese adolescents. The exact reasons for the rising trends remain to be elucidated.     

Higher in utero and perinatal HIV infection risk in girls than boys

OBJECTIVE: This study analyzed mother-to-child HIV transmission rates by sex and exposure time for babies born to HIV-infected, untreated African women. METHODS: Data were analyzed from 2 independent studies done in Malawi during the 1990s. Infections were established by polymerase chain reaction on blood samples. Odds ratios (ORs) for transmission were examined by period at risk: in utero (infected in umbilical cord blood), perinatal (infected in 1st postnatal blood > or =4 weeks), and postnatal (later postnatal infection). RESULTS: Among 1394 singleton births, girls were more likely to become infected than boys. For in utero transmission, the OR was 1.4 (95% CI: 0.9 to 2.2). For transmission during early life (umbilical cord blood not available) the OR was 2.7 (95% CI: 1.5 to 4.9). However, transmission risks in the perinatal and postnatal infection periods did not differ in boys and girls. Among 303 tested twin-birth pairs, girls were at higher risk than boys for in utero (OR: 2.6; 95% CI: 1.2 to 5.8) and perinatal (OR: 1.9; 95% CI: 1.0 to 3.7) infection. Recognized mother-to-child transmission risk factors did not explain the higher risk of infection in girls. CONCLUSIONS: Girls were at higher risk of early (in utero and perinatal) HIV infection than boys. It is proposed that minor histocompatibility reactions between maternal lymphocytes and infant Y chromosome-derived antigens reduce the risk of HIV transmission in boys.     

Influence of male sex and parental allergic disease on childhood wheezing: role of interactions

BACKGROUND: Boys have been reported to be more susceptible to childhood wheezing, whereas girls are more susceptible later in life. This difference might be related to both genetic and environmental factors. OBJECTIVE: To investigate the influence of male sex and parental allergic disease on the development of childhood wheezing. METHODS: Infants (n=4089) born in Stockholm were recruited in a prospective study, BAMSE. Data on parental allergic diseases were obtained from questionnaires answered at the children's birth and on symptoms of wheezing at 1, 2 and 4 years of age. Sensitization to inhalant allergens and lung function was investigated at the age of 4 years. RESULTS: Children were classified as having recurrent, transient (n=266), early-onset persistent (n=319) and late-onset wheezing (n=195). Boys were over-represented in all groups of wheezing (odds ratio, OR=1.4-1.5) and both maternal and paternal allergic disease was of importance for the wheezing outcomes. A dominating influence from maternal allergic disease was only seen in children with persistent wheezing. An interaction exceeding additivity was found between male sex and parental allergic disease, particularly in children with persistent wheezing (OR=2.9 and 95% confidence interval, CI 95% 2.1-4.0 for boys with any parental history vs. OR=1.4, CI 95% 1.0-2.1 for girls). Interaction between male sex and parental allergic disease was also observed in children who wheezed at the age of 4 years and were sensitized to inhalant allergens. CONCLUSION: Our data suggest an interaction between male sex and parental allergic disease in childhood wheezing, which may represent a sex-specific genetic influence.     

Association between overweight and early sexual maturation in Portuguese boys and girls

OBJECTIVE: The purpose of this study was to examine the relationship between sexual maturation (SM), and the prevalence of overweight among boys and girls. SUBJECTS AND METHODS: The sample of this cross-sectional study included 819 children and adolescents (382 boys and 437 girls), aged 10-15 years old randomly selected from 30 schools in the Porto region. Anthropometrical measurements (body height, weight and skinfolds thickness) were determined by standard anthropometrical methods. Body mass index (BMI) was calculated from the ratio weight/height(2) (kg/m(2)). The sum of tricipital and subscapular skinfolds (TriSub) was also used. Physicians collected data on Tanner stages during physical examination. Subjects were grouped using the quartiles of the decimal age adjusted for Tanner stages of SM and gender. RESULTS: The prevalence of overweight was higher in early maturing boys (30.5%) and early maturing girls (32.7%). The late maturers presented a lower prevalence (p < 0.05) of overweight (20.3% boys and 18.3% girls). Logistic regression analysis illustrates that early maturing is associated with an increased risk for overweight or obesity for boys (OR: 1.87 and 95% CI: 0.99-3.50) and girls (OR: 2.14 and 95% CI: 1.12-4.07), when compared with the boys and girls of the fourth quartile (p < 0.05). CONCLUSIONS: We conclude that there is an association between early SM and the prevalence of overweight in both genders.     

