Excess daytime sleepiness may signal Alzheimer's risk: Study

People who feel very sleepy during the day are nearly three times more likely to develop Alzheimer's disease than those who do not, a long-term study has found.

The study, published in the journal SLEEP, found that adults who reported being very sleepy during the day were thrice more likely to have brain deposits of beta amyloid, a protein that is a hallmark for Alzheimer's, years later.

Researchers at Johns Hopkins University in the US suggest that getting adequate nighttime sleep could be a way to help prevent Alzheimer's disease.

"If disturbed sleep contributes to Alzheimer's disease we may be able to treat patients with sleep issues to avoid these negative outcomes," said Adam P Spira, an associate professor at the Johns Hopkins Bloomberg School of Public Health.

The study used data from a long-term research started in 1958 that followed the health of thousands of volunteers as they age.

As part of the study's periodic exams, volunteers filled a questionnaire between 1991 and 2000.

Starting in 2005, some of these participants received positron emission tomography (PET) scans using Pittsburgh compound B (PiB), a radioactive compound that can help identify beta-amyloid plaques in neuronal tissue.

The researchers identified 123 volunteers who both answered the earlier questions and had a PET scan with PiB an average of nearly 16 years later.

They then analysed this data to see if there was a correlation between participants who reported daytime sleepiness or napping and whether they scored positive for beta-amyloid deposition in their brains.

Their results showed that those who reported daytime sleepiness were about three times more likely to have beta-amyloid deposition than those who did not report daytime fatigue.

After adjusting for demographic factors that could influence daytime sleepiness, such as age, sex, education, and body-mass index, the risk was still 2.75 times higher in those with daytime sleepiness, researchers said.

The unadjusted risk for amyloid-beta deposition was about twice as high in volunteers who reported napping, but this did not reach statistical significance.

It is currently unclear why daytime sleepiness would be correlated with the deposition of beta-amyloid protein, Spira said.

One possibility is that daytime sleepiness itself might somehow cause this protein to form in the brain, he said.