Poor Sleep May Be Early Signal of Alzheimer’s Disease

In lab animal studies, disrupted sleep has been shown to cause a build-up in beta-amyloid markers characteristic of Alzheimer's Disease. Washington University School of Medicine (Missouri, USA), researchers report that signs of these beta-amyloid plaques ts can be detected in cognitively normal people who experience frequent awakenings and a habit of lying awake.  Yo-El Ju and colleagues analyzed data collected in the Adult Children Study, in which half the subjects have a family history of Alzheimer's. For this analysis, 100 participants, ages 45 to 80 years, were given standardized assessments and shown to be cognitively normal. Participants wore an actigraph for 14 days to measure sleep in an objective fashion; sleep diaries and questionnaires were used to gather subjective measures. The researchers also measured levels of amyloid beta-42 in cerebrospinal fluid and looked for increased retention of Pittsburgh compound B during amyloid imaging by positron emission tomography -- 25% of participants had preclinical signs of Alzheimer's. On average, participants spent about eight hours in bed, as measured by both actigraph results and subjective reports, but average sleep time on the actigraph was 6.5 hours because of brief awakenings during the night. Those who woke up more than five times an hour were more likely to have abnormal biomarkers indicating amyloid pathology. And more of those with low sleep efficiency – defined as sleep time divided by time in bed of less than 85% – had such signs compared with those with high sleep efficiency. Further studies to establish correlation of causality are needed, to establish the role of disrupted sleep as a factor in Alzheimer's Disease.