Poor Sleep May Raise Risk of Dementia

Recent studies reported in the American Academy of Neurology suggest that changes in brain tissue may be caused by not spending enough time in deep sleep, often exacerbated by lack of oxygen in the brain. This results in tiny abnormalities in the brain tissue — microinfarcts — which aren’t seen as often in individuals who spend more time in deep sleep. Change in sleep patterns are normal as people age, but slow-wave sleep is essential for good mental health as it helps you process new memories and remember facts. 

The Need for Deep Sleep

When you don’t breathe well, often your sleep is fractured and you don’t reach the depth of sleep that is possible when you are healthy. Conditions such as sleep apnea, emphysema and other known medical conditions can contribute to less oxygen in the brain. This can lead to tiny abnormalities in the brain called micro infarcts, essentially microscopic strokes which are less than one millimeter in size. These have been proven to be strongly related to dementia in recent studies of patients over the age of 90.

The Study

Deep or slow wave sleep in necessary to aid individuals in remembering facts and processing new memories. As people age, they spend less time in slow-wave sleep, therefore, their brain may find it more difficult to perform these tasks as their brain cells gradually die and they begin to suffer from Alzheimer’s disease and dementia. One current study gathered 167 Japanese American men (with an average age of 84 years) who were willing to have sleep tests conducted to search for changes in their brains as they aged. After they passed away approximately 6 years later, researchers performed autopsies on their brains to search for micro infarcts, loss of brain cells, the “plaques and tangles” of Alzheimer’s disease and Lewy bodies found in that form of dementia. The participants were divided into four groups, depending upon the amount of time spent with lower than normal blood oxygen levels during sleep, ranging from 13 percent for the lowest group to 70-99 percent to the highest group. Each group was comprised of 41 or 42 men.

The Results

The men in the lowest group had just four individuals with micro infarcts in the brain, while the men in the highest group showed that 14 of the 42 men suffered from abnormalities. This echoed the findings of previous studies that showed that there definitely was a link between sleep stages and dementia. Results were paralleled even when adjusting for smoking and body mass index (BMI). Those who died early in the follow-up stage and those with low scores on cognitive tests at the beginning of the study were excluded. “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, MD, DrPH, of the VA Pacific Islands Health Care System and the Pacific Health Research and Education Institute in Honolulu, Hawaii. “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 suggested that the use of a CPAP (continuous positive airway pressure) machine may improve cognition even after the development of dementia.

What Does This Mean?

The study does not suggest that breathing disorders such as sleep apnea may lead directly to dementia, but they do show that poor sleep may play a role in mental decline for some elderly adults. While past studies have suggested that sleep disturbance may lead to a risk of dementia, the reasons are still unclear.  Elderly men who had less blood circulating in their brains showed more microinfarcts (tiny strokes) in their brain, which may have contributed to their decline. The studies have shown that men who spend less time in slow-wave or deep restorative sleep seemed to show more atrophy in their brains which are more common and severe in people suffering from dementia. Be cautioned, however. “All this shows is a linkage, not cause-and-effect,” said Keith Fargo, director of scientific programs and outreach for the Alzheimer’s Association in Chicago. Other experts say that brain change have been shown but proof has yet to be provided. While treating sleep apnea may improve mental performance, no one can yet prove if boosting oxygen levels during sleep can slow down or “ward off” dementia. “If your sleep is disturbed and you’re having daytime symptoms, you should see your doctor,” Fargo said. “One reason is that you may find out your cognitive problems are not related to dementia at all.”