- Sleep
disruptions – waking up and then going back to sleep during the night –
may contribute to memory and cognitive problems.
- The
duration of sleep was not considered in the study.
- Researchers
reported that cognitive issues showed up 10 years after the end of the
study.
People who experience disrupted
sleep in their 30s and 40s are more likely to have memory and cognitive
problems later in life, according to a study published in Neurology,
the journal of the American Academy of Neurology.
Researchers looked at the sleep patterns of 526
people who were followed for 11 years.
To calculate averages, the participants wore a
wrist monitor for three consecutive days, one year apart. They also reported
bedtimes and wake times in a sleep diary.
In addition, the partcipants completed a sleep
quality survey, receiving a score ranging from 0 to 21, with higher scores
indicating poorer sleep quality.
The scientists also recorded how long each
person slept each night.
Participants also completed a series of memory
and thinking tests.
Details
from the study on sleep and memory
The study included 526 participants with an
average age of 40 at baseline who were followed for 11 years. Of these, 239
people, or 46%, reported poor sleep, which was defined as having a sleep score
of greater than 5.
Researchers also looked at:
- Sleep
fragmentation, repetitive short interruptions of sleep
- The percentage of time spent moving
- The percentage of time not moving
for one minute or less
The scientists added the two percentages to
determine an average sleep fragmentation score. Overall, the participants had
an average sleep fragmentation score of 19%. The researchers then grouped the
participants based on their scores.
The researchers reported that of the 175
participants with the most disrupted sleep, 44 had poor cognitive performance
10 years after the study ended, compared to 10 of the 176 with the least
disruptive sleep.
The scientists noted that after adjusting for
age, gender, race, and education, the people with the most disruptive sleep were
more than twice as likely to have poor cognitive performance as those with the
least disruptive sleep.
They also found no differences in cognitive
performance in the middle group compared to those with the least disruptive
sleep.
The length of time people slept and
self-reported sleep quality were not associated with cognition in middle age.
Reaction to the memory and sleep study
“This important work shows how healthy brain aging is
a lifelong endeavor,” says Dr. David Merrill, a geriatric psychiatrist and director of
the Pacific Neuroscience Institute’s Pacific Brain Health Center in California
who was not involved in the study.
“Even in early adulthood, sleep quality results in measurable
changes in cognitive performance by mid-life. The study findings support the
importance of sleep quality, uninterrupted, or unfragmented sleep in relation
to cognitive performance,” Merrill told Medical News Today.
“Undoubtedly, we need a certain minimal quantity of sleep
too, but the study wasn’t a sleep lab study, so it wasn’t structured to ask
that question,” Merrill added. “Perhaps [discussing sleep patterns with my
patients and] encouraging them to use sleep
trackers so they can see for
themselves how better sleep quality relates to days with improved energy and
thinking. There are great direct-to-consumer wearables now that can allow us to
know how well we’re doing to get a good quality night’s sleep.”
The researchers reported that the most
significant limitation of the study was its small sample size. This prevented
the researchers from thoroughly investigating potential race or gender
differences.
How sleep and memory are connected
“This is a very interesting study,” said Dr. Steven Feinsilver, the director of the Center for Sleep
Medicine at Northwell Lenox Hill Hospital in New York who was not involved in
the study.
“We all know that sleep is good for you and the results of
this study are undoubtedly true. But the question is, what came first: Did poor
sleep quality cause cognitive dysfunction or did cognitive dysfunction cause
poor sleep quality?,” Feinsilver asked.
“Everyone wakes up during the night, but most people don’t
remember. We have what is called retrograde amnesia – the last few minutes
before falling asleep doesn’t make it into our long-term
memory,” Feinsilver told Medical
News Today. “This is also true of waking during the night. If we wake up
and quickly go back to sleep – which is very common – we don’t remember it.”
“There is still a lot that we don’t know about
sleep,” he added. “But the most important aspect is – how do you feel the next
day? If you typically feel good during the day, you probably get enough sleep.
The average person needs about 7.25 hours, but this is an average. Some may
need more; some may need less. People aren’t very good at assessing their own
sleep, but they can assess how they feel during the day.”
Finding a
balance between quantity and quality of sleep
It is possible that cognitive function is
related more to the quality of sleep rather than the length of time spent
sleeping.
A study. completed in
2021 at Washington University Sleep Medicine Center reported that there could
potentially be a middle range where cognitive function remained steady.
The scientists found that too little and too
much sleep could contribute to cognitive difficulties. Cognitive scores
declined in participants who slept less than 4.5 hours or more than 6.5 hours.
The association held true even after adjusting for a variety of factors,
including age, sex, and levels of Alzheimer’s proteins.
People who wake up feeling rested should not
feel compelled to change their sleep habits,
experts say.
However, those who do not sleep well might notice they have
more difficulty with cognitive tasks. Treating the
issue can potentially improve cognition.
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