Sleep and body rhythm disorders lead to dementia

The study presents sleep not just as a state of rest, but as a highly organized biological process. During this time, the brain coordinates chemical reactions, the pulsation of blood vessels, and the flow of cerebrospinal fluid.

In 2012, the Nedergaard Laboratory discovered the glymphatic system, a network of channels that circulate cerebrospinal fluid around blood vessels to eliminate metabolic waste. This system operates most intensively during sleep, acting as a nighttime cleaning mechanism. Research shows that it is the glymphatic system that helps remove the proteins amyloid beta and tau from the brain, the accumulation of which is a sign of Alzheimer’s disease and other types of dementia.

During the phase of slow-wave sleep (non—REM), neuromodulators – brain chemicals responsible for mood and attention — go into a state of synchronous oscillations, repeated about once a minute. These rhythms control not only the activity of neurons, but also breathing, heart rate, movement of blood and cerebrospinal fluid.

These slow rhythms stimulate what is known as vasomotion, the rhythmic changes in the diameter of blood vessels that occur independently of the heartbeat. It is these vascular pulsations that push cerebrospinal fluid through the brain tissue, washing away toxic deposits.

Nødregaard argues that aging, stress, mental illness, and cardiovascular disorders disrupt these subtle biological rhythms. When natural cleansing is disrupted, the brain loses its ability to effectively remove toxic proteins, which creates a favorable environment for the development of neurodegenerative diseases. Thus, many factors that increase the risk of dementia may be linked to the brain’s ability to clean itself during sleep.

The authors of the article point to heart rate variability (small changes in the intervals between heartbeats) as a potential biomarker of brain health. It has been found that fluctuations in heart rate during sleep are closely associated with the rhythms of neuromodulators in the brain.

This discovery allows for the use of non-invasive monitoring methods, such as regular fitness bracelets, to assess the effectiveness of nighttime brain cleaning. In the future, this could help identify individuals at an increased risk of cognitive impairment before the onset of clinical symptoms, enabling early preventive measures.