MrOS study links poor sleep quality to cognitive decline in older men

California Pacific CURRENTS: The online journal of CPMC Research Institute

Research by Terri Blackwell and Katie Stone, Ph.D., highlights the importance of sleep quality in preventing cognitive decline in the elderly

Since almost half of older adults report habitual sleep problems, and at least 10 per cent of people older than 65 years will develop cognitive impairment, investigators at CPMCRI are seeking new ways to determine prospective associations between sleep and cognitive decline.

In April 2015, new results published in the journal Sleep showed that higher levels of fragmented sleep and lower sleep efficiency were associated with a 40 to 50 per cent increase in the risk of clinically significant decline in cognitive function over three to four years. Sleep duration, however, was not related to cognitive decline.  “Our study provides new evidence supporting the importance of sleep quality in preventing cognitive decline over time, especially in older people,” says Terri Blackwell, study author and a Senior Statistician at CPMCRI.

In the population-based, longitudinal study, Blackwell and colleagues measured sleep parameters in 2,822 men free of cognitive impairment aged 67 years and older who were enrolled in the multicenter Outcomes of Sleep Disorders in Men (MrOS Sleep) Study. Objectively measured sleep data including total sleep time, sleep efficiency, wake after sleep onset, and number of long-wake episodes were collected from study participants over an average of five nights’ sleep, using wrist actigraphy (a ‘sleep watch’ device).

Cognitive function was assessed by evaluation of attention and executive function (i.e., abstract thinking, and the ability for decision making) using the Trails B test. Results were adjusted for depressive symptoms, comorbidities, medication use and other potential confounding factors. “The effect of lower levels of sleep quality on cognitive decline seen in our study is equivalent to the effects of a five-year increase in age,” says Katie Stone, Ph.D., lead
author and a Senior Scientist at CPMCRI. “With this study we’re seeing a reminder that—as a key factor in a healthy lifestyle—sleep is essential for optimal cognitive functioning.”

Dr. Stone notes that the findings may not be generalized to other populations other than community-dwelling older men, and that more research is needed to determine if these associations hold after longer follow-up.

The study was funded by the National Institutes of Health (NIH) with support for the MrOS Sleep study from National Heart, Lung, and Blood Institute (NHLBI), as well as from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the National Institute on Aging (NIA), and the National Cancer Institute (NCI).