Sauna has long term observational data. Cold water has real studies too, but not the same exposures, outcomes, or safety profile.
Sections
Walk into a gym with a two hundred dollar membership and you see the sales pitch, hot box on the left, ice tub on the right, sold together like the science came in a two pack. It didn’t. The sauna has a study that followed dudes for twenty years and counted who died, cold water has real studies too, but one of the better ones had people finish a shower with 30 to 90 seconds of cold water and counted sick days. Those aren’t even close to the same question.
You can like both, I don’t care, and neither one needs to become medicine before you’re allowed to enjoy it. The bullshit starts when a gym calls the pair a research backed contrast protocol and lets the sauna paper do the homework for the cold tub.
What the sauna study actually found
Researchers started with 2,315 men in Eastern Finland who were 42 to 60 years old. They recorded the men’s sauna habits at the beginning, then followed them for a median of 20.7 years. The guys going four to seven times a week had a 63 percent lower adjusted hazard of sudden cardiac death than the once a week group, with a hazard ratio of 0.37. The same general pattern showed up for fatal coronary disease, fatal cardiovascular disease, and death from any cause.1
That’s a hell of a signal. It’s also an observation, nobody assigned these guys to twenty years of sauna or no sauna, and the researchers only checked the habit at the beginning. Every participant was a middle aged Finnish man too, which matters if somebody is trying to sell the result as a guarantee for every body with a pulse.
The math accounted for a bunch of obvious differences, but math can’t scrub every lifestyle difference out of a group of humans. Guys who sauna constantly may do other healthy stuff, or they may be healthier to begin with and therefore more willing to sit in the heat. The study found a strong link. It didn’t prove the heat saved them.
It didn’t compare traditional heat with infrared cabins either, and nobody got assigned the perfect temperature, the perfect number of minutes, or the perfect cool down. It watched an existing Finnish habit. When a salesman gets very exact about doing 18 minutes at 174 degrees because this study supposedly proved it, he’s making up the last mile.1
Another analysis looked at 2,084 men and C reactive protein, one of the blood markers doctors use when they’re looking at inflammation. The men using a sauna more often had lower levels even after the researchers accounted for several health and lifestyle factors.2 Interesting, absolutely, but it still says the two things traveled together. It doesn’t say sauna treated a disease, and it doesn’t explain the death numbers from the first paper.
Cold water has data too
Cold plunges aren’t just vibes, but the evidence is narrower than the internet makes it sound. A randomized study put 3,018 adults into four groups. Three groups ended a normal hot shower with 30, 60, or 90 seconds of cold water for 30 days, and the fourth group kept showering normally. The cold shower groups reported 29 percent less sickness absence from work over the study, but they didn’t have fewer illness days.3
That counts. It also studied a quick cold shower, not sitting chest deep in a tub, and it measured calling out from work instead of heart attacks, depression, or how long anybody lived. Seventy nine percent finished the first 30 days and there were no related serious adverse events, which is reassuring for adults without severe health problems doing that exact routine. It isn’t a safety pass for a guy with heart disease sitting in colder water for longer.3
A cold shower and a plunge get filed under the same hashtag because that’s convenient for selling stuff, but your body isn’t reading the hashtag. Water temperature, how deep you go, how long you stay, whether you’ve adapted to cold, and whether you’ve got a heart problem all change what you’re actually doing. Until a study spells those out, a very precise commercial protocol can be a lot more precise than the evidence.
If the jolt makes you feel good, that’s enough reason to keep it. Feeling awake after cold water doesn’t magically turn into proof that you’ll have fewer heart attacks, and nobody gets to fill that gap in with enthusiasm and a discount code.
