Sleep and biomarkers of atherosclerosis in elderly Alzheimer caregivers and controls.

BACKGROUND Perturbed sleep might contribute to cardiovascular disease by accelerating atherosclerosis. Sleep is poor in Alzheimer caregivers who are also a group at increased cardiovascular risk. OBJECTIVE To test the hypothesis that impaired sleep relates to elevated levels of biomarkers of atherosclerosis in community-dwelling elderly and that this association would possibly be stronger in caregivers than in non-caregiving controls. METHODS We studied 97 Alzheimer caregivers and 48 non-caregiving controls (mean age 71 +/- 8 years, 72% women) who underwent wrist actigraphy at their homes. Measures of objective sleep were averaged across 3 consecutive nights. The Pittsburgh Sleep Quality Index was administered by an interviewer to rate subjective sleep quality. Morning fasting blood samples were collected to determine measures of inflammation, coagulation and endothelial dysfunction. RESULTS There were independent associations between decreased subjective sleep quality and increased levels of fibrin D-dimer (p = 0.022, DeltaR(2) = 0.029) and von Willebrand factor antigen (p = 0.029, DeltaR(2) = 0.034) in all participants. Percent sleep (p = 0.025) and subjective sleep quality (p = 0.017) were lower in caregivers than in controls. In caregivers, the correlation between decreased percent sleep and elevated levels of interleukin-6 (p = 0.042, DeltaR(2) = 0.039) and C-reactive protein (p < 0.10, DeltaR(2) = 0.027) was significantly stronger than in controls. CONCLUSION Perceived impairment in sleep related to increased coagulation activity and endothelial dysfunction in all participants, whereas objectively impaired sleep related to inflammation activity in caregivers. The findings provide one explanation for the increased cardiovascular risk in elderly poor sleepers and dementia caregivers in particular.