title: Self-reported sleep and nap habits and risk of falls and fractures in older women: the study of osteoporotic fractures.
abstract: OBJECTIVE
  To test the association between self-reported sleep and nap habits and risk of falls and fractures in a large cohort of older women.
  
  
  METHODS
  Study of Osteoporotic Fractures prospective cohort study.
  
  
  METHODS
  Clinical centers in Baltimore, Maryland; Minneapolis, Minnesota; Portland, Oregon; and the Monongahela Valley, near Pittsburgh, Pennsylvania.
  
  
  METHODS
  Eight thousand one hundred one community-dwelling Caucasian women aged 69 and older (mean 77.0).
  
  
  METHODS
  Sleep and nap habits were assessed using a questionnaire at the fourth clinic visit (1993/94). Fall frequency during the subsequent year was ascertained using tri-annual questionnaire. Incident hip and nonspinal fractures during 6 years of follow-up were confirmed using radiographic reports.
  
  
  RESULTS
  Five hundred fifty-three women suffered hip fractures, and 1,938 suffered nonspinal fractures. In multivariate models, women who reported napping daily had significantly higher odds of suffering two or more falls during the subsequent year (odds ratio=1.32, 95% confidence interval (CI)=1.03-1.69) and were more likely to suffer a hip fracture (hazard ratio (HR)=1.33, 95% CI=0.99-1.78) than women who did not nap daily. Those sleeping at least 10 hours per 24 hours had a higher risk of nonspinal fracture than (HR=1.26, 95% CI=1.00-1.58) and a similar but nonsignificant increased risk of hip fracture to (HR=1.43, 95% CI=0.95-2.15) those who reported sleeping between 8 and 9 hours.
  
  
  CONCLUSIONS
  Self-reported long sleep and daily napping are associated with greater risk of falls and fractures in older women. Interventions to improve sleep may reduce their risk of falls and fractures. Future research is needed to determine whether specific sleep disorders contribute to these relationships.
authors.affiliation: Research Institute, California Pacific Medical Center, San Francisco, 94107, USA. kstone@sfcc-cpmc.net
authors.forename: Katie L
authors.initials: KL
authors.lastname: Stone
authors.forename: Susan K
authors.initials: SK
authors.lastname: Ewing
authors.forename: Li-Yung
authors.initials: LY
authors.lastname: Lui
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Ensrud
authors.forename: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Bauer
authors.forename: Jane A
authors.initials: JA
authors.lastname: Cauley
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Hillier
authors.forename: Steven R
authors.initials: SR
authors.lastname: Cummings
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data*; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D050723:Fractures, Bone / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D015994:Incidence; D016017:Odds Ratio; D010024:Osteoporosis / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology*; D011446:Prospective Studies; D012146:Rest / Q000502:physiology*; D012307:Risk Factors; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology