Daytime sleepiness, a sign of dementia?

▎Global Burden of Disease data compiled by WuXi AppTec content team shows that there were 57.
4 million dementia patients worldwide in 2019, and this number is expected to reach 150 million by 2050
.

Alzheimer's disease (AD) accounts for 60%-70% of dementia cases worldwide and is one of the major health challenges of the 21st century
.

The neurodegenerative conditions that lead to dementia, especially Alzheimer's disease, are often progressive, developing decades before the patient becomes disabled
.

Previous studies have confirmed that, long before Alzheimer's disease was clearly established, patients experienced 10 more frequent symptoms in the 15 years before diagnosis, including major depressive disorder, anxiety, severe stress and adjustment disorders, hearing loss, constipation, Spondylosis, abnormal weight loss, malaise and fatigue, memory loss, syncope and collapse
.

A new study published in Alzheimer's & Dementia recently confirmed that early progression of Alzheimer's disease accelerates changes in daytime sleep in the elderly population, and this relationship may be bidirectional
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The results of the analysis corroborate with the findings of another large-scale study published in Nature Communications, showing that people who regularly sleep less than six hours in midlife have a higher risk of developing Alzheimer's disease and dementia later in life
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Screenshot source: Alzheimer's & Dementia Sleeping more during the day is associated with a higher risk of dementia! Supplementary sleep during the day, such as napping, is a common life>
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A paper published today in Alzheimer's & Dementia reports the association between daytime sleep and Alzheimer's disease in older adults
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The researchers analyzed data from a Chicago-based study called the Rush Memory and Aging Project, which included 1,401 participants (median age at baseline, 81 years) who were followed for more than 14 years
.

Subjects recorded their daily activities by wearing a watch-like device
.

Daytime sleep is defined as a prolonged period of inactivity between 9 a.
m.
and 7
p.
m.

The results of the analysis showed that subjects who slept more than 1 hour a day had a 40% higher risk of developing Alzheimer's disease than those who slept less than 1 hour; 40% higher risk of Alzheimer's disease compared with subjects who slept at least 1 day The association between daytime sleep and Alzheimer's disease persisted despite factors such as gene carrier status; a bidirectional relationship was shown between daytime sleep and cognitive health: longer daytime sleep duration, higher frequency The subjects were associated with poorer cognitive function one year later; the subjects' poorer cognitive function was associated with more daytime sleep a year later
.

Overall, the duration and frequency of daytime sleep tended to increase with age, and the progression of Alzheimer's disease accelerated this change, resulting in an annual increase in the duration and frequency of daytime sleep.
more than double
.

Furthermore, daytime sleep and Alzheimer's disease may have pushed each other to produce changes
.

The researchers stress that this study is "the first to demonstrate a bidirectional relationship between daytime sleep duration (based on objective records) and Alzheimer's disease
.
"
Although there is currently insufficient evidence to establish a causal relationship between the two, whether daytime sleep has an impact on cognitive health, or whether excessive daytime sleep itself may accelerate aging or cognitive decline.
's signal
.

However, the association between excessive daytime sleepiness and dementia remained after adjusting for nighttime sleep duration and quality, suggesting that the role of daytime sleep itself is important and independent of nighttime sleep
.

Possible mechanism: Wake-promoting neuronal damage The findings of this study are consistent with findings recently published in JAMA Neurology
.

According to the latter study, it is hypothesized that daytime sleep is associated with the risk of dementia, and the underlying mechanism may be that individual nighttime sleep becomes fragmented due to the combined effect of amyloid-related damage and obstructive sleep apnea , and poor nighttime sleep quality causes the corresponding individual to always feel not fully awake during the day and choose to supplement sleep at a certain time during the day
.

▲ "Wake-up neurons" have already begun to degenerate in the early stage of Alzheimer's disease (Image source: 123RF) In addition, the study authors emphasized that because "wake-up neurons" have already begun to degenerate in the early stages of Alzheimer's disease , so this part of the population may not be tired during the day because they haven't slept well at night, but because the system in the brain that keeps them awake disappears
.

Based on objectively assessed sleep data and autopsy analyses, the research team confirmed their hypothesis that the reason Alzheimer's patients need daytime sleep is that the disease has damaged "wake-promoting neurons," and that damage occurs for a long time.
It is possible that it is due to the accumulation of tau rather than the accumulation of amyloid
.

The dangers of sleep deprivation in midlife A large observational study published last year in Nature Communications suggests that the relationship between sleep and the onset of dementia in later life may persist even in relatively young people
.

Screenshot source: Nature Communications After following nearly 8,000 British adults for up to 25 years, researchers have found that those who regularly sleep less than six hours in middle age have a higher risk of developing Alzheimer's disease in later life.
Zheimer's disease and dementia
.

Overall, people who slept less than 6 hours per night from middle age to old age (between 50 and 70 years old) had a 30% increased risk of developing Alzheimer's disease compared to people who maintained 7 hours of sleep per night for a long time
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The study also analyzed some possible influencing factors and found that the association between sleep duration in midlife and the risk of late-onset dementia was not related to psychiatric disease, cardiovascular metabolism or other known dementia-related chronic diseases
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In addition, there was no significant association between nighttime sleep duration ≥8 hours and dementia risk
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Although as a correlation study, the study cannot establish a causal link, the data tell us that sleep may be important for midlife brain health
.

Future research may further determine whether improving sleep habits can help prevent dementia, but even if we don't have clear results right now, it's always a good idea to get your sleep time right
.