Study Links Circadian Rhythms to Alzheimer’s Risk

A recent report indicates that circadian rhythms, the internal processes that regulate our sleep-wake cycle, may influence the risk of developing dementia, particularly Alzheimer’s disease. The study discovered that individuals with irregular circadian rhythms, especially those whose activity peaks later in the afternoon, face an increased likelihood of dementia.

Wendy Wang, a researcher at UT Southwestern Medical Center in Dallas, stated, "Changes in circadian rhythms occur with aging, and evidence suggests that disturbances in these rhythms may increase the risk of neurodegenerative diseases like dementia. Our study found that individuals with weaker and more fragmented rhythms, as well as those with later peak activity levels, had a heightened risk of dementia."

Circadian rhythms are controlled by the brain and govern various processes within a 24-hour cycle, including hormone regulation, digestion, and body temperature. Factors such as light exposure, seasonal changes, and work schedules can disrupt these rhythms.

The study involved tracking 2,183 seniors participating in a community heart study, averaging 79 years old, all initially free of dementia. Researchers used heart monitors over 12 days to assess the strength of their circadian rhythms.

Over three years, 176 of the participants developed Alzheimer’s disease or another form of dementia. After accounting for variables like age and heart conditions, those with weaker circadian rhythms were found to be nearly 2.5 times more likely to develop dementia compared to those with strong rhythms.

Additionally, participants whose peak activity occurred at 2:15 p.m. or later experienced a 45 percent higher risk of dementia than those whose peak activity was earlier in the afternoon. Ten percent of the late-afternoon group developed dementia, compared to 7 percent in the earlier group. This suggests that later peak activity may indicate more significant disruptions in the body’s internal clock.

Dr. Wang noted that disturbances in circadian rhythms could affect bodily processes, potentially increasing inflammation and influencing sleep patterns, which are linked to the accumulation of amyloid plaques associated with dementia.

While the study establishes a correlation between circadian rhythm irregularities and increased dementia risk, it does not confirm causation. Published in the journal Neurology, the findings extend previous research that suggests sleep disruptions, such as sleep apnea, elevate Alzheimer’s risk. Also, daytime sleepiness and prolonged afternoon naps have been associated with a greater risk of dementia.

"Future studies should investigate whether interventions targeting circadian rhythms, like light therapy or lifestyle modifications, may help reduce dementia risk," Dr. Wang concluded.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.