New US research has found sleep problems in healthy individuals could be an indicator that they may go on to develop Alzheimer's disease later in life.
Carried out by the University of Wisconsin-Madison, the study adds to existing research which suggests sleep quality could be linked with the disease.
"Previous evidence has shown that sleep may influence the development or progression of Alzheimer's disease in various ways," explained study author Barbara B. Bendlin, PhD, "For example, disrupted sleep or lack of sleep may lead to amyloid plaque buildup because the brain's clearance system kicks into action during sleep. Our study looked not only for amyloid but for other biological markers in the spinal fluid as well."
Amyloid is a protein that can fold and form into plaques in the brain, while another protein, Tau, forms into tangles. Both plaques and tangles are found in the brains of people with Alzheimer's disease.
For the new research the team recruited 101 people with an average age of 63 who had normal thinking and memory skills, but who were considered at risk of developing Alzheimer's.
Participants provided the team with information about their sleep quality as well as spinal fluid samples, which where then tested for biological markers of Alzheimer's disease, including signs of amyloid, tau and brain cell damage and inflammation.
The results, published in the online issue of Neurology, the medical journal of the American Academy of Neurology, showed that those who reported worse sleep quality, more sleep problems and daytime sleepiness had more biological markers for Alzheimer's disease in their spinal fluid than people who did not have sleep problems.
The results still held true even after researchers had taken into account other factors such as medications for sleep disorders, education, depression symptoms or body mass index.
However, not everyone who had a sleep problem had biological markers in their spinal fluid, with the team finding no link for the sleep problem of obstructive sleep apnea.
Bendlin did note that, "It's still unclear if sleep may affect the development of the disease or if the disease affects the quality of sleep. More research is needed to further define the relationship between sleep and these biomarkers."
However, she also added, "There are already many effective ways to improve sleep. It may be possible that early intervention for people at risk of Alzheimer's disease may prevent or delay the onset of the disease."