What If You're Not Sleeping Like a Baby?

Alzheimers disease risk slightly increased in adults with highly fragmented sleep

/ Author:  / Reviewed by: Joseph V. Madia, MD Chris Galloway, M.D.

(RxWiki News) Waking up a few times each night is normal, whether it's just for a few seconds, a few minutes or longer. But waking up dozens of times each night may be a sign of future problems.

A recent study found that highly fragmented sleep was linked to a small increase in risk for Alzheimer's disease.

From this study, it's impossible to say if fragmented sleep contributes to Alzheimer's disease, or if poor sleep quality and Alzheimer's are linked to a different underlying problem.

Although the increase in risk was very small overall, it did not appear to be explained by coincidence or chance.

"Seek a sleep doctor's help if you're not sleeping well."

This study, led by Andrew Lim, MD, of the Division of Neurology at the University of Toronto's Sunnybrook Health Sciences Centre in Canada, looked at whether fragmented sleep might be linked to Alzheimer's disease.

The researchers tracked 737 adults who had been involved in a long-term aging study since 1997. None of the adults included in the analysis had dementia. Alzheimer's is one type of dementia.

For ten days, the adults wore devices called actigraphs, which measure their activity levels and can be used to estimate their sleep.

Each year of the study, the adults underwent testing with 19 neuropsychological tests to screen for cognitive decline or Alzheimer's disease.

Over an average of six years of follow-up time, 97 participants developed Alzheimer's disease.

The researchers compared the quality of their sleep to the quality of sleep of those who didn't develop the disease, taking into account differences in the participants' age, sex and education level.

The researchers identified a slightly higher risk for Alzheimer's disease among those who had more fragmented sleep.

Fragmented sleep means the person frequently wakes up during the night. It was measured based on the likelihood of a participant waking up during 15-second increments throughout the night.

Every person wakes up several times in the night, but waking up multiple times every hour would be highly fragmented sleep.

The researchers' methods for measuring fragmented sleep focused more on the number of times a person would wake up rather than the total time the person would spend awake during a single wakening.

They found that a person in the top 10th percentile for difficulties with fragmented sleep had about 1.5 times greater risk of developing Alzheimer's disease than someone in the lowest 10th percentile for sleep fragmentation.

In other words, those with the most severe sleep issues were a little more likely to develop Alzheimer's than those with the best sleep.

This increase in risk was not affected by individuals' age, sex or race/ethnicity.

The risk also was not affected by how much other rest time the individuals got (besides nighttime sleep), any chronic medical conditions they had or any medication they took that might affect sleep.

The researchers also calculated the extent to which fragmented sleep increased a person's risk of cognitive decline.

They found a slight increased risk for cognitive decline for every extra bit of sleep fragmentation a person experienced.

According to William Kohler, MD, a dailyRx expert and the director of the Florida Sleep Institute in Spring Hill, Florida, this study is relatively large and objective but still may have weaknesses.

"Some of the risk factors, like sleep apnea were not pointed out," Dr. Kohler said. Even though the researchers tried to account for other health conditions the participants may have had, it's likely they missed some.

Yet the underlying point of the study bears out in other research, he said.

"Again this study shows the relationship between quality of sleep and cognitive function, which we see going all the way to back to early childhood," Dr. Kohler said.

"If your sleep is disrupted, your cognitive function is going to decrease. This is pointing it out with Alzheimer's, and it was only a slight increase in risk, but it was a statistically significant one," he said.

Of course, there is an irony to the study's findings, Dr. Kohler pointed out, in light of other advice people hear about staying sharp as they age.

"There are all kinds of books out there now as far as ways to keep your mind active to help prevent cognitive decline, but this shows that it's also very important to keep your mind quiet when you sleep," he said.

"There is a need not only to keep your mind stimulated during the day but also to improve your rest at night to improve your chances of not getting dementia," Dr. Kohler said.

This study was published in the July issue of the journal Sleep.

The research was funded by the National Institute of Aging, the Illinois Department of Public Health and the Robert C. Borwell Endowment Fund.

One of the study's authors has consulted for UCB Pharm Inc. Another has consulted for Danone Inc., Wilmar Schwabe GmbH & Co., Eli Lilly Inc., Schlesinger Associates and Gerson Lehrman Group.

Review Date: 
July 29, 2013
Last Updated:
July 30, 2013