Non-Daily Cigarette Smokers: Mortality Risks in the U.S.

Introduction: Worldwide, an estimated 189 million adults smoke tobacco "occasionally" but not every day. Yet few studies have examined the health risks of non-daily smoking. Methods: Data from the 1991, 1992, and 1995 U.S. National Health Interview Surveys, a nationally representative sample of 70,913 U.S. adults (aged 18-95 years) were pooled. Hazard ratios and 95% CIs for death through 2011 were estimated from Cox proportional hazards regression using age as the underlying time metric and stratified by 5-year birth cohorts in 2017. Results: Non-daily smokers reported smoking a median of 15 days and 50 cigarettes per month in contrast to daily smokers who smoked a median of 600 cigarettes per month. Compared with never smokers, lifelong nondaily smokers who had never smoked daily had a 72% higher mortality risk (95% CI=1.36, 2.18): higher risks were observed for cancer, heart disease, and respiratory disease mortalities. Higher mortality risks were observed among lifelong non-daily smokers who reported 11-30 (hazard ratio=1.34, 95% CI=0.81, 2.20); 31-60 (hazard ratio=2.02, 95% CI=1.17, 3.29); and >60 cigarettes per month (hazard ratio=1.74, 95% CI=1.12, 2.72) than never smokers. Median life-expectancy was about 5 years shorter for lifelong non-daily smokers than never smokers. As expected, daily smokers had even higher mortality risks (hazard ratio=2.50, 95% CI=2.35, 2.66) and shorter survival (10 years less). Conclusions: Although the mortality risks of non-daily smokers are lower than daily smokers, they are still substantial. Policies should be specifically directed at this growing group of smokers. Published by Elsevier Inc. on behalf of American Journal of Preventive Medicine.