A new study, conducted by researchers at the Mayo Clinic and published this week in the academic journal JAMA Neurology, is the latest to link daytime drowsiness with early signs of Alzheimer's disease, a condition that is projected to affect 14 million people by 2050, according to Atlanta-based Centers for Disease Control and Prevention.\
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Researchers at the Mayo Clinic followed nearly 3,000 elderly subjects participating in an ongoing study on aging over the course of seven years.
Of the large group, 283 individuals over 70 without dementia were selected to answer survey questions about their sleep habits and also agreed to receive several brain scans that examined amyloid protein deposits in their brains.
Those amyloid protein deposits (or plaques) are considered sure signs of the disease. According to a study that found a link between messy sleep-wake cycles and Alzheimer’s, amyloid levels typically decrease during sleep and increase when sleep is disrupted or when people don’t get enough good sleep.
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"In our study, we wanted to know if excessive daytime sleepiness causes an increase of amyloid over time in people without dementia," study author Prashanthi Vemuri, a research faculty member at the Mayo Clinic, told CNN.
"And the answer was yes," she said.
According to the study results, the individuals who experienced the most drowsiness during the day also had higher levels of amyloid buildup. The increase in amyloid occurred at especially high rates in areas of the brain associated with emotion, memory retrieval and behavior.
"I would hope that people understand that good sleep habits are important to have a healthy brain, since it can prevent amyloid, which is one of the primary proteins underlying Alzheimer's disease," Vemuri told TIME.
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Although the study showed a connection between daytime sleepiness and amyloid, it remains unclear whether the buildup causes sleep disruptions or whether poor sleep leads to an increase in the brain plaque. Researchers are further examining whether or not improving an individual's sleep habits can curb the increase of amyloid.
Some doctors however, have already decided to incorporate the study's results into their analysis of patients.
"While further research is necessary, this study adds a new question that doctors can ask patients to assess risk and potentially intervene, Dr. Richard Isaacson, Director of the Alzheimer's Prevention Clinic at Weill Cornell Medicine and New York-Presbyterian, who was not involved with the research, explained.
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"The findings will change the way I care for patients," he said. "I will now proactively ask about excessive daytime sleepiness as one of the many potentially modifiable risk factors for the disease."
Other experts have expressed their excitement over the study's findings.
"Importantly, it is the first longitudinal study of the relationship between sleep and Alzheimer's Disease in the pre-clinical stage, meaning before any cognitive changes appear," Dr. Yo-El Ju, a neurologist at the Washington University School of Medicine, said.
"This finding is important because it means we could potentially treat sleep problems to reduce risk of [Alzheimer's disease] years down the road."
Inadequate sleep is a nationwide issue, with a third of U.S. adults reporting that they regularly get less than the recommended amount of sleep, according to the Centers of Disease Control and Prevention. As many as 50 to 70 million Americans also struggle with sleep disorders.
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Previous scientific research has already shown potential links between poor sleep and dementia. For example, a 2017 study showed that individuals who get less REM, or dream stage, sleep could face a greater risk of dementia.
Another study published last year looked at subjects with increased risk factors for Alzheimer's. The research showed that worse sleep may contribute to the accumulation of Alzheimer's-related proteins in the brain. Even sleeping badly for one night can increase the buildup of amyloid in the brain, according to yet another study published last year.
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"Overall, these studies confirm the relationship between early Alzheimer's disease and sleep disturbance," Ju pointed out.
"They expand – in terms of both time and symptoms – the window in which sleep-wake problems can be assessed for and treated, with the hope of reducing the risk of dementia due to Alzheimer's disease."
Read the full Mayo Clinic study at jamanetwork.com.
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