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A new study indicates that disruptions in the body’s internal clock, or circadian rhythm, may significantly raise the risk of developing dementia. Researchers found that older adults with weaker and more irregular circadian patterns were more likely to be diagnosed with the condition over time. The study suggests that when daily activity rhythms peak later in the day—particularly after mid-afternoon rather than earlier hours—the risk of dementia increases sharply. Individuals whose activity levels peaked later were found to have about a 45 per cent higher likelihood of developing dementia compared to those with earlier peaks. According to Wendy Wang, the study’s lead author from the University of Texas Southwestern Medical Center, disrupted circadian rhythms may affect key biological processes. “Such disruptions can influence inflammation and sleep, potentially leading to increased buildup of amyloid plaques in the brain or reducing the brain’s ability to clear them,” she explained. Amyloid plaques are clusters of protein fragments commonly associated with Alzheimer’s disease and are known to damage brain cells, contributing to cognitive decline and dementia. The researchers examined data from more than 2,100 adults with an average age of 79, none of whom had dementia at the beginning of the study. Participants wore chest-mounted devices that tracked their rest and activity patterns for nearly two weeks on average. They were then monitored over a three-year period. During the follow-up, 176 participants were diagnosed with dementia. The findings, published in the journal Neurology, revealed that those with weaker circadian rhythms—marked by irregular sleep and activity cycles—had nearly two-and-a-half times the dementia risk compared to individuals with strong, stable rhythms. A well-regulated circadian rhythm typically aligns closely with the 24-hour day, helping maintain consistent sleep and activity schedules regardless of seasonal or routine changes. In contrast, weaker rhythms are more susceptible to disruptions from light exposure or schedule shifts, often resulting in fluctuating sleep patterns. The study also highlighted timing differences in daily activity. Participants whose peak activity occurred after 2:15 pm faced a significantly higher dementia risk compared to those whose activity peaked earlier in the afternoon. Researchers noted that a delayed activity peak may reflect a mismatch between the body’s internal clock and external environmental cues such as daylight and darkness. Wang added that while changes in circadian rhythms are a natural part of ageing, growing evidence suggests these disruptions may play a role in neurodegenerative diseases. “Our findings show that fragmented rhythms and delayed activity patterns are associated with a higher risk of dementia,” she said. The research underscores the potential importance of maintaining regular sleep-wake cycles and daily routines as people age, though further studies are needed to determine whether improving circadian health can help reduce dementia risk. Source: PTI