[A prospective study on smoking, quitting and mortality in a cohort of elderly in Xi'an, China].

Objective: To prospective examine the relationship between smoking, quitting and mortality in older Chinese men by in Xi'an, China.

Methods: The design was a cohort analytic study. One thousand two hundred and sixty-eight retired male military veterans aged 60 or older were examined in 1987. At baseline, there were 388 never-smokers, 461 former smokers and 419 current smokers. Main outcome measure was all-cause and tobacco-associated mortality.

Results: Through 1999, 299 had died, 943 were alive and 26 lost. The mean follow-up time was 11 years and total person-year of follow-up was 14 163. After adjusting for age, blood pressure, body mass index, total cholesterol, triglycerides, alcohol intake, exercise and existing diseases, using Cox proportional hazard regression model, the relative risks (95% confidence intervals) for ever-smoking, deaths resulting from all causes, chronic obstructive pulmonary disease (COPD), lung cancer and coronary heart disease (CHD) were 1.34 (1.02 - 1.76), 3.23 (0.95 - 10.91), 2.31 (0.95 - 5.61) and 1.60 (0.81 - 3.19) respectively. The risks increased significantly with increasing amount and duration of smoking. Compared with current smokers, former smokers had lower risks of total mortality (excess risk reduction of 56%) and from CHD death (93%), but had higher risks for COPD death (excess risk increased 174%).

Conclusions: Smoking is a major cause of death in older Chinese men and quitting can save lives. These results showing that higher risks of COPD death in former smokers with or without existing diagnosed COPD at baseline than those in current smokers could be explained by either the "healthy smoker effect" or the "ill quitter effect" or both. Early recognition of the significance of COPD symptoms followed by prompt quitting should be emphasized as strategies in the control of the growing tobacco epidemic.