Extreme sleep durations may affect brain health in later life

BOSTON, MA - A new research study led by Brigham and Women's Hospital (BWH) published in The Journal of the American Geriatrics Society in May, shows an association between midlife and later life sleeping habits with memory; and links extreme sleep durations to worse memory in later life. The study suggests that extreme changes in sleep duration from middle age to older age may also worsen memory function.

"Sleep Duration In Midlife and Later Life In Relation to Cognition: The Nurses' Health Study," led by Elizabeth Devore, ScD, instructor in medicine in the Channing Division of Network Medicine at BWH found that women who slept five or fewer hours, or nine or more hours per day, either in midlife or later life, had worse memory, equivalent to nearly two additional years of age, than those sleeping seven hours per day. Women whose sleep duration changed by greater than two hours per day over time had worse memory than women with no change in sleep duration.

This study was the first to evaluate associations of sleep duration at midlife and later life, and change in sleep duration over time, with memory in 15,263 participants of the Nurses' Health Study. Participants were female nurses, aged 70 or older and were free of stroke and depression at the initial cognitive assessment.

"Given the importance of preserving memory into later life, it is critical to identify modifiable factors, such as sleeping habits, that may help achieve this goal," Devore stated. "Our findings suggest that getting an 'average' amount of sleep, seven hours per day, may help maintain memory in later life and that clinical interventions based on sleep therapy should be examined for the prevention of cognitive impairment."

Specifically, researchers report that:

• Extreme sleep durations may adversely affect memory at older ages, regardless of whether they occur at mid-life or later-life.
• Greater changes in sleep duration appear to negatively influence memory in older adults.
• Women with sleep durations that changed by two or more hours per day from midlife to later life performed worse on memory tests than women with no change in sleep duration, equivalent to being one to two years older in age, compared to those whose sleep duration did not change during that time period.

"These findings add to our knowledge about how sleep impacts memory," said Devore. "More research is needed to confirm these findings and explore possible mechanisms underlying these associations."

The research study was conducted within the Nurses' Health Study, with funding for this cohort from the National Institutes of Health (P01 CA87969).

Brigham and Women's Hospital (BWH) is a 793-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare. BWH has more than 3.5 million annual patient visits, is the largest birthing center in Massachusetts and employs nearly 15,000 people. The Brigham's medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in patient care, quality improvement and patient safety initiatives, and its dedication to research, innovation, community engagement and educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Biomedical Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, more than 1,000 physician-investigators and renowned biomedical scientists and faculty supported by nearly $650 million in funding. For the last 25 years, BWH ranked second in research funding from the National Institutes of Health (NIH) among independent hospitals. BWH continually pushes the boundaries of medicine, including building on its legacy in transplantation by performing a partial face transplant in 2009 and the nation's first full face transplant in 2011. BWH is also home to major landmark epidemiologic population studies, including the Nurses' and Physicians' Health Studies and the Women's Health Initiative. For more information, resources and to follow us on social media, please visit BWH's online newsroom.