What Your Wrist Tells You About Your Dementia Risk

What if your daily routine, specifically when you move, could silently reveal early warning signs of Alzheimer’s? It may sound like science fiction, but new research using wearable activity trackers reveals surprising links between subtle shifts in your movement patterns and the presence of a hallmark brain protein tied to the disease. How your body behaves in the afternoon—or even while you sleep—could be trying to tell you something critical about your brain’s future.

Key Takeaways

• Afternoon Activity Patterns May Signal Risk: Older adults with brain amyloid buildup showed distinct patterns of higher activity in the early morning and afternoon, along with more variability during typically quiet nighttime hours.

• “Preclinical Sundowning” Hypothesis: Researchers speculate that elevated afternoon movement could reflect an early version of “sundowning,” a known behavioral symptom in Alzheimer’s patients.

• Actigraphs Show Promise in Early Detection: If further validated, wearable devices could become tools to help detect Alzheimer’s risk before cognitive symptoms appear.

This Unexpected Activity Pattern May Signal Alzheimer’s 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. 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 Johns 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 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. 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.

Summary

A pair of studies from Johns Hopkins University suggests that subtle differences in daily activity, measured by wearable actigraphs, could be early indicators of Alzheimer’s risk. Participants with amyloid buildup in their brains had distinct movement patterns, such as higher activity in the morning and afternoon, and more variability at night. These changes may relate to “preclinical sundowning,” a behavior seen in later-stage Alzheimer’s. While these findings are still preliminary, they raise the possibility that wearable technology could one day play a role in early detection. However, researchers caution against overinterpreting current data and emphasize the protective role of regular exercise and consistent sleep for long-term brain health.

Frequently Asked Questions

What is an actigraph, and how does it work?

An actigraph is a wrist-worn device that tracks movement to monitor activity levels, often used in sleep and behavioral research.<

How does activity pattern relate to Alzheimer’s disease?

Studies show that people with amyloid buildup in the brain tend to have altered activity patterns, particularly more afternoon activity and nighttime variability.

What is "preclinical sundowning"?

It’s a term used to describe the possibility that agitation and activity shifts seen in Alzheimer’s patients may start subtly years before diagnosis.

Should I be worried if I’m more active in the afternoon?

No—researchers stress that these findings are averages in small samples. Many factors affect daily activity patterns.

How can I lower my Alzheimer’s risk now?

Regular physical activity, a healthy sleep routine, and maintaining overall wellness are proven ways to reduce dementia risk.