A wave of recent scientific findings underscores that not all sleep is created equal—deep sleep and rapid eye movement (REM) sleep are emerging as key guardians of brain health, with profound implications for dementia risk and cognitive aging. The latest research, recently highlighted in a New York Times report, confirms that beyond simply getting enough hours of sleep, the specific quality and stages of sleep matter deeply for long-term mental wellbeing (NY Times, 2025).
For Thais contending with rising rates of sleep problems, from urban insomnia to undiagnosed sleep apnea, understanding how different sleep stages impact the brain holds significant meaning. The connection between insufficient restorative sleep and a greater likelihood of Alzheimer’s disease and other forms of dementia brings urgency to an issue sometimes overshadowed by daily stress and social nightlife culture.
Years of disrupted or poor-quality sleep—especially skimping on the most restorative phases—dramatically increases the risk of dementia and cognitive decline, recent studies show. A major longitudinal study following adults in their 30s and 40s found those with highly disrupted sleep (marked by frequent awakenings and movements) had a two- to three-fold greater risk of showing significant declines in executive function, working memory, and information processing speeds a decade later. This isn’t just a matter of feeling sleepy at work—such declines translate into real-world problems with attention, decision-making, and even job performance.
What makes deep and REM sleep so unique? Scientists have mapped four distinct sleep phases: two lighter stages, followed by deep (slow-wave) sleep, and finally REM sleep, where most dreaming occurs. Deep sleep sees the brain’s activity slow dramatically—the body uses this time to repair tissues, balance hormones, and, crucially, perform a kind of nightly “rinsing” that flushes out waste products like amyloid proteins, which are linked to Alzheimer’s. As noted by a leading professor of neurology at a top U.S. medical center, this so-called “glymphatic system” is essential to keeping the brain clear of the plaques that can lead to neurodegenerative diseases.
Meanwhile, REM sleep is where memories, emotional experiences, and new information from the day are processed and stored. Cutting-edge MRI studies published this year have shown that brains of people with chronic deficiencies in deep or REM sleep displayed patterns of thinning and atrophy in areas vital for memory and cognition, alarmingly similar to the early stages of Alzheimer’s. An associate professor at a Melbourne-based psychological sciences faculty confirmed that these brain changes were detected up to 17 years after the original sleep deficiencies were recorded—a sobering timeline that suggests early adulthood sleep quality may set the stage for later brain health.
The relationship between sleep and dementia risk is not totally straightforward, researchers caution. As adults age, particularly women, the amount of time spent in deep and REM sleep naturally decreases, while the risk of sleep disruptions increases. Dementia itself also tends to further degrade sleep quality, creating a vicious cycle. Expert commentary from a North American sleep medicine professor stresses that current evidence does not yet prove poor sleep “causes” dementia outright, but robust associations are now clear enough to warrant urgent attention.
For Thailand, where data from the Ministry of Public Health show over a third of adults report symptoms of insomnia or non-restorative sleep, these findings demand national awareness and targeted prevention strategies. The country’s rapidly aging population portends a sharp increase in dementia cases in the coming decades, with direct costs to families, the healthcare system, and the wider economy. Sleep health must be considered a modifiable risk—alongside better-known factors such as hypertension and diabetes—in any comprehensive strategy to address cognitive aging.
So, what can be done? While directly boosting deep or REM sleep remains challenging, simple sleep hygiene practices make a difference. According to a leading psychiatrist at a California university, people who regularly get six hours or less of sleep in midlife have a 30% greater risk of developing dementia in later years. Experts recommend aiming for at least seven hours per night to allow the brain to cycle through all necessary stages four to seven times. Maintaining a regular sleep and wake schedule improves one’s chances of drifting into deeper stages.
Other practical interventions recommended by Cambridge brain researchers include mentally engaging activities, such as learning new skills—a practice embedded in Thai culture through activities at community “houses of wisdom” (ศูนย์เรียนรู้ชุมชน)—which heighten the brain’s demand for restorative sleep and help consolidate memories. Regular exercise, another core part of Thai daily life, increases blood circulation to the brain and supports the glymphatic clearance process; even the traditional Thai morning run in Lumpini Park or light group aerobics can offer benefits. Stress reduction techniques, like mindfulness and meditation widely taught in Thai schools and monasteries, further enhance sleep quality according to sleep scientists.
Recognising signs of inadequate sleep is also critical. Although wearable sleep trackers and smartphone apps are gaining popularity in Thailand’s tech-savvy urban centres, experts caution that subjective measures are often more telling. As one sleep medicine professor put it, ask “Do I wake up feeling refreshed?” and monitor how easily one returns to sleep after nighttime awakenings.
Culturally, Thais may face unique challenges. Evening work, late-night street food culture, and digital distractions often delay bedtimes, especially in bustling Bangkok and Chiang Mai. However, rural traditions that favour early rising and winding down with family before bed—or the practice of evening meditation in temples—may provide models for protective sleep routines.
Looking ahead, the implications for public health policy are profound. Sleep quality should be promoted in Thai national health campaigns alongside smoking cessation and healthy diet, especially for older adults and at-risk populations. Medical practitioners should screen for sleep problems alongside cognitive checks in elderly patients. Further research led by Thai institutions could explore how local customs, diet, and lifestyle affect sleep architecture and dementia outcomes in the Thai population, providing insights for ASEAN neighbours facing similar demographic transitions.
For individual Thais, the recommendations are clear: Prioritise sleep as a foundation of health. Go to bed and wake up at similar times daily, aim for seven hours, engage your mind with meaningful activities, exercise regularly, and tend to your mental wellbeing. For society, bridging traditional wisdom with modern sleep science may offer a culturally resonant path toward keeping Thai minds sharp for years to come.
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