Causes of Stability of Aggression from Early Childhood to Adolescence: A Longitudinal Genetic Analysis in Dutch Twins

This study investigated the contribution of genetic and environmental influences on the stability of aggressive behavior from early childhood to adolescence. Two developmental models, the simplex model and the common factor model, were tested to study the underlying processes of stability and change. Measures of aggressive behavior (AGG) were obtained from maternal CBCL data as part of a large ongoing longitudinal study of the Netherlands Twin Registers (NTR) and included data from 6488 three-year-old twin pairs, 5475 seven-year-old twin pairs, 2983 ten-year-old twin pairs, and 1509 twelve-year-old twin pairs. AGG showed moderate to high stability during childhood. The stability coefficients ranged from 0.41 to 0.77 across varying intervals. Averaged across boys and girls, genetic factors accounted for approximately 65% of the total stability. Longitudinal genetic analysis indicated a simplex model for genetic effects, which suggests a dynamic development process consisting of transmission of existing genetic effects interacting with new genetic influences. This is especially true at age 7, when the influence of new genetic factors was large. Shared environmental factors accounted for approximately 25% of phenotypic stability, and it seemed that a stable set of the same shared environmental factors underlay the development of AGG. Nonshared environmental factors, when important, are age specific. Sex-specific differences for stability were identified. For boys, genetic influences were greater, whereas for girls shared environmental factors were more important. These data support the idea that both genetic and environmental influences play a role in the stability of AGG from age 3 to 12.     

Obesity risk factors in a representative group of Polish prepubertal children

Introduction

The study aim was to evaluate risk factors of obesity in Polish children aged 7 to 9 years.

Material and methods

A representative group of 2571 children (1268 girls and 1303 boys) was randomly selected according to the European Childhood Obesity Group protocol. Weight and height were measured and body mass index (BMI) was calculated. A questionnaire was completed by the children''s parents with respect to behavioural and family-related risk factors of obesity. International Obesity Task Force criteria were used for classification of children''s obesity.

Results

Obesity was found in 3.7% of girls and 3.6% of boys. There was a statistically significant association between the prevalence of obesity in girls and their mother''s obesity: OR = 5.06 (1.96–13.05), p < 0.001, father''s obesity: OR = 5.19 (1.96–13.69), p < 0.001, and both parents’ obesity: OR = 5.43 (1.39–21.29), p = 0.01. Obesity in boys was significantly associated with mother''s obesity: OR = 5.6 (2.6–12.02), p < 0.001, father''s obesity: OR = 6.21 (2.89–13.37), p < 0.001, and both parents’ obesity: OR = 7.22 (2.44–31.33), p < 0.001. Skipping or irregular eating of breakfast was a risk factor for obesity in girls with OR = 2.71 (1.33–5.51), p = 0.005. Neither family income nor parents’ education level was related to their offspring''s obesity. TV watching, physical activity level and eating in fast food places were not significant risk factors for obesity.

Conclusions

Eating breakfast regularly seems to protect girls from obesity development while low physical activity is not a significant obesity risk factor in this age group for either boys or girls. This finding stresses the more important role of healthy diet than physical activity promotion in obesity prevention in prepubertal children.     

Is obesity a risk factor for childhood asthma?

Background: In adolescents and adults, an association between obesity and asthma was found in females. Does this sex‐specific association already exist in young children? Methods: Questionnaire data on 9357 5‐ and 6‐year‐old German children were collected in 1997 in two rural regions in Bavaria. The diagnosis of asthma, hay fever, and eczema was ascertained with the ISAAC core and other validated questions. Overweight was defined by a BMI of >90th and ≤97th percentile and obesity by a BMI of >97th percentile. Results: The lifetime prevalence of doctor's diagnosed asthma in girls was 3.5% (95% CI 2.9–4.1%) for normal weight, 5.8% (95% CI 3.2–8.4%) for overweight, and 10.3% (95% CI 5.3–15.2%) for obesity, whereas no relation to weight was found in boys. Hay fever and eczema were unrelated to weight in girls and boys. The adjusted odds ratio for asthma in girls was 2.12 (95% CI 1.22–3.68) for overweight and 2.33 (95% CI 1.13–4.82) for obesity. Conclusions: A sex‐specific association with doctor's diagnosed asthma was also observed in girls at school entry. Since this association was confined to doctor's diagnosed asthma in the absence of other atopic conditions, and no association with other atopic manifestations was found, we hypothesize that this association is related to factors other than atopic sensitization.