Teenage smoking behaviour following a high-school smoking ban in Chile: interrupted time-series analysis

OBJECTIVE To evaluate the effect of a smoking ban in high schools on smoking behaviour among Chilean students. METHODS We conducted an interrupted time-series analysis, using repeated cross-sectional data from Chile's school population survey (2000-2011) for high-school students aged 12-18 years and a control group of persons aged 19-24 years. Poisson regression models were used to assess trends in smoking behaviour before and after the policy changes. The outcome measures were self-reported smoking prevalence (any smoking in the past month) and high frequency of smoking (smoking 15 days or more per month). FINDINGS From 2005 to 2011, the prevalence of smoking declined among high-school students by 6.8% per year compared with 3.6% decline per year in the control group. The decline in the target group was 2.9% (95% confidence interval, CI: 0.18 to 5.00) greater. We estimated that 5-6 years after enforcing the law, smoking prevalence among high-school students was 13.7% lower as a result of the ban. The impact of the smoking ban was primarily driven by declines in smoking prevalence among students in grades 8 to 10. The smoking ban did not significantly alter the frequency of smoking. CONCLUSION The 2005 school smoking ban reduced smoking prevalence among younger high-school students in Chile. Further interventions targeting older individuals and frequent smokers may be needed.