A device worn on the wrist may help to detect the early warning signs of Alzheimer's disease before it leads to serious cognitive decline, a study has suggested.
Around six million US adults live with Alzheimer's. Although there is no cure for the progressive disease, early and accurate diagnosis allows people to access treatments for their symptoms, as well as adequate support and care.
Watch-like devices called actigraphs monitor the daily activity patterns of their wearers. In the new study, led by scientists at the Johns Hopkins Bloomberg School of Public Health, researchers analyzed the movement data of 82 cognitively healthy older adults—with an average age of 76—who were participants in a long-running study of aging.
Each participant wore the watch-like device continuously for a week.
Each subject was also given a PET scan. This revealed that 25 of the adults had a build-up of the protein amyloid beta in their brains—a key feature of Alzheimer's disease.
The actigraphs revealed significant differences in activity patterns between the people who had amyloid build-up and those who did not. Specifically, the amyloid-positive adults tended to be more active in the afternoon than those who were amyloid-negative.
The findings support those of an earlier study, suggesting that actigraphs could be useful in detecting the early signs of Alzheimer's before significant cognitive impairment occurs.
The researchers suggest the devices could be one day be worn by people to track their sleep and waking activity. Those with abnormal patterns could then consult their doctors for more in-depth Alzheimer's screening.
"We need to replicate these findings in larger studies, but it is interesting that we've now seen a similar difference between amyloid-positive and amyloid-negative older adults in two independent studies," said Adam Spira, a study author and professor in the department of Mental Health at the Bloomberg School, in a press release.
It's not known exactly why amyloid build-up would lead to different activity patterns at specific times of day. However, there is a well-known phenomenon among individuals with Alzheimer's disease called 'sundowning', in which agitation increases in the afternoon and early evening, which may be caused by poor sleep.
Abnormal sleep patterns are thought to be potential early indicators of Alzheimer's disease. This may be because Alzheimer's-related brain changes can affect a person's circadian rhythm, which dictates how sleepy or awake they are. However, sleep loss can also contribute to the amyloid build-up, making it a vicious cycle.
"Sundowning is something that we hear a lot about anecdotally, but we don't understand very well. Some people have suggested that transitions during afternoon shift changes in nursing homes may somehow contribute," Spira told Newsweek.
"Others believe that lower levels of light in the afternoon increase confusion among people with dementia who might also have vision loss. Sleep and circadian researchers are interested in light because it plays a major role in synchronizing our behavior with the dark/light cycle.
"It is tempting to think that the change in light at that time of day may play a role by affecting the circadian timing system, which is governed by the master clock in our brains and clocks throughout our cells."
Alternatively, sundowning may have less to do with the change in light in the afternoon and more to do with people becoming less alert because they haven't received a good dose of light in the morning.
"Studies of people living in nursing homes have shown that they tend to be exposed to lower levels of light throughout the day. Clearly, more research in this area is needed," added Spira.
In the new study, the higher afternoon activity may be a sign of 'preclinical sundowning', according to the researchers. However, he added, it's important to note that the findings represent averages among a small sample of older people over a short period of time.
Crucially, it's not possible to predict whether an individual will develop amyloid plaques based on the timing of their activity. Therefore, people shouldn't be worried if they are particularly active in the afternoon.
Although the development of Alzheimer's disease is still not fully understood, research suggests amyloid plaques and tangles begin to accumulate in the brain one or two decades before someone is diagnosed. Treatments to slow the progression of the disease are more effective if given earlier.
"Eventually, the hope is that there will be treatments available that meaningfully prevent or even reverse the progression of Alzheimer's disease," said Spira.
"People in the field tend to think that intervening early, before the disease has a chance to destroy too many neurons, will lead to better results."
Detecting Alzheimer's disease earlier also helps to identify people who might be good candidates for randomized trials of experimental treatments for Alzheimer's disease.
"They could also help clinicians to increase monitoring of patients who appear to be at high risk, and to provide families with resources that can help them care for their loved ones as the disease progresses," added Spira.
The full findings of the study were published in the journal SLEEP.
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Update 03/19/24, 8:05 a.m ET: This article was updated with additional comments from Adam Spira.
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