Reduction in total and major cause-specific mortality from tobacco smoking cessation: a pooled analysis of 16 population-based cohort studies in Asia.

Abstract

BACKGROUND\nLittle is known about the time course of mortality reduction following smoking cessation in Asians who have smoking behaviours distinct from their Western counterparts. We evaluated the level of reduction in all-cause, cardiovascular disease (CVD) and lung cancer mortality by years since quitting smoking, in Asia.\n\n\nMETHODS\nUsing Cox regression, we analysed individual participant data (n\u2009=\u2009709\u2009151) from 16 prospective cohorts conducted in China, Japan, Korea/Singapore, and India/Bangladesh, separately by cohorts. Cohort-specific hazard ratios (HRs) were combined using a random-effects meta-analysis.\n\n\nRESULTS\nDuring a mean follow-up of 12.0\u2009years, 108\u2009287 deaths were ascertained-35\u2009658 from CVD and 7546 from lung cancer. Among Asian men, a dose-response relationship of risk reduction in deaths from all causes, CVD and lung cancer was observed with an increase in years after smoking cessation. Compared with never smokers, however, all-cause and CVD mortality among former smokers remained elevated 10-14\u2009years after quitting [multivariable-adjusted HR (95% confidence interval (CI) = 1.25 (1.13-1.37) and 1.20 (1.02-1.41), respectively]. Lung cancer mortality stayed almost 2-fold higher than among never smokers 15-19\u2009years after smoking cessation [1.97 (1.41-2.73)], particularly among former heavy smokers [2.62 (1.71-4.00)]. Women who quitted for ≥5\u2009years retained a significantly elevated mortality from all causes, CVD and lung cancer. Overall patterns of the cessation-mortality associations were similar across countries.\n\n\nCONCLUSIONS\nOur findings suggest that adverse effects of tobacco smoking persist for an extended time period, even for more than two decades, which is beyond the time windows defined in current clinical guidelines for risk assessment of lung cancer and CVD.