Heat and Neurodegenerative Disorders

Excerpt from a piece on the science of heat therapy, written to be persuasive yet factual and evidence-based.

Imagine reaching your 85th birthday and still having your mind intact, your lifetime of memories, your ability to solve problems with ease, and your capacity to communicate effectively still sharp. Your life is a cohesive story that you can reflect on and find meaning in.   For about one-third of those who reach this milestone, this is not the case.  About 7.2 million people over age 65, or about 11% of the population, are living with Alzheimer’s Disease.  After age 65, the risk of developing the disease starts doubling every five years.  Alzheimer's Disease (AD) is the most common form of dementia and the sixth leading cause of death in the United States.

Sauna Studies

If you’ve been following along since the Kuopio Ischemic Heart Disease Risk Factor Study (KIHD), the decades-long Finnish project that showed sauna use slashes cardiovascular risk—you’ll know the Finns are onto something. But the most surprising results weren’t about the heart. They were about the brain.

The frequent sauna users, using their sauna four or more times a week, were 66% less likely to be diagnosed with dementia.  That’s not just “clinically significant,” that number is almost hard to swallow. So let’s look closer.

Why would heat protect the brain?

What is behind this potential risk reduction? I’ll give you a hint: it’s my favorite protein again. Heat shock proteins.  It turns out, the culprit behind neurodegenerative diseases is the build up of toxic protein aggregates. The very thing heat shock proteins are designed to combat. 

Neurodegenerative Diseases

Dementia isn't a single disease, but rather a term that describes a progressive decline in cognitive function that impacts daily life. Alzheimer's Disease accounts for 60-80% of all dementia cases. Parkinson's Disease (PD) is a neurodegenerative disease that primarily attacks the brain's movement centers.  And less common but faster progressing, Amyotrophic Lateral Sclerosis (ALS) aggressively destroys motor neurons, often proving fatal within just five years of diagnosis.

As with other degenerative disorders, these processes mirror the aging process.  Oxidative damage caused by reactive oxygen species, or ROS is a lifetime of “wear and tear” on our cells. For years the damage is minimal and cells function is unaffected. But over a lifetime damage slowly accumulates, and eventually hits a critical point where the cell’s defenses become overwhelmed. In the neurodegenerative diseases, we are not talking about vague or theoretical “cell damage.”  We know the exact proteins that cause the problems.  In Alzheimer’s, beta-amyloid and tau form plaques and tangles. In Parkinson’s, it’s alpha-synuclein fibrils. In ALS, mis-folded SOD1 piles up. The result? Neurons get clogged, cellular processes grind to a halt, and the brain malfunctions.

Protein Aggregates

Proteins are the essential workers if the cell, carrying out all the processes the cell needs to live and function. Each protein is folded into a precise three-dimensional shape that allows it to do its job. When a protein is damaged, the damage can disrupt the proper folding and shape.

Mis-folded proteins are often “sticky,” because hydrophobic amino acids (think oily) that are normally on the interior of the protein can become exposed. Multiple mis-folded proteins can clump together and form aggregates, which become even harder to repair or clear from the cell. The aggregates get in the way, “mucking up” the cell, to use a most official science term.

A cell is a crowded place.  Let’s go back to the crowded airport analogy.  Everyone has a mission.  There is a lot of stuff between you and your gate, or goal destination, that is irrelevant to you that you need to get past.  People, bags, carts, gates, chairs– as far as you are concerned, it all just gets in your way.  Misfolded proteins are the broken carts that stop short, block the walkways and cause a pileup. If no one clears them, the whole terminal shuts down. 

Heat shock proteins (HSP) are the cleanup crew—the molecular mechanics who refold broken proteins, dissolve dangerous clumps, or tow the hopeless cases to the proteasome to be disposed of.  They do this in every cell, every day.  Carts break down.  It’s not uncommon.  Normally the crew comes by and fixes it and gets it on its way before there is much of a slowdown in traffic at all.   

In the case of the neurodegenerative disorders, our heat shock proteins cannot keep up.  There are too many broken carts, and the damage is too severe, and the walkways are impassable before we can fix them all. Despite decades of research and the devastating impact these diseases have on families and society, treatments to meaningfully slow or stop the process have remained frustratingly elusive.  But the more we learn about heat shock proteins, the more interest there is in harnessing them and finding ways to increase what they are designed to do best- combat protein misfolding and toxic aggregates.  

