Five Hours or Less of Sleep Associated With Increased Risk of Dementia, Death in Older Adults

Adults 65 years and older who reported getting 5 hours or less of sleep per night exhibited a more than 2-fold increased risk of dementia than those who reported 7 to 8 hours of sleep, according to study findings published in Aging.

In examining the potential link between sleep and dementia, a prior study indicated that impaired sleep may increase the risk of Alzheimer disease (AD), which is the most common cause of dementia. Moreover, researchers of the present study highlight that sleep disturbance and insufficiency have been shown to be associated with both the development and progression of AD and with all-cause mortality, but conflicting results on the relationship have been reported.

As the National Sleep Foundation finds that adults 65 years and older report more sleep disturbance than any other age group, researchers sought to further examine whether sleep quality and duration may be linked with dementia and all-cause mortality among these populations.

Using nationally representative data derived from older adults taking part in the National Health and Aging Trends Study (NHATS), a longitudinal study of Medicare beneficiaries 65 years and older, researchers assessed the 5-year relationship between sleep disturbance and deficiency with incident dementia and all-cause mortality among randomly selected NHATS participants (N = 2812).

Respondents answered sleep questionnaires in 2013 and 2014 on several characteristics of sleep disturbance and deficiency, including alertness, nap frequency, time to sleep onset, sleep quality (indicated as very good, good, fair, poor, and very poor), sleep duration, and snoring.

Responses were analyzed over the following 5 years via Cox proportional hazard ratios (HR), adjusting for confounders such as marital status, chronic conditions, body weight, and depressive symptoms.

Compared with the reference point of 7 to 8 hours in sleep duration, participants who reported very short sleep duration of 5 hours or less were more than twice as likely to be associated with incident dementia in adjusted Cox models (HR, 2.04; 95% CI, 1.26-3.33). Additionally, respondents who reported taking 30 minutes or longer to fall asleep were at a 45% greater risk for incident dementia (HR, 1.45; 95% CI, 1.03-2.03) compared with those who took less than 15 minutes for sleep onset.

"Our findings illuminate a connection between sleep deficiency and risk of dementia and confirm the importance of efforts to help older individuals obtain sufficient sleep each night," said lead study author Rebecca Robbins, PhD, of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital (BWH), in a statement.

Several of the sleep disturbance and deficiency variables were found to be linked with all-cause mortality in adjusted Cox models:

• difficulty maintaining alertness (some days: HR, 1.49; 95% CI, 1.13-1.94; most/every day: HR, 1.65; 95% CI, 1.17-2.32)
• nap frequency (some days: HR, 1.38; 95% CI, 1.03-1.85; most/every day: HR, 1.73; 95% CI, 1.29-2.32)
• sleep quality (poor/very poor: HR, 1.75; 95% CI, 1.17-2.61)
• very short sleep duration of 5 hours or less (HR, 2.38; 95% CI, 1.44-3.92)

Senior study author Charles Czeisler, MD, PhD, FRCP, FAPS, chief of the Division of Sleep and Circadian Disorders at BWH, also noted in a statement that participants 76 years and older may represent an at-risk population, as those who were sleep deficient at baseline were associated with double the risk of incident dementia and all-cause mortality over the next 4 to 5 years.

"These data add to the evidence that sleep is important for brain health and highlight the need for further research on the efficacy of improving sleep and treating sleep disorders on the risk of AD and mortality," said Czeisler.

Reference

Robbins R, Quan SF, Weaver MD, Bormes G, Barger LK, Czeisler CA. Examining sleep deficiency and disturbance and their risk for incident dementia and all-cause mortality in older adults across 5 years in the United States. Aging. Published online February 11, 2021. doi:10.18632/aging.202591