People who have trouble falling asleep may be at greater risk of developing cognitive problems or dementia than their counterparts who sleep well, a research review suggests.
Researchers examined data on 51 previously published studies that examined middle-aged and older people in North America, Europe and east Asia to see if sleep issues were associated with cognitive health over time.
Individuals with insomnia were 27% more likely to develop cognitive problems, the review found. People who had what’s known as sleep inadequacy, or an insufficient amount of quality rest, were 25% more likely to develop dementia, the researchers also found.
Sleep inefficiency, or spending too much time wide awake in bed, was associated with a 24% greater chance of cognitive decline, the team reported in the Journal of Neurology, Neurosurgery and Psychiatry.
“These findings suggest that sleep management might serve as a promising target for dementia prevention,” said lead study author Wei Xu of Qingdao University in China.
While the study wasn’t designed to determine whether or how sleep problems directly cause cognitive decline or dementia, there are several possible explanations, according to Wei.
Sleep problems might lead to cognitive impairment by causing inflammation of tissue in the central nervous system, including the brain and spinal cord. Sleep difficulties might also lead to cognitive problems by causing or exacerbating cerebral hypoxia, a reduction in oxygen supply in the brain, Wei said.
In addition, sleep problems could make the brain less efficient at removing waste and contribute to loss of brain cells or atrophy in key regions.
Most of the studies in the report followed participants for anywhere between three and 10 years, and a few tracked subjects for decades. Participants were typically aged 50 or older at the start of the studies, and they were often in their seventies.
Sleep apnea, a sleep disorder in which breathing repeatedly stops and starts, was associated with a 29% higher risk of cognitive problems.
Spending a long time in bed was tied to a 15% greater chance of cognitive impairment.
People who slept around six or seven hours a night appeared to have the lowest risk of cognitive disorders, while the risk was elevated for people who slept less than four hours or more than 10 hours a night. – Reuters
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