Heat Shock Proteins

When our bodies experience elevated temperatures, they respond by increasing production of special protective proteins called heat shock proteins (HSPs), also known as molecular chaperones. These remarkable molecules act as the body's protein quality control system—they recognize damaged proteins, prevent harmful aggregation, and either guide proteins back to their correct shape or mark them for removal when they're beyond repair.

Scientists have become increasingly intrigued with these heat shock proteins as potential therapeutic targets for neurodegenerative diseases. The results of laboratory studies so far has only increased their hopeful excitement.

In Vitro Studies

In cell cultures designed to mimic Alzheimer's Disease, researchers can induce the accumulation of beta-amyloid—the primary component of the plaques that clog the brains of Alzheimer's patients. These beta-amyloid-laden neurons typically experience a six-fold increase in cell death. However, when the same neurons are also manipulated to overproduce heat shock protein 70 (HSP70), their death rates remain normal—as if the toxic proteins weren't even there3

Other chaperones show similar power. HSP27 reduces amyloid aggregates by 30–75% within 24 hours of being added to cultures. In Parkinson’s disease (PD) models, HSP70 inhibits formation of alpha-synuclein fibrils—the pathological species in PD—by up to ~80% over 24 hours.

Perhaps most striking, chaperone systems don’t just block new aggregates; they can disassemble pre-formed toxic fibrils into safer, non-aggregating species.

Animal Studies

Alzheimer’s models

The protective effects of heat shock proteins become even more compelling in animal studies. Transgenic mice engineered to express a plaque-prone APP variant develop AD-like pathology and cognitive deficits. Cross those mice with animals that overexpress HSP70, and the picture changes: less memory impairment (e.g., performance comparable to wild-type on tasks like the Morris Water Maze), fewer amyloid plaques, and reduced neuron loss in cortex and hippocampus. In another study, simply administering HSP70 through the nose reduced amyloid plaque formation by about 50% and protected against spatial memory deficits.

Pharmacologic HSP induction

A clinically used gastric cytoprotective in Japan, geranylgeranylacetone (GGA), is a known HSP inducer. In APP/PS1 mice fed GGA from 3 to 12 months of age, investigators found better performance on Y-maze, object recognition, and Morris Water Maze, along with lower Aβ levels, fewer plaques, and reduced synaptic loss. A dose-response study (200, 400, 800 mg/kg/day) similarly showed improved cognition and reduced amyloid-β peptide levels, implicating ERK/p38 MAPK signaling in HSP up-regulation.

Parkinson’s models

The same logic extends to PD. Overexpressing HSP70 in α-synuclein transgenic mice reduces abnormal α-syn aggregation and protects dopaminergic neurons, limiting α-syn-dependent toxicity. In a complementary rat model, introducing Hsp104 (a potent yeast disaggregase used experimentally) curbed α-syn aggregate formation and prevented neurodegeneration. After viral vector expression of mutant human α-syn (A30P), control rats lost ~33% of substantia nigra neurons at 6 weeks; with Hsp104 expression, loss fell to ~12.6%. Striatal terminal loss dropped from ~21.6% to ~7%.

ALS models

SOD-1 is an animal model of Amyotrophic Lateral Sclerosis (ALS).  In humans, 20% of familial cases of ALS carry mutations in the gene encoding Cu/Zn superoxide dismutase-1 (SOD1).  Exogenous HSP70, injected intraperitoneally three times weekly from day 50 to end stage, increased lifespan, delayed symptom onset, preserved motor function, and prolonged motor neuron survival. At day 120, 100% of HSP70-treated mice were alive, versus 67% with riluzole (the only FDA-approved ALS therapy) and 55% untreated Arimoclomol, a co-inducer that amplifies the heat shock response during cellular stress, delayed disease progression, improved hind-limb strength, preserved motor neurons in late disease, and extended lifespan by ~22% (16). Survival at day 120 rose from 33% in SOD1 controls to 65% when treatment started at day 75 and 57% when started at day 90.  

Application: Harnessing the Power of Heat    

These lab and animal findings provide a mechanistic backbone for the epidemiologic signal: regular heat exposure induces HSPs. Saunas deliver that stimulus safely and repeatedly, raising chaperone capacity so the brain can prevent toxic protein formation and, in early stages, dismantle what’s already accumulating.

While pharmaceutical HSP-modulators are still in development, heat is a non-invasive, accessible way to leverage the same biology—offering a plausible route to meaningful dementia-risk reduction as we age.