The current study was conducted to evaluate the association between tobacco smoking and bladder cancer. Men (n = 281 394) and women (n = 186 134) of the National Institutes of Health-AARP (NIH-AARP) Diet and Health Study cohort completed a lifestyle questionnaire and were followed up between the years of 1995 and 2006. Previous prospective cohort studies of smoking and incident bladder cancer were identified by systematic review. Former smokers [hazard ratios (HR): 2.22; 95% CI: 2.03-2.44; number needed to harm (NNH): 1250) and current smokers (HR: 4.06; 95% CI: 3.66-4.50; NNH: 727) had higher risks of bladder cancer than never smokers. In contrast, the summary risk estimate for current smoking in seven previous studies (initiated between 1963 and 1987) was 2.94 (95% CI: 2.45-3.54). The population attributable risk (PAR) for ever smoking in this study was 0.50 (95% CI: 0.45-0.54) in men and 0.52 (95% CI: 0.45-0.59) in women. Compared with a pooled estimate of US data from cohorts initiated between 1963 and 1987, relative risks for smoking in the more recent NIH-AARP Diet and Health Study cohort were higher, with PARs for women comparable with those for men. JAMA. 2011 Aug 17;306(7):737-45. PMID: 21846855.
