Evidence Trace, complete trial record
In plain terms
In plain terms: Traditional Finnish Sauna (dry sauna) shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
Traditional Finnish Sauna (dry sauna)
C
Limited: small, mixed or unreplicated trials
The endpoint this grade is based on: Surrogate biomarker endpoint
The evidence as the record states it
Lee et al. (Am J Physiol Regul Integr Comp Physiol, 2022; PMID 35785965): 47 adults, sauna after exercise for 8 weeks lowered systolic pressure and raised fitness more than exercise alone. Debray et al. (J Appl Physiol, 2023; PMID 37650138): 41 adults with coronary disease, 8 weeks of sauna, no change in vascular function or blood pressure. Lee et al. (Physiol Rep, 2025; PMID 40611569): sauna after exercise added nothing to heart rate variability. Kanji et al. (J Altern Complement Med, 2015; PMID 25636135): 37 adults, less tension-type headache pain. Pach et al. (Med J Aust, 2010; PMID 21143077): 157 adults, breathing hot sauna air did not ease a cold. Gayda et al. (J Clin Hypertens, 2012; PMID 22863164): in single sessions, exercise followed by sauna lowered 24-hour blood pressure in untreated hypertension. Grade C: small, short trials on blood pressure, fitness and self-reported pain, with null results beside them.
PMID 35785965 PMID 37650138 PMID 40611569 PMID 25636135 PMID 21143077 PMID 22863164
Evidence by specific use
Blood pressure and fitness when sauna follows regular exercise
Grade C
Lee et al. (Am J Physiol Regul Integr Comp Physiol, 2022; PMID 35785965): 47 sedentary adults with a cardiovascular risk factor, randomized to exercise plus 15 minutes of sauna, exercise alone or no change for 8 weeks; adding sauna lowered systolic pressure by 8 mmHg more than exercise alone (95% CI -14.6 to -1.4) and raised VO2max by 2.7 mL/kg/min more. Gayda et al. (J Clin Hypertens, 2012; PMID 22863164): 16 adults with untreated hypertension, single sessions in crossover; exercise followed by sauna lowered 24-hour systolic pressure. Against them, Debray et al. (J Appl Physiol, 2023; PMID 37650138): 41 adults with coronary disease, 8 weeks of sauna alone, four sessions a week; blood pressure did not change. One small positive trial of sauna added to exercise, not repeated by an independent group, and one trial of sauna alone that found nothing: C.
PMID 35785965 PMID 22863164 PMID 37650138
Vascular function in stable coronary artery disease
Grade D
Debray et al. (J Appl Physiol, 2023; PMID 37650138): 41 adults with stable coronary disease randomized to 8 weeks of Finnish sauna (79 degrees Celsius, 20 to 30 minutes, four times a week) or no change. Resting core temperature fell and sweating rose, so the body adapted to the heat, but flow-mediated dilation, arterial stiffness and blood pressure did not differ from control. A single session in a similar population raised flow-mediated dilation for about an hour (Gravel et al., 2021, listed below under why the claim persists), which is why the acute finding and the 8-week finding are shown apart. Tested, no benefit.
PMID 37650138
Heart rate variability when sauna follows regular exercise
Grade D
Lee et al. (Physiol Rep, 2025; PMID 40611569): 38 sedentary adults randomized to exercise plus 15 minutes of sauna, exercise alone or control for 8 weeks. Exercise improved heart rate variability; adding sauna gave no further change on any measure. Tested, no benefit.
PMID 40611569
Chronic tension-type headache pain
Grade C
Kanji et al. (J Altern Complement Med, 2015; PMID 25636135): 37 adults with chronic tension-type headache randomized to advice plus regular sauna or advice alone for 8 weeks. Headache intensity fell by 1.27 points more on a 10-point scale with sauna (95% CI 0.48 to 2.07). Headache duration, sleep, depression scores and headache disability did not differ. One small unblinded trial on a self-reported endpoint: C.
PMID 25636135
Common cold symptoms, breathing hot sauna air during a cold
Grade D
Pach et al. (Med J Aust, 2010; PMID 21143077): 157 adults with a new cold sat in a hot sauna in winter coats and breathed either hot dry air or room-temperature air for 3 days. Overall symptom severity did not differ (difference -3.9, 95% CI -9.7 to 1.9). Day 2 symptoms, day 1 medication use and self-rated effectiveness favored hot air. The primary endpoint was null. Tested, no benefit.
PMID 21143077
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What this grade covers and what it does not
Grade C. The randomized evidence on the traditional Finnish sauna is small and short. Sauna added after exercise lowered systolic pressure and raised fitness in one 47-person, 8-week trial (Lee et al., 2022; PMID 35785965), which has not been repeated by an independent group, and sauna alone changed neither vascular function nor blood pressure in 41 people with coronary disease over the same 8 weeks (Debray et al., 2023; PMID 37650138). Blood pressure is an established stand-in for heart disease, but one positive trial against one null trial does not meet the B definition. Headache pain fell in one 37-person unblinded trial (Kanji et al., 2015; PMID 25636135), a self-reported endpoint from a single trial. WHAT THIS GRADE DOES NOT COVER: mortality, dementia and stroke. The Kuopio cohort findings (PMID 25705824; PMID 27932366; PMID 29720543) are observational, and no randomized trial has tested sauna against any of those outcomes. Infrared saunas and the Japanese Waon protocol are a different exposure and are graded on their own record.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.
How this was studied
Form: A traditional sauna heated by a stove, about 79 to 81 degrees Celsius at 13 to 23 percent relative humidity in the trials that reported it (Debray et al., 2023; PMID 37650138; Gravel et al., 2021; PMID 32615263) · Dose: 15 minutes after each exercise session, three times a week (Lee et al., 2022; PMID 35785965), or 20 to 30 minutes four times a week (Debray et al., 2023; PMID 37650138) · Population: Sedentary middle-aged adults with a cardiovascular risk factor, adults with stable coronary artery disease, and adults with chronic tension-type headache · Duration: 8 weeks in every multi-week trial · What is sold differs: Home and gym saunas sold as traditional or Finnish vary in temperature, humidity and how much water is thrown on the stones. The observational Kuopio findings come from Finnish men using their own saunas, mostly 2 to 7 times a week; an infrared cabin is a different exposure and is graded separately.
How to track whether this is working
Resting blood pressure and heart rate at baseline and after 8 weeks, the interval the trials used. Session temperature, humidity, minutes per session and sessions per week, so the routine can be set against the studied protocols (about 79 to 81 degrees Celsius, 13 to 23 percent humidity, 15 to 30 minutes, three or four times a week). Fluids taken in and body weight before and after a session.