Tobacco smoking and risks of >470 diseases in China: a prospective cohort study

BACKGROUND: Tobacco smoking is estimated to account for >1 million annual deaths in China, and the epidemic continues to increase in men. Large nationwide prospective studies linked to different health records can help assess periodically disease burden attributed to smoking. We examined associations of smoking with an extensive range of disease incidence and mortality in China. METHODS: The prospective China Kadoorie Biobank recruited >512,000 adults aged 30-79 years from 10 diverse areas during 2004-2008, and recorded detailed smoking information. During 12-year follow-up, 1,137,603 ICD-10 coded hospitalisation events and 48,760 deaths were recorded, involving 476 and 85 distinct conditions, each with ≥100 incident cases and deaths, respectively. Cox regression yielded adjusted hazard ratios (HRs) associating smoking with disease outcomes, adjusting for multiple-testing. FINDINGS: At baseline 67·7% of men and 3·2% of women (overall 29·4%) ever smoked regularly. Compared with never-smokers, ever-smokers had significantly higher risks for 9 of 18 ICD-10 disease chapters examined at ages 35-84 years. For individual conditions, smokers had significantly higher risks of 56 diseases (men 50; women 24) and 22 causes of death (men 17; women 9). Among men, ever-smokers had HR of 1·09 (95% CI 1·08-1·11) for any disease incidence, and also significantly more episodes and longer duration of hospitalisation, particularly those due to cancer and respiratory diseases. For overall mortality, the HRs were greater in urban than in rural men (1·50 [1·43-1·58] vs. 1·25 [1·20-1·30]). Among urban men who began smoking at age <18 years, the HRs were 2·06 (1·89-2·24) for overall mortality and 1·32 (1·27-1·37) for any disease incidence. In this population, 20% of male (urban 24%; rural 16%) and 3% of female deaths were attributed to ever-regular smoking. INTERPRETATION: Among Chinese adults, smoking was associated with higher risks of morbidity and mortality from a wide range of diseases. Among men, the future smoking-attributed disease burden will increase further, highlighting a pressing need for reducing consumption, through widespread cessation and uptake prevention.