Many people expect their sleep to change as they get older. Older adults often go to bed earlier, wake up more during the night, and may feel the need to take naps during the day.
These changes can seem like a normal part of aging. However, a new study suggests that a growing need for sleep during the day could be more than just a sign of getting older. It may also be linked to a higher risk of dementia.
The study was published in Neurology®, the medical journal of the American Academy of Neurology. Researchers found that women in their 80s who became much sleepier during the day over several years were about twice as likely to develop dementia as women whose sleep patterns stayed stable.
The researchers stressed that this study only found a relationship between increasing sleepiness and dementia. It does not prove that sleeping more causes dementia.
The research was led by Dr. Yue Leng from the University of California, San Francisco. She explained that sleep plays an important role in keeping the brain healthy. During sleep, the brain carries out many important jobs.
It helps store memories, clears away waste products, and allows brain cells to recover and work properly. Scientists know that poor sleep and memory problems are connected, but they are still trying to understand exactly how these changes influence one another as people age.
The study included 733 women with an average age of 83 years. At the beginning of the study, none of the participants had dementia or signs of major memory loss. The researchers followed them for five years to observe changes in both their sleep and their brain health.
To measure sleep, the women wore small devices on their wrists that recorded their sleeping patterns and daily activity. These devices allowed the researchers to monitor how long the women slept, how often they woke up during the night, how much they napped during the day, and how regular their natural body clocks were.
The body’s internal clock, often called the circadian rhythm, helps control when people feel sleepy and when they feel alert.
Over the five years, sleep patterns changed greatly for many participants. More than half of the women showed major changes in their sleeping habits. The researchers placed the women into three groups. About 44 percent had sleep patterns that stayed stable or even improved slightly.
Around 35 percent experienced worsening nighttime sleep, including shorter sleep, more waking during the night, and more daytime naps. The remaining 21 percent became increasingly sleepy, sleeping more during both the day and the night while also having poorer sleep quality and more disturbed daily rhythms.
During the study period, 164 women developed mild memory and thinking problems, while 93 women were diagnosed with dementia. Dementia is not a single disease. It is a general term for conditions that cause serious problems with memory, thinking, and everyday activities. Alzheimer’s disease is the most common form of dementia.
The researchers found clear differences between the groups. Among women whose sleep remained stable, about 8 percent developed dementia. In the group with worsening nighttime sleep, around 15 percent developed dementia. In the group with increasing sleepiness, about 19 percent developed dementia.
Even after taking into account factors that can affect dementia risk, such as age, race, education, diabetes, and high blood pressure, the researchers found that women with increasing sleepiness had about twice the risk of developing dementia compared with women whose sleep stayed stable.
Interestingly, women who mainly experienced poorer nighttime sleep did not have a significantly higher risk.
Dr. Leng said the findings show that sleep and daily body rhythms can change a great deal even over a relatively short period in very old adults. She believes future studies should examine all aspects of sleep together, including naps, sleep quality, and changes in daily rhythms, to better understand their connection with brain health and dementia risk.
The study also had an important limitation. Most of the participants were white women, which means the findings may not fully apply to people from other racial and ethnic backgrounds. More research involving diverse groups will be needed to confirm the results.
The study was funded by the National Institutes of Health and the National Institute on Aging. Although scientists still have many questions about sleep and dementia, the findings highlight the importance of paying attention to changes in sleeping habits later in life.
Becoming much sleepier during the day may be a sign that deserves closer attention and further discussion with healthcare professionals.
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