People with trouble sleeping in middle age are more likely to develop symptoms that lead to Alzheimer's disease in later life, according to a new study that revealed an association between the amount and quality of sleep and memory decline. 

Researchers examined sleep patterns of 100 participants between the ages of 45 and 80 who were not affected with dementia, but half of the people tested had a family history of Alzheimer’s disease.

Study author Dr. Yo-El Ju, of Washington University School of Medicine in St. Louis found that people with frequent sleep disruptions and had a habit of lying awake had to greater levels of amyloid plaques, a hallmark sign of Alzheimer’s disease, in their brains. Researchers believe that these plaque deposits that are found in Alzheimer’s patients can begin forming 10 to 15 years before dementia symptoms appear.

Researchers placed a device on participants for two weeks to measure their sleep patterns, and participants were also asked to fill out sleep diaries and questionnaires. The level of amyloid plaques was measured by analyzing participant spinal fluid through positron emission tomography imaging. 

On average participants slept about six-and-a half hours, but spent about eight hour in bed per night.

Ju found that about a quarter of the 100 participants showed abnormal indicators amyloid plaques which were evidence of pre-clinical Alzheimer's disease, and those who woke up more than five times an hour and those who spent less than 85 percent of their time in bed actually sleeping were more likely than other to have the abnormal biomarkers. 

Although researchers noted that the sleep measuring devices may have overestimated the number of awakenings, Ju said that ''people actually do wake briefly quite frequently during a regular night of sleep”.

Previous animal studies have also found that sleep disruptions also accelerated the build-up of amyloid, and researchers from the current study suspect that this may also be true for people.

“Further research is needed to determine why this is happening and whether sleep changes may predict cognitive decline,” Ju said in a statement.

Researchers said that more research consisting of long-term studies and longer follow-ups are needed to accurately determine the association between sleep and Alzheimer’s disease, and although they are still unsure to why the link exists they believe that the current findings lays the groundwork for possible strategies in the prevention or slowing of Alzheimer’s disease by manipulating sleep.

The study is expected to be presented at the annual American Academy of Neurology meeting in April, but some of the findings had been released early.