title: Menstrual and reproductive factors and fracture risk: the Leisure World Cohort Study.
abstract: BACKGROUND
  Because menopausal estrogen is related to the development of osteoporosis, we investigated the potential associations of the estrogen-related events of menarche, pregnancy, and menopause with fracture risk in a population-based, prospective study of older women.
  
  
  METHODS
  The Leisure World Cohort was established in the early 1980s when residents of a California retirement community, including 8877 women, completed a health survey. Incident fractures of the hip (n = 1220), wrist (n = 463), and spine (n = 613) incurred over two decades were identified from four follow-up questionnaires, hospital discharge records, and (for hip fracture) death certificates. Hazard ratios (HR) adjusted for age and other potential confounders were calculated using proportional hazards regression.
  
  
  RESULTS
  Late age at menarche was associated with decreased hip fracture risk (HR = 0.84, 95% CI 0.72-0.98, for age > or = 14 vs. < or = 12 years) but was unrelated to fractures at other sites. Hip fracture risk was also reduced in women who had been pregnant (HR = 0.83, 95% CI 0.72- 0.95). Women who reported menopause at age 45+ had a lower risk of wrist fracture compared with those with menopause at age < or = 44 (HR = 0.74, 95% CI 0.58-0.95 for ages 45-54; HR = 0.71, 95% CI 0.49-1.04 for ages 55+). Although fracture risks did not differ between ever and never users of menopausal estrogen, recency since last use was related to wrist fractures (HR = 1.09, 95% CI 1.03-1.16 for each 5 years since last years).
  
  
  CONCLUSIONS
  The estrogen-related events of menarche, pregnancy, and menopause were not associated with osteoporotic fracture risk in a consistent manner. Other factors related to these events may be influencing development of osteoporosis and the likelihood of sustaining a fracture in older women.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA. annliahi@usc.edu
authors.forename: Annlia
authors.initials: A
authors.lastname: Paganini-Hill
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Atchison
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Gornbein
authors.forename: Aurelia
authors.initials: A
authors.lastname: Nattiv
authors.forename: Susan K
authors.initials: SK
authors.lastname: Service
authors.forename: Stuart C
authors.initials: SC
authors.lastname: White
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D002140:California / Q000453:epidemiology; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology*; D006304:Health Status; D006620:Hip Fractures / Q000453:epidemiology; D006801:Humans; D008572:Menarche; D016017:Odds Ratio; D017584:Reproductive History; D012307:Risk Factors; D016103:Spinal Fractures / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014954:Wrist Injuries / Q000453:epidemiology