People who experience more sleep disturbances in their 30s and 40s may be more likely to have memory and thinking problems a decade later, according to new research. The study, published in the journal Neurology, does not prove that sleep quality causes cognitive decline. It shows only one association.
“As symptoms of Alzheimer’s disease begin to accumulate in the brain decades before symptoms begin, understanding the connection between sleep and cognition earlier in life is important to understand the role of sleep problems as a risk factor for the disease,” said Yu Leng. , from the University of California, San Francisco.
“Our findings indicate that quality rather than quantity of sleep is more important for cognitive health in middle age,” Leng added. The study involved 526 people over the age of 40. They were followed for 11 years.
Researchers looked at participants’ sleep duration and quality. Participants wore a wrist activity monitor for three consecutive days over a period of approximately one year to calculate their average. Participants slept an average of six hours.
Participants also reported bedtimes and wake times in a sleep diary and completed a sleep quality survey with scores ranging from zero to 21, with higher scores indicating poorer sleep quality. A total of 239 people, or 46 percent, reported poor sleep with a score greater than five.
Participants completed a series of memory and thinking tests.
The researchers also looked at sleep fragmentation, which measures repetitive brief interruptions of sleep. They looked at both the percentage of time spent moving and the percentage of time spent not moving for a minute or less during sleep.
After adding these two percentages together, the researchers found that the participants had an average sleep fragmentation of 19 percent. The researchers then divided the participants into three groups based on their sleep fragmentation scores.
Of the 175 people with the most disturbed sleep, 44 had lower cognitive performance 10 years later, compared to 10 of 176 people with less sleep disturbance.
After adjusting for age, sex, race, and education, those with the most sleep disruption were more than twice as likely to have poor cognitive performance as those with the least sleep disruption.
There was no difference in cognitive performance at midlife between the moderate group compared to the low sleep group.