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Randomized trials of regular heat found few lasting changes in heart risk markers

This 2025 analysis in the American Journal of Preventive Cardiology pooled the results of 20 randomized trials that gave people passive heat for at least a week.

The paper

Non-acute effects of passive heating interventions on cardiometabolic risk and vascular health: systematic review and meta-analysis of randomized controlled trials

Hamaya R, Joyama Y, Miyata T, Fuse SI, et al.. American Journal of Preventive Cardiology, 2025;23:101082.

Read the paper ↗PubMed 41049507 ↗Free full text ↗

See the study at a glance

Design
Systematic review and meta-analysis of randomized trials
People
20 randomized trials
Who they were
The review drew on 20 randomized trials of passive heating. Some enrolled people with coronary risk factors or cardiovascular disease.
What they did
The included trials used hot-water immersion, sauna, hot yoga or local heating and lasted at least a week. The search ran to November 2024, and the review was registered in advance.
How long
2–15 weeks per trial

These numbers came out of it

−2.46

Across all the trials, systolic blood pressure changed by this much (mmHg). The plausible range ran from −5.02 to 0.10, so the result wasn't significant.

−4.11

Systolic pressure fell this much in the trials that heated the whole body.

−2.52

In people with coronary risk factors or heart disease, systolic pressure fell this much.

None

No significant pooled change showed up in blood vessel function (flow-mediated dilation), artery stiffness (pulse wave velocity), blood sugar, cholesterol or the inflammation marker CRP.

The researchers did this

Hamaya and colleagues gathered randomized trials that gave people passive heat for at least a week and measured heart and metabolic risk. They found 20 that used hot water, saunas, hot yoga and local heating, and the programs lasted from two to 15 weeks.Source 1 · Meta-analysisNon-acute effects of passive heating interventions on cardiometabolic risk and vascular health: systematic review and meta-analysis of randomized controlled trialsHamaya R, Joyama Y, Miyata T, et al.. American Journal of Preventive Cardiology, 2025.Read the paper ↗PubMed ↗

Across the trials, systolic blood pressure fell by 2.46 mmHg on average, and its plausible range of −5.02 to 0.10 includes no change. The trials' results varied a lot (I² 60.3%).Source 1 · Meta-analysisNon-acute effects of passive heating interventions on cardiometabolic risk and vascular health: systematic review and meta-analysis of randomized controlled trialsHamaya R, Joyama Y, Miyata T, et al.. American Journal of Preventive Cardiology, 2025.Read the paper ↗PubMed ↗

Two subgroups showed significant falls in systolic pressure. It dropped 4.11 mmHg in trials that heated the whole body and 2.52 mmHg in people with coronary risk factors or cardiovascular disease. Flow-mediated dilation, pulse wave velocity, heart rate variability, blood sugar, cholesterol and CRP showed no significant pooled effect.Source 1 · Meta-analysisNon-acute effects of passive heating interventions on cardiometabolic risk and vascular health: systematic review and meta-analysis of randomized controlled trialsHamaya R, Joyama Y, Miyata T, et al.. American Journal of Preventive Cardiology, 2025.Read the paper ↗PubMed ↗

Because it admitted only randomized trials, this is the strictest of the pooled analyses, and its results are the least favorable. A 2025 analysis of 51 controlled studies found a 5 mmHg fall in systolic pressure after repeated heating, and a 2021 analysis found about 4 mmHg.Source 2 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗Source 3 · Meta-analysisThe effect of heat therapy on blood pressure and peripheral vascular function: A systematic review and meta‐analysisPizzey FK, Smith EC, Ruediger SL, et al.. Experimental Physiology, 2021.Read the paper ↗PubMed ↗

The study can't tell you these things

  • The abstract doesn't give the pooled number of participants or trial-by-trial details.
  • The trials mixed very different kinds of heat, from local heating to hot yoga, so a pooled figure blends them.
  • The programs lasted two to 15 weeks, and the trials measured risk markers without tracking heart attacks or deaths.
  • One printing of the abstract drops the minus sign on the lower limit and shows the systolic interval as 5.02 to 0.10.

People quote it like this

The whole-body heating subgroup is the part most likely to be quoted in favor of saunas, although the estimate across all 20 trials wasn't significant.

We cited these sources

  1. 01Hamaya R, Joyama Y, Miyata T, Fuse SI, Yamane N, Maruyama N, et al.. Non-acute effects of passive heating interventions on cardiometabolic risk and vascular health: systematic review and meta-analysis of randomized controlled trials. American Journal of Preventive Cardiology. 2025;23:101082. doi:10.1016/j.ajpc.2025.101082 PMID 41049507
  2. 02Price BS, Lucas SJE, Akerman AP, Gilworth RE, Lucas RAI. Heat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysis. Experimental Physiology. 2025:EP092404. doi:10.1113/EP092404 PMID 41166412
  3. 03Pizzey FK, Smith EC, Ruediger SL, Keating SE, Askew CD, Coombes JS, et al.. The effect of heat therapy on blood pressure and peripheral vascular function: A systematic review and meta‐analysis. Experimental Physiology. 2021;106(6):1317-1334. doi:10.1113/EP089424 PMID 33866630