Abstract
OBJECTIVES: To determine whether subjective poor sleep prospectively increases functional limitations and incident disability in a national sample of adults living in the United States. DESIGN: Prospective cohort. SETTING: Longitudinal Survey of Midlife Development in the United States (MIDUS). PARTICIPANTS: Young, middle-aged, and older men and women (aged 24-75) surveyed in 1995/96 (MIDUS 1) and followed up in 2004-06 (MIDUS 2). Complete data were available for 3,620 respondents. MEASUREMENTS: Data were from telephone interviews and self-administered questionnaires. Participant reported chronic sleep problems within the prior month; functional limitations were assessed using the Functional Status Questionnaire. Demographic (age, sex, race), socioeconomic (educational attainment), health (chronic conditions, depression), and health behavior (obesity, smoking) covariates were assessed to reduce potential confounding. RESULTS: Approximately 11% of the sample reported chronic sleep problems at both MIDUS waves. Average number of activity of daily living (ADL) and instrumental activity of daily living (IADL) limitations increased significantly between MIDUS 1 (ADL limitations: 0.06; IADL limitations: 0.95) and MIDUS 2 (ADL limitations: 0.15; IADL limitations: 1.6; P < .001). Adjusted regression models estimating change in ADL scores showed that chronic sleep problems at MIDUS 1 predicted significantly greater increases in ADL (incident rate ratio (IRR) = 1.55, P < .001) and IADL (IRR = 1.28, P < .001) limitations. In those with no functional limitations at baseline, logistic regression models showed that chronic sleep problems significantly increased the odds of incident ADL (odds ratio (OR) = 2.33, 95% confidence interval (CI) = 1.68-3.24, P < .001) and IADL (OR = 1.70, 95% CI = 1.21-2.42, P = .002) disability. CONCLUSION: Reports of chronic sleep problems predicted greater risk of onset of and increases in functional limitations 9 to 10 years later. Poor sleep may be a robust and independent risk factor for disability in adults of all ages.