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Purpose: To evaluate the associations between family socioeconomic trajectories from 0 to 11 years of age and risk factors for noncommunicable disease at 15 years., Methods: Individuals born in the city of Pelotas, Brazil, in 1993 are part of a birth cohort study. Socioeconomic position, collected at birth and at 11 years of age, was our main exposure. Risk factors for chronic disease were collected at 15 years. Body mass index was transformed into Z score using the World Health Organization standard. Transport and leisure-time physical activity, smoking, and alcohol consumption were assessed by self-report. Blood pressure was measured using a digital sphygmomanometer., Results: Of 5,249 cohort members, 85.7% were located at the 15-year follow-up visit. Rich adolescents were more likely to be overweight, be obese, and not use active modes of transport to school. Poor adolescents were more likely to smoke. In relation to socioeconomic trajectories, the odds of obesity were 46% higher among those who were "always rich" compared with those who were "always poor"; the odds of use of an inactive mode of transportation were 326% greater among the "always rich" than the "always poor," whereas the reverse was observed for smoking (odds of 200%). The "always rich" had one-half the odds of walking or cycling to school compared with those who became wealthy in the studied period., Conclusions: Adolescent socioeconomic position is a stronger determinant of risk factors for noncommunicable diseases than socioeconomic trajectories. However, trajectories do matter, particularly in terms of use of active transportation to school., (Copyright © 2012 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the prospective association between leisure-time physical activity practice at 11 years of age and incidence of school failure from 11 to 15 years of age., Methods: The sample comprised >4,300 adolescents followed up from birth to 15 years of age participating in a birth cohort study in Pelotas, Brazil. The incidence of school failure from age 11 to 15 years was calculated by first excluding from the analyses all subjects who experienced a school failure before 11 years of age, and then categorizing as "positive" all those who reported repeating a grade at school from 11 to 15 years of age. Leisure-time physical activity was measured using a validated questionnaire., Results: The incidence of school failure was 47.9% among boys and 38.2% among girls. Adolescents in the top quartile of leisure-time physical activity practice at 11 years of age had a higher likelihood of school failure (OR: 1.36; 95% CI: 1.06, 1.75) compared with the least active adolescents. In adjusted analyses stratified by sex, boys in the top quartile of leisure-time physical activity practice at 11 years of age were also more likely to have failed at school from age 11 to 15 years (OR: 1.60; 95% CI: 1.09, 2.33)., Conclusions: Adolescents allocating >1,000 min/wk to leisure-time physical activity were more likely to experience a school failure from 11 to 15 years of age. Although this finding does not advocate against physical activity promotion, it indicates that excess time allocated to physical activity may jeopardize school performance among adolescents., (Copyright © 2012 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the effect of obesity at the start of adolescence on the prevalence, incidence and maintenance of chest wheezing among individuals aged 11-15 years in a birth cohort in a developing country., Methods: The seventh follow-up of the 1993 Pelotas birth cohort occurred in 2004 (individuals aged 10-11 years). Between January and August 2008, the eighth follow-up of the cohort was conducted. All the individuals of the original cohort who were alive (who were then adolescents aged between 14 and 15 years) were targets for the study. The International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire was used to define wheezing. In addition to the body mass index (BMI), used to define obesity by the World Health Organization (WHO) criteria, we assessed skinfold thickness., Results: From the original cohort, 4,349 individuals were located (85.7% follow-up rate). The prevalence of chest wheezing at 11 and 15 years were 13.5% (95% CI: 12.5%-14.5%) and 12.1% (95% CI: 11.1%-13.1%), respectively. The prevalence of wheezing at both times was 4.5% (95% CI: 3.9%-5.1%) and the incidence of wheezing was 7.5% (95% CI: 6.7%-8.3%). Independent of the effect of various confounding variables, the prevalence of wheezing at 15 years was 50% greater among obese individuals than among eutrophic individuals at 11 years (RR 1.53; 95% CI: 1.14-2.05). The greater the skinfold tertile at 11 years, the higher the prevalence of wheezing at 15 years was (p = .011). Weight status and skinfolds did not present any association with incident wheezing. After controlling for confounding factors, the risk of persistent wheezing among obese individuals at 11 years was 1.82 (95% CI: 1.30-2.54)., Conclusions: Since obesity at the start of adolescence is associated with asthma symptom persistence, prevention and treatment of obesity may reduce avoidable healthcare costs and disease burden., (Copyright © 2012 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.)

Purpose: We explored predictors of nutritional status change from 11 to 15 years of age by analyzing prospective data., Methods: We collected data at 11 and 15 years of age from individuals born in 1993 in Pelotas, Brazil. We assessed nutritional status using body mass index (BMI) for age in z-score according to the World Health Organization 2007 standards. Independent variables collected at 11 years of age were socioeconomic position, adolescent's perception of own weight, body dissatisfaction, and weight loss dieting., Results: Of the 4,032 adolescents whose nutritional status could be evaluated in the two follow-ups, 93% maintained their nutritional status classification from 11 to 15 years. A total of 102 (2.8%) became obese and 181 (4.5%) ceased to be obese in the 4-year period. The prevalence of obesity decreased from 11 to 15 years of age in both boys and girls. Low-income girls were more likely to become obese from 11 to 15 years of age compared with high-income ones. Among boys, those with high income were more likely to cease being obese compared those with low income. Those who perceived themselves to be obese, who wished to have a smaller silhouette, and who were on diets to lose weight were more likely to become obese or to achieve a normal BMI category at 15 years of age., Conclusions: BMI tracks strongly in early adolescence. This finding suggests that interventions to more effectively change nutritional status should be implemented in childhood and should consider emotional aspects as well as social and biological ones., (Copyright © 2012. Published by Elsevier Inc.)

Purpose: To evaluate the prevalence of tobacco use, and factors associated with it, in early adolescent (aged 10-12 years) participants of the 1993 Pelotas (Brazil) Birth Cohort Study., Methods: Children born in 1993 in Pelotas, Brazil were included in a prospective health study. In 2004-2005, all cohort members were sought. Adolescents and mothers were interviewed. A confidential questionnaire was applied to adolescents, including a section on smoking. Smoking experience was defined as having tried at least one cigarette in life., Results: Follow-up rate was 87.5%; 4452 adolescents were interviewed. Mean age was 11.3 years. Only 58 adolescents did not answer the question on smoking experience. Out of the 4394 respondents, 162 (3.7%; 95% confidence interval [CI] 3.1-4.2) had tried smoking. Of these, approximately half smoked the first cigarette before 10 years of age. Seventy-three cohort members reported smoking daily. In multivariable analysis, variables positively associated with smoking experience were: male gender, maternal smoking during pregnancy, living without the biological father, poor relationship with the mother, being beaten by the parents, family conflict, maternal smoking in 2004-2005, bad influences on the adolescent, participation in fights, history of attempting to run away from home, and experience with alcoholic beverages. The association was negative for socioeconomic level., Conclusion: Family-related variables and habits of the adolescent were strongly associated with smoking in early adolescence. Because experimentation with tobacco in adolescence is related to a marked increase in the risk of tobacco addiction in adulthood, early interventions are warranted.