Scientists have found that people who don't sleep much or are suffering from sleep apnea were possibly likelier to develop dementia.
According to the new study, people who don't have as much oxygen in their blood during sleep, which occurs with sleep apnea and conditions such as emphysema, were 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.
In addition, people who spent less time in deep sleep, called slow wave sleep, were more likely to have loss of brain cells than people who spent more time in slow wave sleep. Slow wave sleep is important in processing new memories and remembering facts. People tend to spend less time in slow wave sleep as they age. Loss of brain cells is also associated with Alzheimer's disease and dementia.
For the study, 167 Japanese American men had sleep tests conducted in their homes when they were an average age of 84. 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 participants were divided into 4 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.
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.
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Study author Rebecca P. Gelber, MD, DrPH, said that the findings suggested that low blood oxygen levels and reduced slow wave sleep may contribute to the processes that lead to cognitive decline and dementia. More research was 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.
The study is published in the online issue of Neurology.