Understanding the Relationship of Cigarette Smoking Trajectories Through Adolescence and Weight Status in Young Adulthood in the United States.

purposeAdolescent cigarette smoking has steadily declined since 1999, whereas adolescent obesity rates have quadrupled since the 1980s. Few studies address the longitudinal relationship of smoking and weight in youth and young adulthood. This study examines the relationship of smoking trajectories beginning in adolescence on weight status in young adulthood in a nationally representative longitudinal sample.

methodsThe study sample was drawn from the National Longitudinal Study of Adolescent to Adult Health Waves I-IV (N = 13,361). Four trajectories were generated through repeated-measures latent class analyses using current cigarette smoking status in Waves I-IV and age of initiation: nonsmokers (44%), early establishers (23%), late establishers (21%), and former smokers (12%). Wave IV weight status included self-reported body mass index (BMI) and measured waist circumference. Bivariate analyses addressed associations between smoking trajectory and BMI at each wave. Multivariate linear regression models tested the relationship of smoking trajectory and weight status at Wave IV.

resultsIn bivariate analyses, early and late establishers had a significantly lower BMI at Wave III and all smoking trajectories had a significantly lower BMI at Wave IV versus nonsmokers. All smoking trajectories had a significantly lower BMI than nonsmokers (early establishers: β = -1.27, confidence interval [CI]: -1.56 to -.98]; late establishers: β = -.84, CI: -1.16 to -.52; and former smokers: β = -.63, CI: -.93 to -.34; p < .05) in an adjusted multivariable regression model.

conclusionsThis study reveals that weight status increased over time for all trajectories; thus smoking does not mitigate obesity risk. These results have implications for both research and interventions to help youth and young adults avoid both smoking and obesity.