Early health effects of the emerging tobacco epidemic in China. A 16-year prospective study.
Chen ZM., Xu Z., Collins R., Li WX., Peto R.
CONTEXT: In recent decades, there has been a rapid and substantial increase in tobacco consumption in China, particularly by men, but little is known from local epidemiologic studies about the pattern of smoking-related deaths. OBJECTIVE: To assess the current health effects of cigarette smoking in Shanghai, China. DESIGN: Prospective observational study of mortality in relation to cigarette smoking. SETTING: Eleven factories in urban Shanghai. SUBJECTS: A total of 9351 adults (6494 men and 2857 women) aged 35 to 64 years at baseline survey during the 1970s. OUTCOME MEASURES: All-cause and cause-specific mortality. RESULTS: During an average follow-up of 16 years, 881 men and 207 women died. Among men, 61% had described themselves as current cigarette smokers at baseline, and their overall mortality was significantly greater than that of nonsmokers (relative risk [RR], 1.4; 95% confidence interval [CI], 1.2-1.7; P<.001). The excess was almost twice as great (RR, 1.8; 95% CI, 1.5-2.2 [corrected]; P<.001) among the men who had begun smoking before the age of 25 years and was significantly associated with the number of cigarettes smoked (P<.001 for trend) after adjustment for other major risk factors. The chief sources of the excess were lung cancer (RR, 3.8; 95% CI, 2.1-6.8; P<.001), esophageal cancer (RR, 3.6; 95% CI, 1.2-10.5; P=.02), liver cancer (RR, 2.0; 95% CI, 1.1-3.7; P=.03), coronary heart disease (RR, 1.8; 95% CI, 1.0-3.2; P=.04), and chronic obstructive pulmonary disease (RR, 2.5; 95% CI, 1.4-4.4; P<.01). Among the men in this Chinese population, about 20% (95% CI, 12%-29%) of all deaths during the study period could be attributed to cigarette smoking. Of these deaths, one third involved lung cancer, one third involved other cancers, and one third involved other diseases. Only 7% of women described themselves as current cigarette smokers at baseline, but among them there was also a statistically significant excess of overall mortality (RR, 1.7; 95% CI, 1.2-2.5; P<.01). CONCLUSIONS: Cigarette smoking is already a major cause of death in China, and among middle-aged Shanghai men, about 20% of all deaths during the 1980s were due to smoking. The excess was greatest among men who began smoking before the age of 25 years, about 47% of whom would, at 1987 mortality rates, die between the ages of 35 and 69 years (compared with only 29% of nonsmokers). These estimates reflect the consequences of past smoking patterns. The future health effects of current smoking patterns are likely to be greater because of the recent large increase in cigarette consumption, particularly at younger ages, in China.