The Wild Sauna Data My Mom Couldn't Stop Talking About

Today, we're highlighting some wild data that's been out there for years but that so many people still haven't acted on.

This includes my own mom, who called me last week super excited because she listened to our episode with Bill Gifford on the power of sauna and, in particular, got really excited about the Alzheimer's data.

She'd been using the sauna here and there over the years, but seeing this data has her motivated to make it a regular practice.

Now, I've talked about it before, but I carry a copy of the APOE4 gene, which means that at least one of my parents likely carries this risk factor as well. We also have some family history of dementia on my mom’s side.

So dementia and Alzheimer's disease risk reduction is not only on my mind, it's 100 percent on my mom's mind as well.

The truth is, we still do not have a drug proven to reliably prevent Alzheimer's disease in otherwise healthy people. But we do have data on something powerful that keeps showing effect sizes our pharmaceuticals cannot touch.

It's the power of sauna.

In today's newsletter, we're going to get into the data on it.

The 65 Percent Number

A long-running, population-based Finnish cohort study of middle-aged Finnish men found that more frequent sauna bathing was strongly associated with a lower risk of dementia and Alzheimer's disease, even after accounting for known risk factors. 

This study found that men who used a traditional sauna 4 to 7 times per week had a 65 percent lower risk of Alzheimer's disease compared with men who used the sauna once per week.

The researchers believe this is biologically plausible because sauna use improves vascular function, reduces inflammation, and lowers blood pressure—all of which are linked to dementia risk.

In 2020, a separate Finnish research team studied nearly 14,000 men and women. Over the first 20 years of follow-up, people who used the sauna 9 to 12 times per month had about half the dementia risk compared with those who used it rarely or not at all.

The association was seen in both men and women.

What These Studies Did and Didn't Show

These were not randomized trials. Healthy-user bias is real. People who sauna regularly may also do other things that protect their brain.

The 2020 data also suggested that very high sauna temperatures, above 212°F, were associated with higher dementia risk, not lower risk.

And the heaviest users did not appear to get extra benefit.

So the takeaway is not “more heat is always better.”

The takeaway is consistency, in a reasonable range.

Why It Probably Works

Researchers have a few theories on why sauna seems to be so protective.

One is that heat stress activates heat shock proteins, which Bill calls "mommy proteins." These proteins help cells manage damaged and misfolded proteins, breaking up clumps and keeping cellular machinery functioning. That matters here because the amyloid plaques and tau tangles you've heard about in Alzheimer's are exactly that: aggregates of misfolded proteins, the kind of cellular debris that heat shock proteins help clean up.

The second theory is vascular. Dementia is increasingly understood as a disease of the brain's blood vessels as much as the brain's neurons. Stiff, inflamed arteries reduce blood flow and oxygen delivery to the brain. Sauna can raise your heart rate into the 120 to 150 range, similar to a moderate workout. Frequent sauna users have lower blood pressure, more flexible arteries, and better endothelial function. These are the same cardiovascular improvements you'd get from exercise.

Heart health and brain health are deeply linked. Sauna seems to act on both at the same time.

What I'm Telling My Mom and Dad

Two to three sessions per week, 15 to 20 minutes each, around 160 to 195°F.

No flight to Finland required. Even regular hot baths show meaningful and similar benefits, which you can read about here. 

Start lower and shorter if you're new. Hydrate. Avoid alcohol. And check with your doctor if you're pregnant, prone to fainting, on blood-pressure medication, or dealing with heart disease.

The point is consistency.

I cannot promise this will prevent Alzheimer's. The disease is too complex.

What I can tell you is this: as far as low-cost, accessible habits go, sauna belongs in the conversation.

Thank you to Bill Gifford for the work he poured into Hotwired. Listen to our full conversation on The Dhru Purohit Show.

Here's to your health.
Dhru Purohit

The information in this newsletter is for educational purposes only and should not be construed as medical advice; please consult a qualified healthcare professional before making any health-related decisions.