A new study has found that people who have sleep apnea or spend less time in deep sleep may be more likely to have changes in the brain associated with dementia.
According to the study’s findings, people who don’t have as much oxygen in their blood during sleep, which occurs with sleep apnea and conditions such as emphysema, are more likely to have tiny abnormalities in brain tissue, called micro infarcts, than people with higher levels of oxygen in the blood.
These abnormalities are associated with the development of dementia, explain researchers with the VA Pacific Islands Health Care System and the Pacific Health Research and Education Institute in Honolulu, Hawaii.
Additionally, the study found that people who spent less time in deep sleep, called slow wave sleep, were more likely to experience the loss of brain cells than people who spent more time in slow wave sleep. Loss of brain cells is also associated with Alzheimer’s disease and dementia.
Slow wave sleep is important in processing new memories and remembering facts, according to the researchers. Unfortunately, as we age, we spend less time in slow wave sleep.
For the study, the researchers recruited 167 Japanese-American men with an average age of 84, who had sleep tests conducted in their homes. All were followed until they died an average of six years later, and autopsies were conducted on their brains to look for micro infarcts, loss of brain cells, the plaques and tangles associated with Alzheimer’s disease, and Lewy bodies found in Lewy body dementia, the researchers report.
The researchers divided the men into four groups based on the percentage of time spent with lower than normal blood oxygen levels during sleep. The lowest group spent 13 percent of their time or less with low oxygen levels, while the highest group spent 72 to 99 percent of the night with low oxygen levels. Each group had 41 or 42 men.
Of the 41 men in the lowest group, four had micro infarcts in the brain, while 14 of the 42 men in the highest group had the abnormalities, making them nearly four times more likely to have brain damage, the researchers discovered.
The men were again divided into four groups based on the percentage of the night spent in slow wave sleep. Of the 37 men who spent the least time in slow wave sleep, 17 had brain cell loss, compared to seven of the 38 men who spent the most time in slow wave sleep, according to the study’s findings.
The results remained the same after adjusting for factors such as smoking and body mass index and after excluding participants who had died early in the follow-up period, and those who had low scores on cognitive tests at the beginning of the study, according to the researchers.
“These findings suggest that low blood oxygen levels and reduced slow wave sleep may contribute to the processes that lead to cognitive decline and dementia,” said study author Rebecca P. Gelber, M.D., Dr.P.H.
“More research is needed to determine how slow wave sleep may play a restorative role in brain function and whether preventing low blood oxygen levels may reduce the risk of dementia.”
Gelber noted that a previous study showed that using a continuous positive airway pressure machine (CPAP) for obstructive sleep apnea may improve cognition, even after dementia has developed.
The study, which was supported by the National Institute on Aging, Alzheimer’s Association, Hawaii Community Foundation and Department of Veterans Affairs Pacific Islands Health Care System, was published in Neurology, the medical journal of the American Academy of Neurology.