Napping and Less Disturbed Nighttime Sleep Associated with Reduced Carotid Intima-Media Thickness in Elderly Alzheimer Caregivers

Abstract

This study tested the hypothesis that disturbed or very short or long sleep durations are associated with subclinical atherosclerosis, as measured by carotid intima-media thickness (CIMT), in a sample of community-dwelling elderly spousal caregivers. Participants were 126 spousal caregivers of a person with Alzheimer's disease who underwent in-home sleep assessment by wrist actigraphy for 72 consecutive hours. Carotid artery ultrasound, also conducted in participants' homes, was used to measure CIMT in millimeters. Linear regression models including covariates related to sleep and CVD indicated that a longer daytime sleep duration was associated with significantly reduced mean common CIMT (B=-0.04, p=0.02). Specifically, for every additional hour of sleep obtained during the day, mean common CIMT was reduced by 0.04mm. Conversely, greater night time wake after sleep onset (WASO) was associated with significantly increased mean common CIMT (B=0.04, p=0.05); for each additional hour of WASO, mean common CIMT increased by 0.04mm. When combinations of sleep parameters were examined, caregivers who slept <30 minutes during the day and had ≥1 hour of WASO throughout the night had significantly greater (B=0.06, p=0.04) mean common CIMT than caregivers who slept <30 minutes during the day and had <1 hour of WASO. These analyses suggest that shorter naps and more disturbed nighttime sleep are associated with increased CIMT. Interventions that enhance sleep quantity and reduce sleep disturbance may decrease the prevalence and extent of subclinical atherosclerosis in older caregivers. Longitudinal studies with objective sleep measures that examine the effects of napping and disturbed sleep on subclinical atherosclerosis are needed.