title: Self-reported sleep and nap habits and risk of mortality in a large cohort of older women.
abstract: OBJECTIVE
  To determine the association between self-reported sleep and nap habits and mortality in a large cohort of older women.
  
  
  METHODS
  Study of Osteoporotic Fractures prospective cohort study.
  
  
  METHODS
  Four communities within the United States.
  
  
  METHODS
  Eight thousand one hundred one Caucasian women aged 69 and older (mean age 77.0).
  
  
  METHODS
  Sleep and nap habits were assessed using a questionnaire at the fourth clinic visit (1993/94). Deaths during 7 years of follow-up were confirmed with death certificates. Underlying cause of death was assigned according to the International Classification of Diseases, Ninth Revision, Clinical Modification.
  
  
  RESULTS
  In multivariate models, women who reported napping daily were 44% more likely to die from any cause (95% confidence interval (CI)=1.23-1.67), 58% more likely to die from cardiovascular causes (95% CI=1.25-2.00), and 59% more likely to die from noncardiovascular noncancer causes (95% CI=1.24-2.03) than women who did not nap daily. This relationship remained significant in relatively healthy women (those who reported no comorbidities). Women who slept 9 to 10 hours per 24 hours were at greater risk of death from cardiovascular and other (noncardiovascular, noncancer) causes than those who reported sleeping 8 to 9 hours.
  
  
  CONCLUSIONS
  Older women who reported napping daily or sleeping at least 9 hours per 24 hours are at greater risk of death from all causes except cancer. Future research could determine whether specific sleep disorders contribute to these relationships.
authors.affiliation: Research Institute, California Pacific Medical Center, San Francisco, California 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: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Ensrud
authors.forename: Susan
authors.initials: S
authors.lastname: Redline
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: D000368:Aged; D002423:Cause of Death; D016009:Chi-Square Distribution; D005260:Female; D006184:Habits; D006801:Humans; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000401:mortality*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D044465:White People