title: Association between smoking and risk of bladder cancer among men and women.
abstract: BACKGROUND
  Previous studies indicate that the population attributable risk (PAR) of bladder cancer for tobacco smoking is 50% to 65% in men and 20% to 30% in women and that current cigarette smoking triples bladder cancer risk relative to never smoking. During the last 30 years, incidence rates have remained stable in the United States in men (123.8 per 100,000 person-years to 142.2 per 100,000 person-years) and women (32.5 per 100,000 person-years to 33.2 per 100,000 person-years); however, changing smoking prevalence and cigarette composition warrant revisiting risk estimates for smoking and bladder cancer.
  
  
  OBJECTIVE
  To evaluate the association between tobacco smoking and bladder cancer.
  
  
  METHODS
  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 October 25, 1995, and December 31, 2006. Previous prospective cohort studies of smoking and incident bladder cancer were identified by systematic review and relative risks were estimated from fixed-effects models with heterogeneity assessed by the I(2) statistic.
  
  
  METHODS
  Hazard ratios (HRs), PARs, and number needed to harm (NNH).
  
  
  RESULTS
  During 4,518,941 person-years of follow-up, incident bladder cancer occurred in 3896 men (144.0 per 100,000 person-years) and 627 women (34.5 per 100,000 person-years). Former smokers (119.8 per 100,000 person-years; HR, 2.22; 95% confidence interval [CI], 2.03-2.44; NNH, 1250) and current smokers (177.3 per 100,000 person-years; HR, 4.06; 95% CI, 3.66-4.50; NNH, 727) had higher risks of bladder cancer than never smokers (39.8 per 100,000 person-years). In contrast, the summary risk estimate for current smoking in 7 previous studies (initiated between 1963 and 1987) was 2.94 (95% CI, 2.45-3.54; I(2) = 0.0%). The PAR for ever smoking in our study was 0.50 (95% CI, 0.45-0.54) in men and 0.52 (95% CI, 0.45-0.59) in women.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, 6120 Executive Blvd, EPS/320, MSC 7232, Rockville, MD 20852, USA. freedmanne@mail.nih.gov
authors.forename: Neal D
authors.initials: ND
authors.lastname: Freedman
authors.forename: Debra T
authors.initials: DT
authors.lastname: Silverman
authors.forename: Albert R
authors.initials: AR
authors.lastname: Hollenbeck
authors.forename: Arthur
authors.initials: A
authors.lastname: Schatzkin
authors.forename: Christian C
authors.initials: CC
authors.lastname: Abnet
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012306:Risk; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D001749:Urinary Bladder Neoplasms / Q000453:epidemiology*