title: Exploring the effect of depression on physical disability: longitudinal evidence from the established populations for epidemiologic studies of the elderly.
abstract: OBJECTIVE
  This study examined the effect of depression on the incidence of physical disability and the role of confounding and explanatory variables in this relationship.
  
  
  METHODS
  A cohort of 6247 subjects 65 years and older who were initially free of disability was followed up for 6 years. Baseline depression was assessed by the Center for Epidemiological Studies Depression Scale. Disability in mobility and disability in activities of daily living were measured annually.
  
  
  RESULTS
  Compared with the 5751 nondepressed subjects, the 496 depressed subjects had a relative risk (95% confidence interval) of 1.67 (1.44, 1.95) and 1.73 (1.54, 1.94) for incident disability in activities of daily living and mobility, respectively. Adjustment for sociodemographic characteristics and baseline chronic conditions reduced the risks to 1.39 (1.18, 1.63) and 1.45 (1.29, 1.93), respectively. Less physical activity and fewer social contacts among depressed persons further explained part of their increased disability risk.
  
  
  CONCLUSIONS
  Depression in older persons may increase the risk for incident disability. This excess risk is partly explained by depressed persons' decreased physical activity and social interaction. The role of other factors (e.g., biological mechanisms) should be examined.
authors.affiliation: Epidemiology, Demography, and Biometry Program, National Institute on Aging, Bethesda, MD 20892, USA.
authors.forename: B W
authors.initials: BW
authors.lastname: Penninx
authors.forename: S
authors.initials: S
authors.lastname: Leveille
authors.forename: L
authors.initials: L
authors.lastname: Ferrucci
authors.forename: J T
authors.initials: JT
authors.lastname: van Eijk
authors.forename: J M
authors.initials: JM
authors.lastname: Guralnik
mesh_terms: D000203:Activities of Daily Living; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001900:Boston / Q000453:epidemiology; D015897:Comorbidity; D015986:Confounding Factors, Epidemiologic; D003237:Connecticut / Q000453:epidemiology; D003866:Depressive Disorder / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment; D006801:Humans; D007484:Iowa / Q000453:epidemiology; D008297:Male; D011159:Population Surveillance; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D012934:Social Isolation; D012959:Socioeconomic Factors