Predictors and health effects of smoking transitions in young adults

Background: Young adults have the highest prevalence of current smoking and will have the greatest health benefits if they quit. Relatively few studies have focused specifically on this group. There is a need for high-quality data on the relationship between smoking and some factors that are either common in young adults (e.g. life-stage transitions) or known to be associated with lower cessation levels (e.g. post-cessation weight gain). Aims: To 1) examine the impact of life-stage transitions and socioeconomic position (SEP) variation across the life course on (changing) smoking status; 2) quantify weight gain after smoking cessation and the difference in weight gain between quitters and continuing smokers; 3) explore the underlying mechanisms linking smoking cessation and weight gain; and 4) investigate the longitudinal relationship between change in smoking status and change in health-related quality of life (HRQoL) in young adults. Methods: 1) For aim 1, 3 and 4, data were from the Childhood Determinants of Adult Health (CDAH) study, a 25-year follow-up of 8,498 children aged 8-15 years who participated in 1985 Australian Schools Health and Fitness Survey (ASHFS). Measurements included anthropometry, socio-demographic factors, smoking status, dietary behaviours, physical activity (PA), sedentary behaviours, and HRQoL. 2) A systematic review and meta-analysis was utilised to test the second aim. Five electronic databases were searched prior to January 2015. Population-based prospective cohort studies were included if they recorded the weight change of adult smokers from baseline (before quitting smoking) to follow-up (at least three months after cessation). Results: The main findings were that the transition into relationship with a partner and entering parenthood were associated with beneficial changes in smoking behaviours, but these influenced young men and women differently. Exposure of low SEP for greater periods of time across the life course was associated with an increased risk of smoking in mid-adulthood. Parental smoking and a self-rated low importance of not smoking at childhood appeared to be influential in mediating this relationship. In the meta-analysis using data from 35 cohort studies including 63,403 quitters and 388,432 continuing smokers, we found that people who quit smoking gained an average of 4.1 kg weight over about five years, which was 2.6 kg greater than the gain in continuing smokers. In supporting analyses from the CDAH study, this post-cessation weight gain was not attenuated after adjustment for worsening dietary and PA behaviours. Relative to continuing smoking, quitting smoking was significantly associated with an improvement in physical HRQoL. No significant association was observed between changes in smoking status and change in mental HRQoL. Conclusions: Partnering and parenting transitions and SEP trajectories across the life course predicted smoking status or changes in smoking status. Compared with continuing smoking, quitting smoking led to greater weight gain, which was not explained by changing dietary and PA behaviours, and a significant improvement in physical HRQoL. These analyses have provided novel information on predictors of smoking cessation and the associated health effects in young adults ‚Äö- a high priority group. The findings may help to promote smoking cessation and the maintenance of abstinence at the population and individual level.