3 Studies Link Sleep Issues to Cognitive Impairment
Having sleep issues? Several studies that were just presented at the Alzheimer’s Associations International Conference suggest that sleep problems are significantly associated with cognitive impairment. And by sleep issues, we’re talking not just about insomnia, but sleeping too much, having abnormal breathing during sleep, and excessive daytime sleepiness.
Too Much or Too Little Sleep?
One of these studies involved data from the Nurses’ Health Study, which involved more than 15,000 female participants for a period of time as they aged. The researchers out of Brigham and Women’s Hospital in Boston assessed the study participants’ cognitive ability using six separate tests. These tests were administered when the study participants had reached at least 70 years of age and were repeated every two years during a six-year period. Additionally, researchers ask the women about their sleep duration around the time the first tests were administered.
The researchers found that the women’s average amount of sleep was seven hours a day. Their analysis determined that women who reported sleeping five hours or less had significantly lower cognitive assessments than those who slept an average of seven hours. And surprisingly, participants who slept for nine hours or more also had significantly lower cognitive assessments.
Another study out of the University of California San Francisco followed 1,430 older women who were participating in Study of Osteoporotic Fractures. This group of women was monitored during sleep to evaluate the quality and length of their sleep, when they awoke and their breathing. The researchers also assessed these women’s cognitive function to identify mild cognitive impairment or dementia. The researchers found that women who had sleep-disordered breathing (which is a group of disorders characterized by abnormalities of respiratory patterns such as obstructive sleep apnea, according to the National Center on Sleep Disorders Researcher) were approximately twice as likely to receive a diagnosis of cognitive impairment or dementia. Additionally, the participants who woke the most often after falling asleep as well as those who were less “sleep efficient” (which means the ratio of time spent sleeping compared to the time spent awake) were approximately three times at risk of entering a nursing home as compared to those who slept soundly through the night.
A third study out of France followed 4,900 people who were at least 65 years of age over a 10-year period. The study participants were evaluated physically and mentally and also took part in interviews about their lifestyle, including any sleep issues such as falling asleep, staying asleep, and sleepiness during the day that they were experiencing. The participants also rated their sleep quality and identified recent insomnia episodes. The researchers found that participants who said they were frequently sleepy during the day were more likely to have cognitive decline. However, participants who had difficulty staying asleep or who had frequent insomnia were less likely to have cognitive decline during follow-up visits to the researchers.
While none of these studies has been published in a medical journal and are thus considered preliminary, the combination of the studies is striking. MedPage Today quotes Dr. Constantine Lyketsos of Johns Hopkins University as saying, “It’s unusual that we have [multiple] studies coming together at the same time to say the same thing, which is that sleep disruptions of various kinds throughout the lifespan are probably accelerators of cognitive aging and risk factors for dementia.”
Primary Sources for This Sharepost:
Alzheimer's Association. (2012). Sleep duration, sleep disorders, and circadian patterns are risk factors and indicators of cognitive decline.
CBS DC. (2012). Large-scale sleep study links lack of sleep to Alzheimer’s and mental deterioration.
Gever, J. (2012). Bad sleep tied to cognitive decline. MedPage Today.
National Center for Sleep Disorders Research. (N.D.) Sleep-disordered breathing.