title: Perineal powder use and risk of endometrial cancer in postmenopausal women.
abstract: BACKGROUND
  Most known endometrial cancer risk factors involve genetics or exposure to unopposed estrogens; less is known about risk due to environmental exposures. While several studies have found an increased risk of ovarian cancer associated with perineal powder use, only two studies have addressed perineal powder use and endometrial cancer risk.
  
  
  METHODS
  We used Cox proportional hazards regression to examine the association between perineal powder use and endometrial cancer risk using the Women's Health Initiative Observational Study Research Materials obtained from the National Heart, Lung, and Blood Institute Biological Specimen and Data Repository Coordinating Center.
  
  
  RESULTS
  Of the 48,526 women in our primary analysis, 25,181 (52 %) reported ever use of perineal powder. During 364,134 person-years of follow-up, 447 participants were diagnosed with endometrial cancer. Ever use of perineal powder was not associated with increased risk of endometrial cancer (multivariable-adjusted hazard ratio, 1.06; 95 % confidence interval, 0.87-1.28). External use of powder on the genitals and/or on sanitary napkins was also not significantly associated with risk of endometrial cancer. However, use of powder on a diaphragm for twenty or more years was associated with a threefold increase in risk of endometrial cancer compared to women who never used perineal powder (multivariable-adjusted hazard ratio, 3.06; 95 % CI, 2.00-4.70).
  
  
  CONCLUSIONS
  Any duration of external use of perineal powder was not associated with increased risk of endometrial cancer; however, long-term use of powder on a diaphragm may increase the risk of endometrial cancer.
authors.affiliation: Division of Biostatistics and Epidemiology, Department of Public Health, School of Public Health and Health Sciences, University of Massachusetts Amherst, 715 North Pleasant Street, Amherst, MA 01003-9304, USA. lbcrawfo@acad.umass.edu
authors.forename: Lori
authors.initials: L
authors.lastname: Crawford
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Reeves
authors.forename: Nicole
authors.initials: N
authors.lastname: Luisi
authors.forename: Raji
authors.initials: R
authors.lastname: Balasubramanian
authors.forename: Susan R
authors.initials: SR
authors.lastname: Sturgeon
mesh_terms: D000368:Aged; D015992:Body Mass Index; D016889:Endometrial Neoplasms / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D012307:Risk Factors; D013627:Talc; D016387:Women's Health
chemical_list: D013627:Talc