Slow-Wave Sleep May Lower the Risk of Alzheimer's Disease
According to a Xinhua report on September 10, 2024, an international study involving Lithuanian researchers shows that slow-wave sleep helps clear Alzheimer's-related proteins from the brain's metabolic waste and plays an important role in preventing Alzheimer's disease. The paper has recently been published in the American academic journal Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring.
As average life expectancy rises and the elderly population grows, Alzheimer's disease is becoming an extremely harmful condition. The Alzheimer's Association's 2020 Alzheimer's Disease Facts and Figures report shows that about one in three elderly people will eventually die from Alzheimer's or another dementia—more than breast and prostate cancer combined. Based on available data, the association estimated in 2019 that more than 50 million people worldwide had dementia, including Alzheimer's disease. By 2050 this figure could reach 152 million, and China alone would then have 50 million Alzheimer's patients.
The memory of Alzheimer's patients slips like quicksand; for them, the world and the loved ones around them grow strange. They no longer remember the important people and events in their lives, and they cannot even remember the way home. Family members must devote enormous effort to caring for them. To date there is no effective treatment for Alzheimer's disease, so prevention has become an urgent matter.
Normal human sleep is divided into rapid-wave (REM) sleep and slow-wave sleep. Slow-wave sleep is the stage in which the body rests most fully, also called deep sleep; its duration is considered the determinant of sleep quality. In children, slow-wave sleep promotes growth-hormone secretion and helps them grow; in adults, slow-wave sleep reduces the accumulation of beta-amyloid, and abnormal beta-amyloid deposition in the brain is one of the main pathological features of Alzheimer's. Abnormal beta-amyloid deposition may trigger a series of reactions—excessive tau protein phosphorylation and neurotransmitter disturbances—leading to neuronal damage.
The Lithuanian researchers found that, in the preclinical stage of Alzheimer's—when patients have not yet shown clinical symptoms but pathological markers have increased and their risk is higher—lower-quality slow-wave sleep is associated with abnormal tau accumulation and reduced cortical thickness, a marker of neuronal damage. These changes are especially evident in the temporal regions of the brain.
By taking sleep-intervention measures and using neuromodulation to enhance slow-wave sleep, this process can be reversed and the risk of Alzheimer's lowered. Laura Stankeviciute, a Lithuanian neurologist involved in the study, also noted that slow-wave sleep plays a unique role in memory consolidation, so high-quality nighttime rest is especially important for memory function; she advises healthy adults to sleep 7 to 9 hours each day.
Improving sleep quality is not especially difficult. By reducing stimulation to the brain before bed and putting yourself in a calm, relaxed state, most people can achieve better sleep quality. But some patients with intractable insomnia do need treatment. Nighttime slow-wave sleep is so important that we should value it; forming good sleep habits reduces trouble and expense for one's family, so why not?