Disrupted sleep could be an early indicator of Alzheimer’s disease, even before any memory loss or other symptoms appear. Although sleep problems are common for people diagnosed with the disease, a new study is among the first to link early dementia and sleep problems in humans.
The study involved 145 participants between 45 and 75 years old. At the beginning of the study none of them had any sign of cognitive issues. However based on the analysis of their spinal fluid, 1/3 were likely to have amyloid plaques in the brain, and were thus considered as preclinical Alzheimer’s.
All participants kept sleep diaries for 2 weeks. They noted when they went to bed, when they woke up, when they napped, etc. During these 2 weeks they also wore wrist sensors to detect movements, both while awake and asleep. The sensors allowed the researchers to objectively evaluate sleep efficiency, that is the percentage of time in bed spent asleep.
Results showed that people with preclinical Alzheimer’s had worse sleep efficiency than those without: They spent 80.4% of the time in bed asleep compared to 83.7%. This was true in spite of the fact that the quantity of sleep (total sleep time) was not different between the two groups. People with preclinical Alzheimer’s also took more frequent naps (3 or more times a week).
The least efficient sleepers (people whose sleep efficiency was lower than 75%) turned out to be five times more likely to have preclinical Alzheimer’s.
In sum the study showed that the presence of amyloid in the preclinical stage of Alzheimer’s is associated with disrupted sleep patterns, that is worse sleep quality but not necessarily diminished sleep quantity.
Of note, it is not clear what the direction of the association is. Does disrupted sleep promote the accumulation of amyloid in the brain or does Alzheimer’s disease lead to disrupted sleep? There is no answer to this question yet. However, knowing of such an association is important as it could be used as an easily detectable sign of early Alzheimer’s. This may be useful when treatment become available. Sleep patterns could even be used to measure the efficacy of treatment.
References: Ju, Y.-E., S. et al. (2013). Sleep Quality and Preclinical Alzheimer Disease. JAMA Neurol. 2013;():1-7. doi:10.1001/jamaneurol.2013.2334.