Within the body, a 24-hour rhythm, often known as the circadian rhythm, is quietly synchronized as we sleep, wake, eat and get better. This internal timing system helps the organs and hormones to work in harmony. When it’s disrupted, the results can extend beyond poor sleep, with growing evidence suggesting long-term mental health consequences.
A big 2025 study of greater than 2,000 individuals with a mean age of 79 found that those with strong circadian rhythms had about half the chance of developing dementia. Circadian rhythms regulate each day processes including sleep timing, hormone release, heart rate and body temperature.
Over three years of follow-up, dementia developed in 7% of participants with body clocks, as measured using a heart rate monitor, compared with 10% of those whose rhythms remained regular.
Disrupted circadian rhythms are sometimes related to impoverishment sleep. For a long time, poor sleep has been suspected to contribute to each dementia and heart disease, which share several underlying risk aspects. i 2025 studyworse Heart health and hypertension, each commonly related to sleep disturbances, were accounted for within the evaluation. Sleep apnea, nonetheless, was not.
Sleep apnea is a typical condition by which respiratory stops and starts repeatedly during sleep, reducing oxygen supply to the brain and raising blood pressure. Its relationship to dementia stays debated, largely because sleep apnea is more common in individuals who have already got it. Risk factors for dementia are established Such as obesity, diabetes, smoking and alcohol abuse. This overlap makes it difficult to find out whether sleep deprivation itself increases the chance of dementia or whether it reflects broader metabolic and cardiovascular vulnerability.
This Review suggested that ameliorating fatigue-related physical inactivity with disrupted sleep could also be a promising approach. Increased activity can reduce obesity, improve sleep quality and support brain cell health, potentially reducing the chance of dementia through several pathways at the identical time.
Other explanations may help make clear links between disrupted circadian rhythms and dementia. One involves the immune system, which is affected by circadian rhythms in addition to sleep and plays a job in each heart disease and neurodegeneration. There is one other The theory that Sleep supports the removal of toxic proteins from the brain, including the amyloid plaques that characterize Alzheimer’s disease, through a waste clearance system that appears to be more lively during sleep.
Although this clearance hypothesis is widely debated, evidence has been found. Some animal studies, incl They are in micehas been shown to diminish moderately than increase toxin clearance during sleep. Animal results must be interpreted with caution, sleep patterns in rats is quite different In humans, especially in later life.
The Lancet Commission update Dementia prevention concluded that sleeping for longer or shorter periods is unlikely to be a real independent risk factor for dementia. One reason for this conclusion is that evidence from real-world sleep disturbances doesn’t clearly point to sleep duration because the primary driver of risk. Shift work though is associated with Dementia Risks, Studies Increase Don’t show permanently Night shift employees are at higher risk than day shift employees. If sleep disturbances alone were responsible, night shifts could be expected to be at greater risk.
This suggests that circadian disruption could also be vital independently of sleep duration. However, shift work can also be related to unhealthiness Lifestyle patternsincluding poor food regimen, smoking, alcohol use and variable physical activity. Chronic stress, lack of routine, hormonal disruption, increased blood pressure, reduced leisure opportunities and social isolation also cluster around shift work. Each of those aspects has been independently linked to dementia, heart disease and poor sleep, complicating efforts to isolate the results of circadian disruption alone.
The Lancet authors also reasoned that if amyloid clearance occurs in humans, it likely occurs through the first two hours of sleep, when deep sleep is most outstanding. Deep sleep is preserved even when the entire sleep duration falls below seven hours. They due to this fact suggest that fragmented sleep and disrupted circadian rhythms could also be early consequences of dementia-related brain changes moderately than causes. Toxic plaque can accumulate in brain regions that regulate sleep and wakefulness long before memory problems turn out to be apparent.
So should sleep be eliminated in dementia prevention? The Lancet’s advice was not to limit sleep. Evidence linking prolonged sleep, defined as greater than eight hours, to dementia risk was not supported when the broader data were considered.
A recent trial tested a personalised program combined with several methods, akin to light exposure, sleep schedules, daytime activity and caregiver support, to enhance sleep in individuals with dementia. After eight months, sleep improved within the intervention group, although sleep also improved with usual care. The overall effect was small to moderate, and there was no improvement in dementia-related behaviors or overall health. These methods may profit caregivers by supporting routines, but their impact appears to be limited for individuals with dementia.
Severe and chronic sleep deprivation, especially lack of deep sleep and REM sleep, Can corrupt memory. Whether long-term disruption of restorative sleep increases the chance of dementia later in life, and whether treating sleep problems can prevent dementia, is uncertain.
Because improving sleep is usually seen as a possible prevention strategy, medications used to treat insomnia also deserve scrutiny. Dangerous drugs like benzodiazepines are on the rise Risk of dementiain addition to daytime drowsiness, falls and accidents. Meltonwhile utilized by many, has not shown consistent advantages for improving sleep in adults.
That said, there are evidence-based methods Improve sleep and support healthy circadian rhythms. Regular moderates exercisearound half-hour a day, especially outdoors and before noon, is only. As a bonus, physical activity can also be certainly one of the strongest protective aspects against heart disease Dementia. So wrap up warm and go.