Weak biological clock is associated with increased risk of dementia

The study involved more than two thousand people with an average age of 79 years, who did not have dementia at the time of the start of observations. For almost two weeks, the participants wore compact sensors on their chests that recorded periods of activity and rest. Their condition was then monitored for an average of three years.

During this time, 176 people were diagnosed with dementia. The analysis showed that people with the weakest circadian rhythms had an almost 2.5-fold higher risk of developing dementia compared to those with stable and pronounced rhythms. In addition, each additional degree of decrease in the amplitude of the rhythm was associated with a further increase in risk.

The researchers paid special attention to the peak time of daytime activity. People whose activity peaked later than usual, in the afternoon, had a significantly higher risk of dementia than those who peaked earlier in the day. The data may indicate a misalignment between the body’s internal clock and external signals such as daylight.

It has been suggested that circadian rhythm disorders may increase inflammation, impair sleep quality, and affect the accumulation or elimination of amyloid plaques, one of the key biological signs of dementia.

The authors emphasize that the study shows a connection, not a direct cause-and-effect relationship. Nevertheless, the results indicate the importance of maintaining a stable daily routine, sleep, and lighting in old age. In the future, experts plan to explore whether measures such as light therapy or lifestyle changes can reduce the risk of developing dementia.

The study also has limitations — in particular, scientists did not have data on sleep disorders such as apnea, which can affect circadian rhythms. Despite this, the work provides grounds to consider the full power of the biological clock as an important marker of brain health in old age.