Disrupted sleep may raise risk of Alzheimer’s disease

By Dr. Ananya Mandal, MDFeb 15 2012

According to a new study, which will be presented at the American Academy of Neurology's 64th Annual Meeting in New Orleans, April 21st to April 28^th, the amount of sleep people get may later affect their memory's function and the risk of Alzheimer's.

Study author, Yo-El Ju, from the University School of Medicine, St. Louis, and a member of the American Academy of Neurology, explained, “Disrupted sleep appears to be associated with the build-up of amyloid plaques, a hallmark marker of Alzheimer's disease, in the brains of people without memory problems. Further research is needed to determine why this is happening and whether sleep changes may predict cognitive decline.”

The team of researchers analyzed the sleep patterns of 100 patients, aged between 45 and 80, who did not show any signs of dementia. 50% of these patients had a history of Alzheimer's disease in their families, the other 50% did not have any history of Alzheimer's disease in their families. The researchers placed a monitor on the patients in order to record their sleep for 2 weeks. They were also asked to record their sleeping habits and fill out surveys.

The study found that 25% of the patients showed signs of amyloid plaques, which predict Alzheimer's in the future, and can be seen many years before they are diagnosed with the progressive disease. The mean amount of time the participants slept during the study was 8 hours. However, the average was reduced - to 6.5 hours - because of disruptions in their sleep throughout the night.

In addition people who did not wake up frequently during the night were 5 times less likely to possess the amyloid plaque build-up than the people who did not sleep well. The people who did not sleep well were also found to have a greater chance of having the “markers” of early stage Alzheimer's. This means, those who spent 85% of their time in bed, sleeping soundly, have a lower risk of Alzheimer's than those who spent 85% of the time in bed tossing and turning.

Authors cautioned that it's not clear if there's a cause-and-effect relationship or, if there is, which way it runs. Ju concludes, “The association between disrupted sleep and amyloid plaques is intriguing, but the information from this study can't determine a cause-effect relationship or the direction of this relationship. We need longer-term studies, following individuals' sleep over years, to determine whether disrupted sleep leads to amyloid plaques, or whether brain changes in early Alzheimer's disease lead to changes in sleep. Our study lays the groundwork for investigating whether manipulating sleep is a possible strategy in the prevention or slowing of Alzheimer's disease”

This study was funded by the Ellison Foundation and the National Institutes of Health.

A spokeswoman for the Alzheimer's Society said, “This interesting study supports previous research that suggests regularly disrupted sleep could be linked to plaques known to develop in Alzheimer's disease. Much more research is needed, as we don't know whether these changes in people's sleep patterns over longer periods may increase chances of cognitive decline and dementia. Those of us who may have to count sheep at times should not panic. The best way to reduce your risk of dementia is to eat healthily, take regular exercise, don't smoke and get your blood pressure and cholesterol checked.”

Alzheimer's disease begins long before there any symptoms, the researchers noted, but signs of the beta-amyloid plaques that build up in the brains of Alzheimer's patients can be detected in some cognitively normal people. “This [study] is another indication there are early brain changes [in Alzheimer's disease],” says Maria Carrillo, senior director of medical and scientific relations for the Alzheimer's Association. Which way the association develops is yet to be determined, she says. “The trouble sleeping could reflect brain changes happening,” Carrillo tells WebMD.

Such research is critical for the study of Alzheimer's disease, commented Judy Willis, an educator and neurologist in Santa Barbara, Calif., and a member of the neurology academy. “Interventions, once the disease has progressed to symptomatic diagnosis, are limited and there is no cure or even strong support for any treatment that can reverse the development of amyloid plaques in humans once they form.” But it may be possible to intervene at an earlier stage, especially if it turns out the disordered sleep actually causes the amyloid pathology, Willis said. “Studies finding correlation are inadequate to confirm causality,” she noted, adding it's equally possible that disrupted sleep has a role in the development of the disease or that it's an early sign of a disease already developing.