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 preadolescentsʹ 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.