In the last few years, several studies have found evidence that disrupted sleep patterns could be an important risk factor in the onset of Alzheimer’s disease and other forms of dementia. Now, researchers have found more indications that bad sleep begins much earlier than Alzheimer’s.

The study, published in JAMA Neurology, highlights changes in the circadian rhythm of people likely to develop the condition. This was before any indication of memory loss was seen in the patients. The study was conducted at the Washington University School of Medicine in St. Louis.

“In this new study, we found that people with preclinical Alzheimer’s disease had more fragmentation in their circadian activity patterns, with more periods of inactivity or sleep during the day and more periods of activity at night,” said senior author Professor Yo-EL Ju in a statement.  

The researchers tracked the sleep patterns of 189 adults with an average age of 66 and used different scanning techniques to establish the presence of Alzheimer’s-related proteins or plaques. Of the participants, 139 had no indication of Alzheimer’s disease and most of them had normal sleep/wake cycles. The disruptions of the remaining were linked to other causes, such as advanced age or sleep apnea.

The 50 patients that had an indication of the disease all experienced significant disruptions of their internal body clocks. The finding persisted even when the researchers tried to account for other disrupting factors like in the healthy subset.

“It wasn’t that the people in the study were sleep-deprived,” explained first author Professor Erik S. Musiek. “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.”

The researchers also produced a separate study in mice, published in the Journal of Experimental Medicine, where they showed that disruptions to one's regular sleep patterns led to an increase in the protein plaques, which are suspected to be one of the causes of Alzheimer’s.

“Over two months, mice with disrupted circadian rhythms developed considerably more amyloid plaques than mice with normal rhythms,” Musiek said. “The mice also had changes in the normal, daily rhythms of amyloid protein in the brain. It’s the first data demonstrating that the disruption of circadian rhythms could be accelerating the deposition of plaques.”

Alzheimer’s disease affects over 50 million people worldwide. It is the most common form of dementia.