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Objectively measured sleep quality and functional impairment in family caregivers of older adults with memory disorders
Annals of General Psychiatryvolume 7, Article number: S246 (2008)
Poor sleep quality has been linked to functional impairment in several populations [1–4] but this association has not been investigated widely in family caregivers of older adults with memory disorders. We investigated the association between objectively measured sleep and functional status in a sample of family caregivers.
Materials and methods
Participants were 42 caregiver-patient dyads. Caregivers completed the Beck Depression Inventory (BDI-II)  and the Medical Outcomes Study SF-36 . The “physical function” subscale of the SF-36 measures difficulty lifting groceries, climbing stairs, etc. Scores range from 1 to 100; higher scores indicate better function. Caregivers completed 1 week of actigraphy–an objective means of measuring sleep by recording movement. We calculated their total sleep time (TST; mean time asleep while in bed) and sleep efficiency (SE; mean percentage of time asleep while in bed).
Caregivers' mean age was 69.4 ±13.6 years. Patients' mean age was 79.8 ±7.6 years; their mean Mini-Mental State Exam  score was 21.3 ± 4.9. Caregivers' mean physical function score was 72.6 ±23.2. In regression analyses (adjusted for age, self-rated health, and BDI-II), each 1-hour increase in TST was associated with a 5.7-point increase in physical function (Beta=5.71, p=.001, R-squared=.75), and each 10% increase in SE predicted a 3.8-point increase in physical function (Beta=3.79, p=.02, R-squared=.69).
In family caregivers, greater TST and SE were independently associated with better physical function after controlling for potential confounders. Future, longitudinal studies are needed to establish the directions of these relationships and to evaluate whether poor sleep might be a preventable cause of disability in caregivers.
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Research supported by the Medical Research Service of the Palo Alto Veterans Affairs Health Care System, by the Department of Verterans Affairs Sierra Pacific MIRECC, and by AG21134.