A new study has found that women in their 80s who become more sleepy during the day over time may face a higher risk of developing dementia.
The research, published in the journal Neurology®, which is part of the American Academy of Neurology, adds to growing evidence that sleep plays an important role in brain health, especially in older age.
Scientists have long known that good sleep helps the brain rest and recover. During sleep, the brain processes memories, clears waste, and supports thinking ability. However, researchers are still trying to understand how changes in sleep over many years might be linked to memory problems and diseases like dementia.
In this study, researchers focused on older women and followed their sleep patterns over five years. The team was led by Dr. Yue Leng from the University of California, San Francisco. She explained that while sleep is clearly important, the exact relationship between sleep changes and dementia is still not fully understood.
The study included 733 women with an average age of 83. At the start of the study, none of the participants had dementia or serious memory problems. Over the next five years, the researchers tracked both their sleep habits and their brain health. By the end of the study, 164 women had developed mild memory problems, and 93 had been diagnosed with dementia.
To measure sleep, the participants wore small devices on their wrists. These devices recorded when they slept, how long they slept, and how their body rhythms changed throughout the day and night. This gave researchers a detailed picture of both nighttime sleep and daytime activity.
The scientists looked at several aspects of sleep. They studied how long the women slept at night, how often they woke up, how much they napped during the day, and how stable their daily body rhythms were. These rhythms, also known as circadian rhythms, help control when we feel awake or sleepy.
After five years, the researchers found that more than half of the women had noticeable changes in their sleep patterns. They grouped the women into three categories based on how their sleep changed over time.
About 44% of the women had stable sleep or slightly improved sleep. Around 35% experienced worse sleep at night, meaning they slept less, woke up more often, and tended to nap more during the day.
The remaining 21% showed a pattern of increasing sleepiness. These women slept more during both the day and night, had poorer sleep quality, and showed weaker daily rhythms.
The researchers then compared how many women in each group developed dementia. In the group with stable sleep, 8% developed dementia. In the group with worse nighttime sleep, 15% developed dementia. In the group with increasing sleepiness, 19% developed dementia.
After taking into account other factors such as age, education, race, and health conditions like diabetes and high blood pressure, the researchers found a clear result. Women whose sleepiness increased over time had about twice the risk of developing dementia compared to those whose sleep remained stable.
Interestingly, the group that had worse sleep at night did not show a significantly higher risk of dementia. This suggests that simply having poor sleep may not be as important as changes in overall sleep patterns, especially increasing sleepiness during the day.
Dr. Leng noted that sleep patterns can change quite quickly in older adults, even over just a few years. She suggested that future research should look at the full picture of sleep, including daytime naps, sleep quality, and daily rhythms, rather than focusing only on nighttime sleep.
It is important to understand that this study shows a connection, not a cause. This means that increasing sleepiness does not necessarily cause dementia. Instead, it may be an early sign of changes in the brain that later lead to memory problems.
The study also had some limitations. Most of the participants were white, so the results may not apply to people from more diverse backgrounds. More research is needed to confirm these findings in different populations.
The research was supported by the National Institutes of Health and the National Institute on Aging. It highlights the importance of paying attention to sleep changes in older age, as they may offer early clues about brain health.
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