LAUSR

OBJECTIVE we aimed to investigate the association of smoking cessation with risk of all-cause mortality amongst oldest old people (aged ≥ 80 years). DESIGN this was a prospective cohort study. SETTING the Chinese Longitudinal Healthy Longevity Survey, implemented in 23 provinces of China. PARTICIPANTS a total of 28,643 community-dwelling oldest old people (mean age, 92.9 ± 7.5 years) were included. METHODS in this community-based cohort study, Cox proportional hazards models were used to examine the association of smoking cessation with risk of all-cause mortality. RESULTS during 136,585 person-years of follow-up from baseline to 1 September 2014, compared with never smokers, hazard ratios and 95% confidence intervals for all-cause mortality were 1.06 (1.02-1.10) for current smokers, 1.23 (1.09-1.39) for transient quitters (≤1 consecutive years since smoking cessation), 1.22 (1.12-1.32) for recent quitters (2-6 consecutive years since smoking cessation) and 1.11 (1.02-1.22) for long-term quitters (>6 consecutive years since smoking cessation). Cox models with penalised splines revealed an increased risk of all-cause mortality after smoking cessation; the highest mortality risk was observed within 2-4 years after smoking cessation and the risk gradually decreased with duration of smoking cessation. We further conducted subgroup analyses and sensitivity analyses to reduce the impact of reverse causation. CONCLUSIONS smoking is harmful to health in all populations. Our study findings indicated smoking cessation in late life to be associated with increased risk of all-cause mortality amongst oldest old people who have smoked for a long time.