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Research · Practices

Sauna

Finnish cohort studies link sauna bathing 4 to 7 times a week to fewer cardiovascular deaths, strokes and dementia diagnoses. These findings are observational. Pooled heat therapy trials report blood pressure about 4 mmHg lower. An 8-week trial in coronary artery disease found no vascular change. Recorded harms include reversible falls in sperm count, burns, fainting injuries and alcohol-related deaths.

Add to Bio HackChecked 2026-11-13
Status
A practice, not a regulated product.
Also called
Finnish sauna, dry sauna, traditional sauna, sauna bathing, heat therapy, post-exercise sauna
Practiced for
heart health, blood pressure, longevity, endurance, recovery, relaxation, stress, sleep, immunity, colds, dementia, pain, cholesterol, inflammation, detox, weight loss, growth hormone, testosterone

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help12

Reported risks8

What people practice it for, and what was found

Shown to help12

Moderate

Blood pressure

Shown to lower systolic and diastolic blood pressure by about 4 mmHg across heat therapy trials. An 8-week sauna trial in adults with coronary artery disease found no change.

The numbers and sources
Effect
Across 15 studies of repeated heat therapy, systolic pressure fell 3.94 mmHg (95% CI -7.22 to -0.67, 10 studies) and diastolic pressure fell 3.88 mmHg (95% CI -6.13 to -1.63, 9 studies) against control. Resting heart rate did not change [1]. A meta-analysis of 16 sauna articles found systolic and diastolic pressure 5.55 and 6.50 mmHg lower in the 30 minutes after a session, and 5.26 and 4.14 mmHg lower after 2 to 4 weeks of sessions [2]. In 47 sedentary adults, a 15-minute sauna after each exercise session for 8 weeks lowered systolic pressure by 8.0 mmHg (95% CI -14.6 to -1.4) compared with the same exercise alone [3]. In 41 adults with stable coronary artery disease, 4 sauna sessions a week for 8 weeks did not change systolic (P = 0.951) or diastolic pressure (P = 0.292) relative to control [4]. In 16 people with untreated hypertension, the authors report that exercise followed by sauna had positive effects on 24-hour systolic and mean pressure, without giving figures in the abstract [5].
Population
Healthy and clinical populations in 15 studies, 10 to 36 sessions of 30 to 90 minutes [1]. Participants in 16 articles [2]. 47 adults aged 49 on average with low activity and at least one cardiovascular risk factor [3]. 41 adults with coronary artery disease, mean age 62 [4]. 16 people with untreated hypertension [5].
Sources
[1], [2], [3], [4], [5]
Caveats
The pooled review covers heat therapy as a whole, and its abstract does not separate sauna from other heating methods. Certainty was rated moderate for systolic and diastolic pressure [1]. The abstract of [2] does not say how many of its articles were controlled trials. The trial in [3] compared exercise plus sauna against exercise, with no sauna-only group.
Limited

Aerobic fitness when added to exercise

One trial found estimated VO2 max rose 2.7 mL/kg/min more when a 15-minute sauna followed each exercise session for 8 weeks, in 47 sedentary adults.

The numbers and sources
Effect
Estimated VO2 max rose 2.7 mL/kg/min more (95% CI 0.2 to 5.3) with exercise plus sauna than with exercise alone. Exercise alone raised it 6.2 mL/kg/min (95% CI 4.2 to 8.3) over the control group [3].
Population
47 adults aged 49 ± 9 with low physical activity and at least one cardiovascular risk factor, randomized to exercise plus sauna, exercise or control for 8 weeks [3].
Sources
[3]
Caveats
One trial of about 16 people per group. VO2 max was estimated, not measured by gas analysis. There was no sauna-only group.
Limited

Endurance performance in trained runners

Small trials found longer run time to exhaustion and higher VO2 max in trained runners after 3 weeks of post-training sauna sessions.

The numbers and sources
Effect
In 6 male distance runners, 3 weeks of post-training sauna increased run time to exhaustion by 32% (90% confidence limits 21 to 43%) relative to control training, which the authors equate to about 1.9% in an endurance time trial. Plasma volume rose 7.1% [6]. In 20 middle-distance runners, 3 weeks of post-exercise sauna raised VO2 max by 0.27 L/min (p = 0.02) and running speed at 4 mmol/L blood lactate by 0.6 km/h (p = 0.01) more than training alone [7]. In 26 runners who all used the sauna, VO2 max rose 5% in both women and men [8].
Population
6 competitive male runners in a crossover study [6]. 20 trained runners, 13 of them women, mean age 20 [7]. 26 trained runners, 16 of them women [8].
Sources
[6], [7], [8]
Caveats
Very small samples. The abstract of [7] does not say that groups were randomized, and [8] had no control group. Sessions were about 30 minutes at 90°C to 108°C straight after training.
Limited

Death from heart disease

Linked to fewer cardiovascular deaths in Finnish cohorts, with a hazard ratio of 0.37 for sudden cardiac death at 4 to 7 sessions a week against one.

