Smoking and subsequent risk of acute myeloid leukaemia: A pooled analysis of 9 cohort studies in Japan.

Smoking has been identified as a significant risk factor for acute myeloid leukaemia (AML). However, epidemiological evidence for the effect of smoking on the risk of AML among Asians is scarce. Here, we investigated the impact of smoking habits on the risk of AML by conducting a pooled analysis of 9 population-based prospective cohort studies in Japan. We analysed original data on smoking habits at baseline from 9 cohort studies. Hazard ratios (HRs) in the individual studies were calculated using a Cox proportional hazard model adjusted for potential confounders and combined using a random-effects model. During 4808175 person-years of follow-up for a total of 344676 participants (165567 men and 179109 women), 245 AML cases (139 men and 106 women) were identified. For both sexes combined, current smokers had a marginally significant increased risk of AML compared to never smokers (HR=1.44, 95% confidence interval [CI], 0.97-2.14). Ever smokers with more than 30 pack-years had a statistically significant increased risk of AML compared to never smokers among both sexes combined (HR=1.66, 95% CI, 1.06-2.63). By sex, this significant association was observed only among men, with an HR of 1.69 (95% CI, 1.00-2.87) for ever smokers with more than 30 pack-years relative to never smokers. In conclusion, this study confirmed that cigarette smoking increases the risk of AML in Japanese. This study provides important evidence that smoking increases the risk of AML among Asians, which has already been shown in Western populations.