It’s hard to stress how important sleep is to the body. When people think of sleeping issues, they usually think of the consequences of too little sleep. But suppose that getting too much shuteye could also prove harmful?

Too Little (or Too Much) of a Good Thing

According to researchers at Washington University School of Medicine in St. Louis, people who get either too much or too little sleep may find themselves at greater risk of cognitive decline as they age.

For their research, the authors relied on volunteers who had previously participated in Alzheimer’s related studies. Because of their participation in such research, these individuals are required to undergo clinical and cognitive assessments on a yearly basis. They must also submit a blood sample in order to test for a genetic mutation linked to Alzheimer’s. As part of this particular study, these subjects were asked to not only provide samples of cerebrospinal fluid, but to also spend four to six nights wearing a tiny electroencephalogram (EEG) monitor on their foreheads.

Behind the Numbers

Using these methods, the study authors were able to document the cognitive health of 100 adults. On average, the mental well-being of these participants had been tracked for four and a half years. Out of this figure, the vast majority (88 subjects) remained in good cognitive health, showing no signs of dementia. Eleven participants were found to be suffering from very mild cognitive impairment, while the remaining subject suffered from mild dementia symptoms.

Perhaps not surprisingly, the study authors noted that those who slept less than 4.5 hours nightly experienced decline in the cognitive scores over the course of the study. However, the same was also true for those who got 6.5 hours of sleep or more each night. It should be noted that EEG devices tend to produce numbers that are an hour less than what the participants self-report.

The study’s co-author, David Holtzman, stated that “it was particularly interesting to see that not only those with short amounts of sleep but also those with long amounts of sleep had more cognitive decline. It suggests that sleep quality may be key, as opposed to simply total sleep.”

Another senior study author, Beau M. Ances, expressed similar sentiments. “I ask many of my patients, ‘How’s your sleep?’. Often patients report that they’re not sleeping well. Often once their sleep issues are treated, they may have improvements in cognition. Physicians who are seeing patients with cognitive complaints should ask them about their quality of sleep. This is potentially a modifiable factor.”