Study links weaker internal body clock with higher dementia risk

A study suggests that a person’s internal body clock may influence dementia risk, with weaker circadian rhythms — characterised by greater disruption and irregularity — being associated with a higher likelihood of developing the condition.

Circadian rhythms peaking later in the day, such as post-afternoon, instead of earlier, were linked to a 45 per cent higher risk of dementia.

“Disruptions in circadian rhythms may alter body processes like inflammation, and may interfere with sleep, possibly increasing amyloid plaques linked to dementia, or reducing amyloid clearance from the brain,” study author Wendy Wang, from the University of Texas Southwestern Medical Center, said.

An amyloid plaque is a clump of proteins in the brain, commonly seen in patients of Alzheimer’s disease and contribute to dementia by causing cell death.

The researchers analysed data of over 2,100 older adults with an average age of 79 who did not have dementia at the study’s start. The participants wore chest monitors to measure rest and activity for an average of 12 days.

The study, published in the journal Neurology, followed the participants for three years, during which time, 176 of them were diagnosed with dementia.

A strong circadian rhythm, in which the body clock aligns well with the 24-hour day, sends clear signals for body functions — people tend to follow regular times for sleeping and activity, despite changes in schedule or season, the researchers said.

People with a weak circadian rhythm — more likely to be disrupted by light and schedule changes — are at a higher chance of shifting sleep and activity times with season or schedule changes.

The participants with a low, weaker circadian rhythm had nearly 2.5 times the risk of dementia, compared to those with a high, strong rhythm, the study found.

“Changes in circadian rhythms happen with ageing, and evidence suggests that circadian rhythm disturbances may be a risk factor for neurodegenerative diseases like dementia,” Wang said.

“Our study measured these rest-activity rhythms and found people with weaker and more fragmented rhythms, and people with activity levels that peaked later in the day, had an elevated risk of dementia,” Wang said.

The researchers also found that people who experienced a peak of body clock activity later in the afternoon — 2:15 pm or later — compared to earlier in the afternoon, 1:11 pm-2:14 pm, had a 45 per cent increased risk of dementia.

Seven per cent of those whose circadian rhythms peaked early in the day developed dementia, compared to 10 per cent of those with a high, strong circadian rhythm.

Having a later peak of activity means there could be a difference between the body clock and environmental cues such as later hours and darkness, the team said.