He dream slow wavesalso known as deep sleep or stage number 3 of non-REM sleep, constitutes the deepest and most restorative phase of night rest. At this stage, mental electrical signals are characterized by high-amplitude, low-frequency delta waves, which allows it to be distinguished from other moments of rest.

According to Science DirectDuring this period, eye movements disappear and muscle tone is significantly reduced, making it difficult for people to wake up. In healthy adults, represents between 15 and 25% of the total rest time. It is mainly distinguished by its high ability to restore brain functions.

This is an essential moment for consolidating memory and optimizing neuronal connections, in addition to playing a key role in metabolic cleansing of the brain. According to the specialist Txomin Navajas Carasa, in dialogue with Hospital, allows the removal of waste such as beta amyloid and tau proteinscompounds related to the development of Alzheimer’s.

Slow wave sleep is part of the ultradian rhythm, repeating in cycles throughout the night. Science Direct points out that this type is characterized by a decrease in the activity of neurotransmitters such as acetylcholine and serotonin, which facilitates the appearance of the slow oscillations typical of this stage. The alternation between phases of neuronal activation and rest generates the high amplitude waves observed in the electroencephalogram.

During deep sleep, the brain also activates purification mechanismsknown as the glymphatic system, which increase interstitial space and promote the elimination of metabolic toxins. cnn highlights that at this stage potentially harmful substances are eliminated, such as the beta-amyloid protein, contributing to protection against neurodegenerative diseases.

How it works on brain health

This phase also acts as essential regulator of brain processes. Science Direct describes that mental activity is organized in slow and synchronized oscillatory patterns that alternate periods of neuronal activation and rest. These oscillations, originating mainly from the cortex, propagate in waves through the brain and are accompanied by a general decrease in neurotransmitters that promote wakefulness, such as acetylcholine and serotonin.

One of the most relevant mechanisms during deep sleep is synaptic homeostasis. Following wakefulness, where neural connections strengthen and multiply in response to learning and experience, slow-wave sleep promotes a global and selective reduction in synaptic strength. This process, known as “synaptic downscaling”, restores balance and optimizes the efficiency of neural networks, allowing the brain to process information more accurately and efficiently the next day.

The metabolic cleansing function also takes on a leading role. The glymphatic system increases the elimination of neurotoxic substances, such as beta-amyloid and tau proteins. According to the magazine specialized in science and Hospitalthis mechanism is favored by an increase in brain interstitial space, which facilitates the purification of waste accumulated during wakefulness. The accumulation of these compounds has been linked to the appearance and progression of diseases such as Alzheimer’s.

It is also closely linked to the consolidation of declarative memoryrestoring attention and regulating brain aging mechanisms. Scientific evidence shows that a reduction in the quantity and quality of this phase impairs the ability to retain new information and is associated with structural changes that accelerate cognitive decline with age.

The risk of dementia

This stage of rest is one of the most important. A progressive reduction As age advances, it may translate into a higher risk of developing dementia.. According to a study published in JAMA Neurology, a chronic decrease in this deep phase of sleep is directly associated with an increased likelihood of suffering cognitive decline during subsequent years.

The follow-up of 346 participants, carried out over 17 years within the framework of the Framingham Heart Studyshowed that those who experienced an annual drop in the proportion of deep sleep had a 27% increase in the risk of developing dementia and 32% in the specific risk of Alzheimer’s.

The analysis highlights that this relationship does not depend on individual differences at a specific moment, but on the accumulated and sustained loss of slow wave sleep over time. The phenomenon is accentuated after the age of 60 and reaches its greatest speed between the ages of 75 and 80.which coincides with an accelerated deterioration of sleep architecture and a higher incidence of neurodegenerative diseases.

The research also identified associated factorssuch as the presence of cardiovascular diseasesthe use of medications that affect sleep and carrying the APOE ε4 allelea gene linked to increased risk of Alzheimer’s.

Furthermore, the information provided by Hospital highlights that chronic sleep problems can be one of the first signs of neurodegenerative pathologies, becoming a valuable element for early detection and prevention.

Meanwhile, the JAMA Neurology essay highlights that, although there is solid evidence of the association between the decrease in slow wave sleep and the appearance of dementia, it is still It has not been conclusively shown that loss of this phase causes the disease. It is also possible that brain processes linked to dementia contribute to a reduction in deep sleep, creating a negative feedback loop.