Interrupted sleep could be an early sign of Alzheimer’s disease, finds new study

In a recent study, scientists at Washington University School of Medicine observed a link between circadian rhythm disruptions (the body clock that determines our sleep/wake cycle) and the risk of an individual developing Alzheimer’s disease.

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Patients with Alzheimer’s disease typically experience disturbances in their sleep/wake cycles, caused by alterations to their internal body clocks.

In the current study, researchers observed the disruptions to circadian rhythm patterns in much younger people, whose memories are intact but whose brain scans show early, preclinical evidence of Alzheimer's disease.

The study, which was published in the journal JAMA Neurology, could aid doctors to identify people at risk of Alzheimer’s much earlier on than at present.

Since Alzheimer's could affect the brain 15 to 20 years before the emergence of its clinical symptoms, correcting sleep patterns in the pre-clinical stages could slow the disease down.

It wasn't that the people in the study were sleep-deprived. But their sleep tended to be fragmented. Sleeping for eight hours at night is very different from getting eight hours of sleep in one-hour increments during daytime naps."

Erik S. Musiek, MD, PhD, First Author and Assistant Professor of Neurology at Washington University.

The research team tracked circadian rhythms in 189 adults who showed no symptoms of any cognitive impairment and had an average age of 66.

Pre-clinical features of Alzheimer’s were assessed by positron emission tomography (PET) scans which showed the presence amyloid plaques in their brains, or cerebrospinal fluid sampling, which was analyzed for Alzheimer's-related proteins.

Out of 189 participants, 139 had no evidence of amyloid proteins that indicate preclinical Alzheimer's. Most had normal sleep/wake cycles; however, several had circadian disruptions that were associated with advanced age, sleep apnea or other causes.

The rest of the participants had either abnormal cerebrospinal fluid or abnormal brain scans. All 50 of these individuals showed significant disruptions to their circadian rhythms, determined by their rest time during the night and their activeness during the day.

Disruptions in the sleep/wake cycle prevailed even after the researchers statistically controlled for sleep apnea, age and other factors.

The study participants from Washington University's Knight Alzheimer's Disease Research Center were instructed to wear devices that are similar to exercise trackers for one to two weeks. They were also asked to complete a detailed sleep diary every morning.

The research team tracked and analyzed the day and night activities of participants throughout 24-hour periods.

They discovered that people affected with preclinical Alzheimer's disease have more disruptions in their circadian activity patterns, with increased periods of sleep or inactivity during the day and more periods of activity at night.

The scientists also carried out a separate study in mice, which showed similar circadian disruptions that accelerated the development of amyloid plaques in the brain, a process linked to Alzheimer’s disease.

The findings support the work of Dr Musiek, who used mouse models to show that amyloid levels tend to fluctuate in predictable ways during the day and night. Plaques tended to decrease during sleep, and increase when sleep is disrupted or when individuals do not get enough deep sleep.

At the very least, these disruptions in circadian rhythms may serve as a biomarker for preclinical disease. We want to bring back these subjects in the future to learn more about whether their sleep and circadian rhythm problems lead to increased Alzheimer's risk or whether the Alzheimer's disease brain changes cause sleep/wake cycle and circadian problems."

Dr Yo-El Ju, MD, Senior Author of the study