What Your Wrist Tells You About Your Dementia Risk

Most of us have a daily pattern, carrying out certain activities regularly and resting at other times. We don’t think much about this pattern, but perhaps we should.

That’s because the times of day we’re active and for how long could provide important clues as to who will suffer from Alzheimer’s in the future. It may sound unlikely, but a new study of people wearing an activity-monitoring wrist device called an actigraph suggests this. The device accurately measures body movement, and what researchers are finding is pretty amazing.

Actigraphs and Alzheimer’s Risk

Actigraph mechanical sensors were first introduced in the 1950s, and their ongoing development—now incorporating digital wrist-worn technology—has enhanced their accuracy and reliability for measuring body movement.

The actigraph is mostly used by sleep medicine clinicians. In fact, we recently reported on research that showed how people wearing actigraphs and were documented to take long daytime naps are at a higher risk for Alzheimer’s disease.

Most recently, researchers at John’s Hopkins University put the actigraph to work in a novel way. They used actigraphs in two studies to see whether activity patterns in older adults differ between those with a buildup of Alzheimer’s-linked amyloid in the brain and those without.

More Active in The Afternoon

Their first study looked at data on 59 cognitively healthy seniors. Brain scan data found 26 who tested positive for amyloid and 33 who showed no signs of the rogue proteins on the scan.

After wearing an actigraph for about a week and using a sensitive statistical technique called FOSR (function-on-scalar regression), they found that amyloid positive participants had lower activity levels in the late night through the early morning and higher levels in the early morning and from midday through late afternoon than those without amyloid.

Specifically, the amyloid positive participants had:

• Lower activity levels from 11:30 p.m. to 3:00 a.m.
• Higher activity levels from 4:30 a.m. to 8:30 a.m.
• Higher activity levels from 12:30 p.m. to 5:30 p.m.

The amyloid group also had higher variability in activity across the study days—in other words, their activity levels were up and down. This occurred during the following hours:

• 12:30 p.m. to 5:30 p.m.
• 9:30 p.m. to 1:00 a.m.
• 4:30 a.m. to 8:30 a.m.1

Interestingly, some of the activity variability occurred during the nighttime hours when people mostly sleep. We recently reported on research showing that inconsistent sleep patterns are linked to a 53 percent increased risk of developing dementia, with irregular sleep contributing to deficits in cognitive functions and impairing the glymphatic system’s efficiency in brain waste clearance.

The differences in the activity levels between those with the Alzheimer’s biomarker and those without were clear, but researchers couldn’t draw any conclusion from a single small study, so they followed this up with another scientific investigation a few years later.

Lower Afternoon Variability

For their new study, researchers tracked the activity levels of 82 community-dwelling men and women with an average age of 76. Of the group, 25 tested positive for amyloid and 57 tested negative.

As in the first study, all wore an actigraph 24 hours a day for one week. This time the researchers found the amyloid-positive participants had higher average activity levels from 1:00 to 3:30 p.m., and less day-to-day variability in activity from 1:30 to 4:00 p.m. and 7:30 to 10:30 p.m.2

While there are differences between the two studies, the new study's findings of higher afternoon activity and lower afternoon variability among the amyloid positive echoed the investigators’ prior findings.

Activity Differences Triggered by Sundowning

The scientists couldn’t say why amyloid buildup would trigger differences in activity patterns during these times of day but suggested it could be related to a well-known phenomenon among Alzheimer’s patients called “sundowning”, whereby agitation increases in the afternoon and early evening.

Adam Spira, who led both studies, said, “it is interesting that we’ve now seen a similar difference between amyloid-positive and amyloid-negative older adults in two independent studies. It’s conceivable that the higher afternoon activity we observed is a signal of ‘preclinical sundowning’.”

“At the same time, it’s important to note that these findings represent averages among a small sample of older people over a short period of time. We can’t predict whether an individual will develop amyloid plaques based on the timing of their activity. So, it would be premature for older people to be concerned because their fitness trackers say they are particularly active in the afternoon, for example.”3

Professor Spira and his colleagues hope that if these findings can be replicated in larger studies, then actigraphs could be a future tool to help detect Alzheimer’s at its very earliest stages before marked cognitive impairment sets in.

Our Takeaway

The findings are certainly worth more study, but we wouldn’t get anxious over the activity levels—or lack thereof— of you or a loved one just yet. Meanwhile, another form of activity is predictive of maintaining a sharp memory and being free from dementia. That’s regular exercise.

Higher levels of physical activity are linked to a lower risk of developing dementia, including Alzheimer's disease. The studies to date have found that as physical activity increased from inactive to insufficiently active, active, and highly active levels, there was a progressively lower risk of dementia.4

One large study showed the risk of dementia decreased steeply with increasing physical activity up to around 1,000 to 1,500 minutes/week, after which the risk plateaued. Even light physical activity levels of 1-299 minutes/week were associated with reduced dementia risk compared to being completely sedentary.5

Sleep, as we mentioned earlier, is also important. Maintaining a regular sleep-wake schedule and a healthy circadian rhythm is essential for cognitive health, potentially reducing the onset of Alzheimer’s pathology and improving overall well-being.