A study published in the journal Neurology has found that individuals with irregular internal circadian rhythms may face a heightened risk of developing dementia. Researchers discovered that those whose daily activity peaked later in the day had a 45 percent increased likelihood of dementia compared to others.
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Circadian rhythms govern 24-hour cycles of various bodily functions, including the sleep-wake cycle and hormone release, and are influenced by light exposure. Robust circadian rhythms generally align well with the day-night cycle, helping individuals maintain consistent schedules for sleep and activities.
In contrast, weakened rhythms can lead to irregular sleep patterns, with external factors like light and daily routines often disrupting the body clock. Temporary changes, such as those caused by jet lag or shift work, can negatively impact health when they occur repeatedly.
As people age, their circadian rhythms may become more unstable, with older adults typically experiencing earlier bedtimes and fragmented sleep.
Wendy Wang, the study's author and an assistant professor of epidemiology at UT Southwestern, noted that disturbances in circadian rhythms could be associated with an increased risk of neurodegenerative diseases, including dementia. Wang explained that the research indicated that individuals with more fragmented rhythms or those who were active later in the day showed a greater risk for dementia.
The study assessed over 2,000 participants across the United States, averaging 79 years old and all without dementia at the outset. They wore heart monitors for about two weeks, allowing researchers to analyze their activity and rest patterns and assess rhythm strength. Following the participants for three years, 176 developed dementia.
The participants were grouped based on their rhythm strength. Those in the weakest rhythm category had nearly 2.5 times the risk of developing dementia compared to those with stronger rhythms. Additionally, participants whose activity peaked around 2:15 PM had a 45 percent higher risk of dementia than those who peaked earlier.
In total, approximately 55 million people were affected by dementia globally as of 2019, including around 11 million in Europe. With Europe's aging demographic, that number is expected to rise to 19 million by 2050.
The study's authors aim for their findings to spur further research into how adjusting body clocks can potentially delay or prevent dementia onset. They suggested that interventions like light therapy, melatonin, and lifestyle changes, combined with regular sleep and exercise, may help in maintaining healthy circadian rhythms.