Cold can wake up brown fat
Brown fat is real heat-making tissue in adults. Mild cold can make it burn fuel to produce heat without shivering, and a 10-day controlled cold-acclimation study found higher brown-fat activity and more non-shivering heat production. That tells us cold exposure does something measurable. It doesn’t prove a plunge melts body fat, prevents disease, or earns the same claims as the sauna studies.7
The hot and cold combo is where it gets slippery
The sauna paper studied sauna, the shower paper studied showers, and neither one studied the fancy back and forth routine getting pushed all over social media. This seems painfully obvious when it’s written out, yet the marketing puts both citations under one heading and hopes nobody notices which box did what.
The American Heart Association says people with controlled high blood pressure should generally tolerate a sauna, although anybody worried about it should talk with a health professional. It also tells people with high blood pressure not to bounce between cold water and a hot tub or sauna because that can raise blood pressure. Alcohol and sauna don’t mix either.4
That’s not the sexy part of contrast therapy, but it’s the part you need if you’ve got an arrhythmia, heart disease, blood pressure trouble, diabetes, or medication that changes how your body handles heat. The fact that the gym put a eucalyptus towel next to the tub doesn’t make the cold shock less real.
Don’t make this a toughness contest
New Jersey put out specific guidance for public cold plunge tubs in 2025, and the warning is pretty blunt. Sudden temperature changes can screw with breathing and coordination, cause muscle cramps, and knock somebody unconscious. The guidance says people should talk with a doctor before using a cold plunge, shouldn’t use one alone, and shouldn’t mix it with alcohol or drugs.5
Open water is a whole other level of stupid if you treat it like the tub at a spa. The National Weather Service warns that cold shock can cause an involuntary gasp, rapid breathing, sudden changes in heart rate and blood pressure, muddled thinking, loss of muscle control, and drowning. They tell people to check the water and weather, wear flotation, and get out as soon as it’s safe after an unplanned dunk.6
- Heart disease, diabetes, high or low blood pressure, pregnancy, or prescription medication means you talk with somebody who knows your medical history first.
- No booze, no solo plunge, and no pretending dizziness is a character building exercise.
- Drink water like you actually like it, you’re gonna need it. The hydration basics are boring right up until you ignore them in a room built to make you sweat.
- If you’re dizzy, confused, about to faint, or can’t get your breathing under control, get out. Nobody gets a medal for passing out in a stock tank.
What you’re actually paying for
If your reason is that either one feels good, go do it and have a nice Saturday. If you’re paying because somebody promised heart protection, make him show you the study. The sauna pitch at least has the Finnish cohort behind it, with the limits we just went through. The plunge pitch has a cold shower study about sick leave, which is real data and a completely different purchase.
The same goes for using heat or cold because your nervous system has been grinding all week. A ritual can take the edge off without fixing the bigger reason you’re fried. If sleep and stress are a mess, deal with those too instead of asking an ice tub to become your therapist.
Put the sauna and the plunge next to each other in the gym, dude, that’s fine. It still doesn’t merge the studies, and it sure as hell doesn’t let one borrow the other’s claims.
Sources
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine. 2015;175(4):542-548. (PMID 25705824). DOI: 10.1001/jamainternmed.2014.8187.
- Laukkanen JA, Laukkanen T. Sauna bathing and systemic inflammation. European Journal of Epidemiology. 2018;33(3):351-353. (PMID 29209938). DOI: 10.1007/s10654-017-0335-y.
- Buijze GA, Sierevelt IN, van der Heijden BC, Dijkgraaf MG, Frings-Dresen MHW. The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLOS One. 2016;11(9):e0161749. (PMID 27631616). DOI: 10.1371/journal.pone.0161749.
- American Heart Association. Getting Active to Control High Blood Pressure. Last reviewed August 14, 2025.
- New Jersey Department of Health. Cold Plunge Unit Guidance Document. December 22, 2025.
- National Weather Service. Cold Water Hazards and Safety. Accessed August 6, 2026.
- van der Lans AAJJ, Hoeks J, Brans B, et al. Cold acclimation recruits human brown fat and increases nonshivering thermogenesis. Journal of Clinical Investigation. 2013;123(8):3395-3403. (PMID 23867626). DOI: 10.1172/JCI68993.