['To examine the relationship between changes in objectively assessed sleep and global cognitive functioning from inpatient postacute rehabilitation to 6-month follow-up.', 'Secondary analysis of two prospective, longitudinal studies.', 'Inpatient rehabilitation units at a Veterans Affairs Medical Center.', 'Older adults (mean age 73.8 ± 9.4) undergoing inpatient rehabilitation (n = 192).', 'All participants completed 7 nights and days of ambulatory sleep monitoring using wrist actigraphy (yielding an estimate of nighttime wakefulness and daytime sleep) and the Mini-Mental State Examination (MMSE) during a postacute inpatient rehabilitation stay and 6 months after discharge. The 5-item Geriatric Depression Scale, Geriatric Pain Measure, and Cumulative Illness Rating Scale for Geriatrics were completed during inpatient rehabilitation.', 'Growth curve modeling (controlling for baseline age, education, sex, body mass index, depression, pain, and comorbidity burden) revealed that individuals whose amount of daytime sleep decreased from inpatient postacute rehabilitation to 6-month follow-up also experienced improvements in MMSE score (β = -0.01, t(80 = -3.22, P = .002)). Change in nighttime wakefulness was not a significant predictor of change in MMSE score.'] Is decrease in daytime sleeping associated with improvement in cognition after hospital discharge in older adults?