This study involved 526 participants with an average age of 40 years old who were followed for 11 years, who had their sleep duration and quality examined, and wore wrist activity monitors for 3 consecutive days on two occasions one year apart to calculate their averages. According to the researcher the participants slept for an average of 6 hours.
The participants kept a sleep diary to record bedtimes, and wake times, as well as complete sleep quality surveys with scores ranging from zero (good) to 21 (poor). 239 participants reported poor sleep with scores greater than 5. The participants also completed a series of memory and thinking tests.
The researchers looked for sleep fragmentation, the percentage of time spent moving and the percentage of time spent moving for one minute or less during sleep. After adding the percentages together, the participants were found to have an average sleep fragmentation of 19%. The participants were divided into three groups based on their sleep fragmentation scores.
Of the 175 with the most disrupted sleep, 44 had poor cognitive performance 10 years later, compared to 10 of the 176 people with the least amount of disrupted sleep. After the researchers adjusted for various factors such as education, gender, race, and age, those with the most disrupted sleep were found to have more than twice the odds of having poor cognitive performance compared to those with the least disrupted sleep. No difference was found in cognitive performance at midlife for those in the middle group compared to those in the group with the least disrupted sleep.
“More research is needed to assess the link between sleep disturbances and cognition at different stages of life and to identify if critical life periods exist when sleep is more strongly associated with cognition,” Leng said. “Future studies could open up new opportunities for the prevention of Alzheimer’s disease later in life.”
It was noted that the amount of time people slept and their own reports of the quality of sleep were not associated with cognition in middle age. It was also noted that this study does not prove that sleep quality causes cognitive decline, it only shows an association.
