New Study Links Smoking to Higher Bladder Cancer Risk

Population attributable risks same for men and women; risks higher in former, current smokers

WEDNESDAY, Aug. 17 (HealthDay News) -- The relative risk for bladder cancer from tobacco smoking is higher than reported in previous studies, with population attributable risks (PARs) for women comparable to those for men, according to a study published Aug. 17 in the Journal of the American Medical Association.

Neal D. Freedman, Ph.D., M.P.H., from the National Institutes of Health (NIH) in Rockville, Md., and colleagues investigated the association between tobacco smoking and bladder cancer in 281,394 men and 186,134 women from the NIH-American Association of Retired Persons (AARP) Diet and Health Study cohort who completed a lifestyle questionnaire and were followed up between October 1995 and December 2006. A systematic review identified previous studies of smoking and incident bladder cancer. Relative risks were estimated from fixed-effects models. Heterogeneity was assessed by the I² statistic. Outcome measures included hazard ratios (HRs), PARs, and number needed to harm (NNH).

The investigators found incident bladder cancer in 3,896 men (144.0 per 100,000 person-years) and 627 women (34.5 per 100,000 person-years) during 4,518,941 person-years of follow-up. The risk of bladder cancer was higher in former (119.8 per 100,000 person-years; HR, 2.22; NNH, 1,250) and current smokers (177.3 per 100,000 person-years; HR, 4.06; NNH, 227) than in never smokers (39.8 per 100,000 person-years). The summary risk estimate for current smoking in seven previous studies between 1963 and 1987 was 2.94 (I² = 0.0 percent). The PAR for ever smoking was 0.50 in men and 0.52 in women.

"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," the authors write.

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