Researchers are increasingly looking at sleep disorders and how sleep impacts brain health. For a long time, scientists have been trying to figure out what causes Alzheimer’s disease, and a recent discovery suggests that poor sleep quality could be a contributing factor to the development of Alzheimer’s disease and other forms of dementia. In particular, researchers are looking at how missed sleep is associated with a particular protein in the brain.
Tau is a protein that stabilizes the structure of nerves in the brain. It comes in at least two forms. When an abnormal form of tau develops, it causes the interior structures of a nerve cell to fall apart. The abnormal tau proteins clump, forming a tangle or plaque. These plaques are seen in people with Alzheimer’s disease, Lewy body disease and frontal lobe dementia.
In a healthy person who gets enough sleep, the brain clears out the abnormal form of tau and excess tau that it doesn’t need. Sleep is when the brain handles this and many other housekeeping types of tasks that are essential for brain health. When sleep cycles are disordered or disrupted, the brain isn’t able to clean out the internal garbage that builds up during the day. In a person who misses sleep, the brain also misses out on its chance to clean out the abnormal tau and other waste products.
Sleep deprivation not only slows the removal of abnormal tau, but it might also cause the body to generate even more tau. In a small study of patients in 2017, just one night of missed sleep caused their bodies to up the production protein beta amyloid. This protein is associated with Alzheimer’s disease plaques. When those patients were deprived of sleep for a full week, their bodies increased production of tau and lower the rate of tau removal.
In healthy, middle-aged men who missed one night of sleep, participants experienced a 17 percent increase of tau in their blood. The study also included a control group. The men in the control group were matched for age, race, weight, vital signs and socio-economic status. The men in the control group were allowed to get a good night’s rest. They experienced a 2 percent increase of tau in their blood.
The increase of tau in the blood does not mean that tau causes Alzheimer’s disease or any other form of dementia. Researchers aren’t sure why the level of tau increases. It’s possible that the brain clears tau out of the nerves and sends it into the bloodstream. Researchers aren’t sure yet of high tau levels in the blood are a problem, or if it is just the tau in the brain that is a problem.
Researchers admit that more aspects of tau and its relationship to dementia and Alzheimer’s disease need to be examined. There are also additional factors of sleep and Alzheimer’s disease that researchers want to consider. The scientists who published their study results noted that even though people spend about one-third of their lives asleep, the processes that take place during sleep are poorly understood. More research is needed on the relationship between sleep and dementia.