Poor sleep can increase the chances of people at risk for developing Alzheimer's disease.
The scientists performed tests of cerebrospinal fluid in 101 people with a mean age of 63 years who had a family history of Alzheimer's or carried a gene linked to the disease.
Participants who reported poorer sleep quality or suffered from daytime sleepiness had more biological markers for Alzheimer's than those without sleep problems.
Researchers looked for signs of beta-amyloid, groups of toxic brain proteins linked to Alzheimer's disease, and "tau entanglements", nodes of proteins within nerve cells also associated with the disease.
"Previous evidence has shown that sleep can influence the development or progression of Alzheimer's disease in a number of ways," said Dr. Barbara Bendlin of the University of Wisconsin-Madison in the United States.
"For example, disrupted sleep or lack of sleep can lead to amyloid plaque buildup because the brain's cleansing system comes into play during sleep.
"Our study looked not only for amyloid but also for other biological markers in the cerebrospinal fluid."
Not all patients with sleep problems in the study had abnormalities in their cerebrospinal fluid, the researchers said.
For example, there was no relationship between biological markers for Alzheimer's and obstructive sleep apnea.
The results, reported in the journal Neurology, remained the same after taking into account factors such as the use of medications for sleep problems, educational level, depressive symptoms or body mass index (BMI).
Dr. Bendlin added: "It is still unclear whether sleep can affect the development of the disease or whether the disease affects the quality of sleep.
"More research is needed to better define the relationship between sleep and these biomarkers.
"There are already many effective ways to improve sleep.
"It may be possible that early intervention for people at risk for Alzheimer's disease can prevent or delay the onset of the disease."
Dr. Doug Brown, research director of the Alzheimer's Society of Charity, said: "This study adds to the previous evidence that poor quality sleep may be associated with signs of Alzheimer's disease. While it seems that A good quality of sleep can help keep the brain healthy, The exact relationship between sleep and Alzheimer's risk is still unclear.
"While the study highlights that research into any link between sleep and Alzheimer's disease is an avenue worth exploring, it is important to remember that it was a small study that relied on people reporting their own quality Of sleep, which is not the most accurate measurement.
"It remains unknown whether poor sleep is associated with Alzheimer's risk or if people are sleeping poorly due to Alzheimer's disease."
Reporting by PA
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