Spending less time in slow-wave or deep sleep is linked to the loss of brain cells that can lead to dementia, a new study finds.
Slow-wave sleep, which occurs mostly in the first three hours of the night, is when the brain processes thoughts and memories.
The study also found that people with lower levels of oxygen in their blood — typical those with sleep apnea or emphysema — were more likely to have brain abnormalities that lead to dementia.
To reach these conclusions, published in the journal Neurology, the researchers carried out sleep tests on 167 men with an average age of 84 (Gelber et al., 2014).
All the men in the study were followed up until death, when brain cell loss and any abnormalities associated with Alzheimer’s disease were assessed.
Men who spent the shortest time in slow-wave sleep were more than twice as likely to have brain cell loss as those who had the most slow-wave sleep.
Similarly, men whose blood-oxygen levels were the lowest were seven times more likely to have abnormalities in their brain that are associated with dementia.
The results also showed that those who got the most slow-wave or deep sleep performed better on tests of both thinking and memory.
Dr. Rebecca P. Gelber, who led the study, said:
“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.
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.”
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