Trajectories of weight disturbances during adolescence in relation to gender in a Swedish cohort.

AIM: To explore developmental trajectories among adolescents of thinness and overweight in relation to gender. METHODS: A group-based procedure was used to determine patterns of weight disturbances in a school-based sample of 3020 Swedish adolescents followed from age 11 to 18. A sensitivity analysis was performed to compensate for an increasing number of missing height and weight data after grade 8. RESULTS: Six trajectories represented the best description of developmental weight disturbances with the exception of thinness among boys, which was best described by four trajectories. Concerning thinness, 5.9% of girls and 4.2% of boys developed this condition during the study period, while 1.9% of girls and 3.0% of boys recovered from their initial thinness. For overweight, (including obesity) 1.5% of girls and 3.1% of boys developed this weight disturbance during the study period, while 10.1% of girls and 9.3% of boys recovered from overweight/obesity. Non-reporting of height and weight was biased towards an underestimation of the true prevalence of overweight and obesity in girls and of thinness in boys. CONCLUSIONS: Developmental trajectories provide a novel method to describe the dynamics of weight disturbances during adolescence. Similar patterns were found for overweight and thinness in boys and girls but group sizes varied between genders. Non-reporting of height and weight was found in a gender-specific pattern.

Low physical activity is a predictor of thinness and low self-rated health: gender differences in a Swedish cohort.

PURPOSE: To examine the relationship between leisure time physical activity in 15-year-old students, and weight status and self-rated health 3 years later. METHODS: Data were used from two follow-up waves, one in 2002 (grade 9, age 15 years) and one in 2005 (grade 12, age 18 years) of a cohort of approximately 2,500 adolescents. Adolescents reported height and weight, health behaviors, and self-rated health by a questionnaire at both occasions. Age and gender-specific body mass index cut-off points for thinness, overweight, and obesity were used to assess weight status. Logistic regression analyses were performed with weight status and self-rated health as the outcomes and level of leisure time physical activity as the independent variable. Adjustments were made for parental years of education, student's current smoking habits, and baseline body mass index. RESULTS: As compared with students who were active for more than 4 hours per week during leisure time, being active 2-4 hours (odds ratio [OR]: 4.15, confidence interval [CI]: 1.62-10.60) and <2 hours (OR: 3.92, CI: 1.30-11.78) predicted thinness in boys. In girls, the risk was smaller and became significant at <2 hours per week (OR: 2.57, CI: 1.38-4.77). Overweight or obesity was not significantly predicted by physical activity. A significant risk of low self-rated health was found at follow-up in boys active for <4 hours per week compared with those active for >4 hours per week. CONCLUSION: Physical activity is important to maintain a healthy body weight and for future self-rated health in boys.

Trajectories of smokeless tobacco use and of cigarette smoking in a cohort of Swedish adolescents: differences and implications.

Developmental trajectories of cigarette smoking have often been described, but there are no such analyses dealing with smokeless tobacco use. A semi-parametric group-based mixture modeling procedure was used to determine the development of smokeless tobacco (snus) use, as well as of cigarette smoking, over time in a cohort of 2,175 Swedish adolescents who were never-users of tobacco at the time of recruitment. An indicator of snus and of cigarette consumption in the previous year was used to model the development of the behavior between 11 and 18 years of age. For snus use three trajectories best described the cohort's experience, while four trajectories provided the best description of cigarette smoking in the cohort. For both tobacco types there were two escalation patterns and one sustained trial trajectory, while an extinction pattern was apparent for cigarette smoking only. Marked sex differences were found, since rapid escalation for snus use was found only among males while high consumption of cigarettes was observed only among females. Dual users (54.9% of all users) showed a trajectory of steeper and more prolonged increase of tobacco consumption than exclusive users of either snus or cigarettes. Several risk factors for tobacco use measured at baseline influenced individual probabilities of belonging to a particular trajectory. The developmental patterns of snus use and cigarette smoking showed high similarity, but they evolved differently in the two sexes. Dual users emerged as a high-risk group for tobacco dependence and tobacco-related harms.

Knowledge about tobacco and subsequent use of cigarettes and smokeless tobacco among Swedish adolescents.

PURPOSE: To investigate whether knowledge of the risks and properties of tobacco among adolescents influences their future use of cigarettes and smokeless tobacco in different directions. METHODS: A prospective cohort study of 2581 adolescents whose knowledge of tobacco was assessed in the sixth grade by means of a multi-item scale. Tobacco use was assessed by annual surveys up to the ninth grade. RESULTS: Knowledge level was not associated with future use. Items dealing with addictive properties of nicotine were prospectively associated with smokeless tobacco ("snus") use only. CONCLUSIONS: A high level of knowledge of the risks associated with tobacco is not a predictor of future nonuse or of a shift to smokeless tobacco rather than cigarettes. Attitudes and expectations may determine knowledge rather than vice versa.

School and class environments are differently linked to future smoking among preadolescents.

BACKGROUND: There are few observational studies of school and class risk factors for smoking behavior in preadolescence. METHODS: A cohort study of 2,883 children recruited in the fifth grade with follow-up in sixth grade was undertaken. Information on school and class factors was collected from principals and teachers of 91 schools. RESULTS: A decreased risk of smoking uptake was associated with exposure to short antitobacco education prior to the fifth grade (compared to no education). Problematic interpersonal relations in the class were associated with a relative risk of smoking initiation of 1.42 (confidence interval 1.05, 1.93) compared to positive interpersonal relations. This excess risk was not mediated by class smoking prevalence in the fifth grade. School policy and school characteristics were not significantly associated with preadolescents' smoking. CONCLUSIONS: Class-related, rather than school-related, characteristics were associated with smoking initiation and progression. Changes in microenvironmental factors might be useful in smoking prevention among preadolescents.