Reference; https://mbp-japan.com/jijico/articles/32380/
Modified and translated by CFJA
Is Poor Sleep and Indigestion a Hidden Cause Behind Cognitive Decline?
Table of Contents
What Is Dementia?
Dementia is defined as “a condition in which cognitive functions that had previously reached a normal level decline persistently due to acquired brain disorders, leading to interference with daily and social life.”
According to the International Classification of Diseases (ICD-10), it is described as “a syndrome caused by chronic or progressive brain disease, involving multiple impairments of higher cortical functions, including memory, thinking, orientation, comprehension, calculation, learning, language, and judgment.”
In Japan, data from a research team of the Ministry of Health, Labour and Welfare estimates that the number of elderly individuals with dementia will reach 4.716 million by 2025 and 5.842 million by 2040. This would mean that by 2040, approximately 15% of the elderly population, or 1 in every 6.7 people, would be living with dementia.
For the first time, estimates have also been released regarding Mild Cognitive Impairment (MCI)—a condition in which memory problems or similar symptoms are present but not severe enough to interfere with daily life or meet the criteria for a dementia diagnosis. The number of people with MCI is expected to reach 6.128 million by 2040.
Combined with the number of dementia cases, this results in 11.97 million people.
According to the Ministry of Internal Affairs and Communications, Japan’s total population in 2040 is projected to be approximately 108.33 million, meaning more than 10% of the population may face some form of cognitive decline.
The term “dementia” (ninchi-shō) has been officially used in Japan since December 24, 2004. Prior to that, the term “chiho-shō” (literally “idiocy”) was used, which conveyed the impression that it was simply severe forgetfulness associated with aging and something that happened naturally as people grew older.
In contrast, “dementia” is a broader term that recognizes the condition as stemming from widespread abnormalities in the brain. Today, dementia has become a significant social issue.
The impact of sleep deprivation is thought to be closely linked to long-term lifestyle habits established from a young age.
Do People with Dementia Struggle to Sleep Deeply?
You may have heard that as people age, they tend to wake up earlier and have more difficulty sleeping deeply. According to Japan’s Ministry of Health, Labour and Welfare’s “2023 Sleep Guidelines for Health Promotion,” the most common type of dementia is Alzheimer’s disease, which is characterized by a gradual progression of memory loss.
Alzheimer’s disease is believed to be associated with the accumulation of amyloid-beta and tau proteins in the brain. These proteins begin to build up decades before memory loss becomes apparent, and brain atrophy is thought to occur around 10 years after the initial accumulation begins. Increasing attention is being paid to the possibility that this protein buildup may be linked to sleep.
Several factors have been suggested as potential contributors to the development of Alzheimer’s disease, including:
- Insufficient or excessive sleep (less than 6 hours or more than 9 hours),
- Circadian rhythm sleep-wake disorders, and
- Obstructive sleep apnea.
It is believed that sleep plays a role in both the production and clearance of amyloid-beta in the brain—this may be one of the underlying mechanisms involved.
A study conducted in Italy found that approximately 60% of individuals with mild Alzheimer’s disease had some form of sleep disturbance. About 20% of participants reported difficulty falling asleep at night, waking up too early, or taking excessively long naps during the day.
Similar results have been reported in Japanese studies, showing that the prevalence of such sleep complaints increases with the severity of dementia. These issues are considered to result from disruptions in the sleep-wake cycle, leading to what is known as irregular sleep-wake rhythm disorder, where individuals are unable to maintain consolidated sleep during the night.
Such sleep disturbances are believed to increase the risk of behavioral symptoms associated with dementia, including agitation and wandering.