Alzheimer’s disease, the world’s most common neurodegenerative disease and form of dementia, is partly a disease of protein misfolding. Basically, two proteins called beta-amyloid and tau misfold and aggregate, forming the amyloid plaques and neurofibrillary tangles that are the hallmarks of Alzheimer’s. (Other neurodegenerative and chronic diseases are also diseases of protein misfolding, such as Parkinson’s disease, which involves the misfolding of alpha-synuclein.)
Thus, the prevention of misfolding, could potentially positively impact your risk of Alzheimer’s disease, Parkinson’s disease, and maybe more diseases.
So, what causes protein misfolding? Well, for one, age. The older you are, the more misfolded proteins accumulate. But heat also causes proteins to unfold and misfold. Perhaps you recall from high school biology something called “denaturation.” When proteins are heated, they lose their three-dimensional structure and can misfold.
Where am I going with all this? Well, your body is smart and adaptive. When you expose it to heat, it responds by making proteins called Heat Shock Proteins (HSPs) to protect the proteins in your cells from misfolding. It’s similar to when you work out and your muscles grow in response (both heat stress and working out are examples of “hormetic stressors,” environmental stressor that tax the body and force it to adapt to become more resilient).
But do your muscles go away when you stop working out? Nope. And neither do the HSPs, at least not over the short term. They stick around and continue to protect your proteins from misfolding. What this means, at least in theory, is that heat stress could protect you against developing Alzheimer’s disease.
But theory only is not enough. Show us the data!!! If you say so…
Not only do studies in animals support the model that heat stress increases HSP levels and, thereby, protects against age-related diseases like Alzheimer’s, but other studies demonstrate that gain-of-function mutations in HSP genes in humans are associated with longer lifespans. (See this Publication and Article)
More to the point, a really cool 2017 study, published in Age and Aging, suggests that sauna use (heat stress) is an independent predictor of decreased Alzheimer’s risk! For this study, the researchers followed over 2,000 Finnish sauna users for over 20 years, over which time incidences Alzheimer’s disease were recorded.
The researchers found a dose-dependent effect of sauna use on Alzheimer’s disease risk: more sauna use was associated with a lower likelihood of developing Alzheimer’s. Specifically, people who used the sauna 4-7 times per week were 65% less likely to develop Alzheimer’s than those who used the sauna only once per week (hazard ratio = 0.35, p = <0.01).
In five words: Hot Heads Protect Against Alzheimer’s.
Critically, this association held true even after the researchers adjusted for age, BMI, blood pressure, LDL levels, smoking, alcohol use, type 2 diabetes status, cardiorespiratory fitness, resting heart rate, physical activity, and socioeconomic status, suggesting the correlation wasn’t influenced by confounding healthy user bias.
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