Researchers found that people with weaker or more irregular internal clocks had a higher risk of developing dementia.
People with less robust and more irregular internal clocks could have an increased risk of developing dementia, according to a new study.
The research, published in Neurology, the medical journal of the American Academy of Neurology, found that disrupted circadian rhythms are associated with higher likelihood of dementia – with a 45 percent increase among people whose daily activity peaked later in the day.
Circadian rhythm is the body’s internal clock that regulates 24-hour cycles of physical, mental, and behavioural changes, such as the sleep-wake cycle, hormone release, digestion, and body temperature. It is guided by the brain and strongly influenced by light exposure.
When circadian rhythms are robust, the body clock aligns well with the 24-hour day and sends clear signals for key body functions. People with stronger rhythms tend to keep regular schedules for sleep and daily activity, even when their schedule or seasons change.
By contrast, when rhythms are weak, changes in light and routine are more likely to throw the body clock off course. People with less stable patterns are more prone to shifting their sleep and activity times.
Temporary alterations such as jet lag and shift work can negatively affect sleep, mood and overall health when repeated or prolonged.
With ageing, circadian rhythms become weaker and more irregular. Older people tend to have earlier bed and wake up times, and more fragmented sleep.
“Changes in circadian rhythms happen with ageing, and evidence suggests that circadian rhythm disturbances may be a risk factor for neurodegenerative diseases like dementia,” said study author Wendy Wang, an assistant professor of epidemiology and internal medicine at UT Southwestern.
“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,” she added.
The research looked at more than 2,000 participants across the United States, with an average age of 79, none of whom had dementia at the start of the study. Participants wore small heart monitors for around two weeks, allowing scientists to track rest and activity patterns and assess the strength of each person’s circadian rhythm.
Researchers then followed the participants for three years during which 176 people developed dementia.
They divided the cohort into three groups, based on rhythm strength measured by the differences between a person’s most and least active periods in a day.
The results showed that those in the weakest rhythm group had nearly 2.5 times the risk of developing dementia as the ones in the stronger rhythm group.
They also observed that people whose activity peaked later in the afternoon – from 2:15 pm – had a 45 percent higher risk of developing dementia than those with an earlier activity peak.
This kind of delayed schedule can cause a mismatch between the body clock and environmental cues, such as later hours and darkness.
Need to tackle dementia
As of 2019, dementia was affecting 55 million people worldwide, and around 11 million people in Europe, according to the European Medicines Agency. With Europe's ageing population, it is estimated the number will reach 19 million in 2050.
The study’s authors said they hope the results can encourage more research to be done on how adjusting one’s body clock could potentially prevent the onset of dementia.
“Our findings also set the stage for future research to assess the potential role of circadian rhythm interventions, such as light therapy, use of melatonin, or lifestyle modifications in preventing dementia,” the researchers wrote.
A regular sleep schedule as well as exercise routines and natural light exposure, especially in the morning, have been proven as effective, non-invasive interventions to help maintain circadian rhythms.
