New York, Jul 6 (PTI): Poor, disrupted sleep may indicate the risk of developing Alzheimer's disease in people who are otherwise healthy, a study warns.

Researchers from University of Wisconsin-Madison in the US found that people 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.

Those biological markers included signs of the proteins amyloid and tau and brain cell damage and inflammation.

"It's important to identify modifiable risk factors for Alzheimer's given that estimates suggest that delaying the onset of Alzheimer's disease in people by a mere five years could reduce the number of cases we see in the next 30 years by 5.7 million," said Barbara B Bendlin, PhD student at University of Wisconsin-Madison.

While some of these relationships were strong when looking at everyone as a group, not everyone with sleep problems has abnormalities in their spinal fluid.

There was no link between biological markers in the spinal fluid and obstructive sleep apnea, researchers said.

"It is still unclear if sleep may affect the development of the disease or if the disease affects the quality of sleep," Bendlin said.

Researchers recruited 101 people with an average age of 63 years who had normal thinking and memory skills but who were considered at risk of developing Alzheimer's. They either had a parent with the disease or were a carrier of a gene that increases the risk for Alzheimer's disease called apolipoprotein E or APOE.

Participants were surveyed about sleep quality. They also provided spinal fluid samples that were tested for biological markers of Alzheimer's disease. The study was published in the journal Neurology.