Quality sleep is one of the foundations of health, and a new study suggests that poor sleep quality is a major risk factor for developing Alzheimer’s disease and other dementias.
Dementia is a rising global problem
Worldwide, close to fifty million people currently live with Alzheimer’s disease or other forms of dementia. According to the World Health Organization, that number is expected to potentially triple by 2050.
Dementia is a chronic age-related condition that affects the brain and leads to a deterioration of cognitive function. People who suffer from this condition typically struggle with memory, thinking, orientation, learning, understanding language, calculation, and judgement. This is often accompanied by a decline of emotional control and social behavior.
Poor sleep is a major risk factor for dementia
The results of a recent study suggest that getting enough high-quality sleep could reduce the risk of developing dementia by a considerable amount along with all-cause mortality .
It is well known that getting sufficient sleep is important for health and that not enough or broken sleep puts you at risk for various chronic conditions, such as heart disease, diabetes, stroke, obesity, and kidney disease.
The researchers of this study wanted to examine the link between poor sleep quality, or sleep deficiency, and developing dementia. To do this, the researchers used data from the National Health and Aging Trends Study (NHATS), an ongoing study of older adults in the US. Over 2800 people with an average age of 77 participated in the study. They completed questionnaires about their sleep quality.
The researchers then followed the participants for five years to see how many developed dementia or passed away from other causes. They discovered that people who reported having less than 5 hours of sleep a night had double the risk of developing dementia than people who slept 7-8 hours a night. Also, people who took longer than 30 minutes to fall asleep once in bed had a 45% increased risk of developing dementia.
Additionally, people who had less than 5 hours sleep a night, daytime sleepiness, and a need for regular daytime naps experienced increased mortality during their 5-year participant follow-up.
Your brain needs sleep to wash itself clean
This study’s findings are unsurprising given that the brain cleans itself during sleep via the glymphatic system, which mostly happens during deep (slow wave) sleep. This system consists of a series of vessels that surround the brain and uses cerebrospinal fluid (CSF) to distribute essential molecules and remove waste build-up from the brain .
This includes removing amyloids such as amyloid beta, which is associated with Alzheimer’s disease. Amyloid beta accumulates during aging, forming plaques in the brain, can interfere with the synapses between neurons, and is likely the major factor in the development of Alzheimer’s and other types of dementia.
It is also likely the case that amyloid plaques also interfere with sleep quality and make deep sleep difficult. Research suggests that this becomes a vicious cycle where poor sleep increases the buildup of plaques, which then further harms sleep quality and leads to more plaques. This feedback loop then leads to increasingly poor brain health and the probable onset of dementia.
Background: Sleep disturbance and deficiency are common among older adults and have been linked with dementia and all-cause mortality. Using nationally representative data, we examine the relationship between sleep disturbance and deficiency and their risk for incident dementia and all-cause mortality among older adults.
Methods: The National Health and Aging Trends Study (NHATS) is a nationally-representative longitudinal study of Medicare beneficiaries in the US age 65 and older. Surveys that assessed sleep disturbance and duration were administered at baseline. We examined the relationship between sleep disturbance and deficiency and incident dementia and all-cause mortality over the following 5 years using Cox proportional hazards modeling, controlling for confounders.
Results: Among the sample (n = 2,812), very short sleep duration (=5 hours: HR = 2.04, 95% CI: 1.26 – 3.33) and sleep latency (>30 minutes: HR = 1.45, 95% CI: 1.03 – 2.03) were associated with incident dementia in adjusted Cox models. Difficulty maintaining alertness (“Some Days”: HR = 1.49, 95% CI: 1.13 – 1.94 and “Most/Every Day”: HR = 1.65, 95% CI: 1.17 – 2.32), napping (“Some days”: HR = 1.38, 95% CI: 1.03 – 1.85; “Most/Every Day”: HR = 1.73, 95% CI: 1.29 – 2.32), sleep quality (“Poor/Very Poor”: HR = 1.75, 95% CI: 1.17 – 2.61), and very short sleep duration (=5 hours: HR = 2.38, 95% CI: 1.44 – 3.92) were associated with all-cause mortality in adjusted Cox models.
Conclusions: Addressing sleep disturbance and deficiency may have a positive impact on risk for incident dementia and all-cause mortality among older adults.
What you can do to help improve sleep
So, given that poor-quality sleep is a major risk factor for developing Alzheimer’s and other dementias, what can you personally do?
Some sleep strategies that may help:
- Keep the room temperature cool when sleeping, around 60 to 67 degrees Fahrenheit (15.6 to 19.4 degrees Celsius) is ideal. Everyone is different, so experiment.
- Avoid bright light in the evening.
- Make use of blackout curtains to reduce ambient light in the room.
- Avoid light sources from devices such as LED bedside clocks.
- Seek bright light in the morning.
- Avoid caffeine, alcohol, and other stimulants in the evening.
- Avoid using sleeping tablets as some data suggests they can reduce brain plasticity in animal studies and may increase cancer risk.
- You may wish to invest in a health wearable watch, and even some lower-end models now include sleep monitoring. This will allow you to ascertain if the above measures are helping you get enough quality sleep.
Note that this is not intended as medical advice, but you may find that some of these ideas help to improve sleep quality.
Sleep, exercise, social interaction, and a balanced, healthy diet are the cornerstones of health and could allow you to remain in good health for longer. We are living during a historical time in which researchers are starting to unravel the secrets behind the aging processes. In the future, that science could help us all to live longer, independent and healthy lives, but before we reach that point, we should strive to maintain our health to live long enough to benefit from that science.
We could be a decade or perhaps more from the arrival of the first rejuvenation technologies capable of addressing one or more of the aging processes directly. This is why it is important to do everything you can to increase your chances of being here when those technologies finally arrive. Ensuring that you get enough quality sleep is an essential part of an effective longevity strategy and something that we can all work on personally.
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 Robbins, R., Quan, S. F., Weaver, M. D., Bormes, G., Barger, L. K., & Czeisler, C. A. (2021). Examining sleep deficiency and disturbance and their risk for incident dementia and all-cause mortality in older adults across 5 years in the United States. Aging (Albany NY), 13(3), 3254.
 Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., O’Donnell, J., Christensen, D. J., Nicholson, C., Iliff, J. J., Takano, T., Deane, R., & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science (New York, N.Y.), 342(6156), 373–377. https://doi.org/10.1126/science.1241224
June 2, 2021
https://pubmed.ncbi.nlm.nih.gov/33573456/ (doi: 10.1089/rej.2020.2388. Online ahead of print).
In an article Victor Björk (present at HEALES meetings) about the Suprachiasmatic nucleus. He’s calling for more research.
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