The numbers and sources
Effect
In 2,315 Finnish men followed for a median 20.7 years, fatal cardiovascular disease occurred in 22.3% of men using a sauna once a week, 16.4% at 2 to 3 times and 12.0% at 4 to 7 times. The adjusted hazard ratio for sudden cardiac death was 0.78 (95% CI 0.57 to 1.07) at 2 to 3 sessions a week and 0.37 (95% CI 0.18 to 0.75) at 4 to 7 sessions. Sessions longer than 19 minutes carried a hazard ratio of 0.48 (95% CI 0.31 to 0.75) against sessions under 11 minutes [9]. In 1,688 men and women followed for 15.0 years, adjusted hazard ratios for cardiovascular death were 0.75 (95% CI 0.52 to 1.08) and 0.23 (95% CI 0.08 to 0.65) [10]. In 2,277 men over 26.1 years, 3 to 7 sessions a week against 2 or fewer carried a hazard ratio of 0.74 (95% CI 0.59 to 0.94) for cardiovascular death [11].
Population
Men aged 42 to 60 from eastern Finland in the Kuopio Ischemic Heart Disease study [9][11]. 1,688 participants with a mean age of 63, 51.4% women [10].
Sources
[9], [10], [11]
Caveats
Observational. All three analyses come from one Finnish cohort program and one research group, and sauna habits were self-reported at baseline. Only 201 men were in the 4 to 7 sessions group, with 10 sudden cardiac deaths [9]. The link may reflect other differences between frequent and infrequent sauna users.
LimitedStudied in men

Death from any cause

Linked to lower all-cause mortality in Finnish men, with a hazard ratio of about 0.85 for 3 to 7 sessions a week against 2 or fewer.

The numbers and sources
Effect
Over 20.7 years, 49.1% of men using a sauna once a week died, against 37.8% at 2 to 3 times and 30.8% at 4 to 7 times, with a significant trend after adjustment (P for trend 0.005 or less). Session length was not associated with all-cause mortality [9]. Comparing 3 to 7 sessions a week with 2 or fewer, adjusted hazard ratios for death from any cause were 0.84 (95% CI 0.72 to 0.97) in 2,277 men [11] and 0.86 (95% CI 0.76 to 0.97) in 2,575 men followed for 27.8 years [12].
Population
Finnish men aged 42 to 61 at baseline in the Kuopio Ischemic Heart Disease study [9][11][12].
Sources
[9], [11], [12]
Caveats
Observational, and all three analyses use the same cohort of Finnish men. No randomized trial has measured mortality.
Limited

Stroke

Linked to fewer strokes in Finnish men and women, with a hazard ratio of 0.38 at 4 to 7 sessions a week against one.

The numbers and sources
Effect
During a median 14.9 years, 155 strokes occurred. Compared with one session a week, 4 to 7 sessions carried a hazard ratio of 0.38 (95% CI 0.18 to 0.81) after adjustment for cardiovascular risk factors, physical activity and socioeconomic status [13].
Population
1,628 men and women aged 53 to 74 with no history of stroke, in the Kuopio Ischemic Heart Disease study [13].
Sources
[13]
Caveats
Observational, one cohort. Only 34 hemorrhagic strokes occurred, and the association there was described as modest [13].
LimitedStudied in men

New high blood pressure

Linked to fewer new cases of hypertension in Finnish men, with a hazard ratio of 0.53 at 4 to 7 sessions a week against one.

The numbers and sources
Effect
Over a median 24.7 years, 251 of 1,621 men (15.5%) developed hypertension. After adjustment, hazard ratios were 0.83 (95% CI 0.59 to 1.18) at 2 to 3 sessions a week and 0.53 (95% CI 0.28 to 0.98) at 4 to 7 sessions, compared with one [14].
Population
1,621 men aged 42 to 60 without hypertension at baseline [14].
Sources
[14]
Caveats
Observational, one cohort of men. The upper confidence limit sits close to 1.
Limited

Dementia and Alzheimer's disease

Linked to fewer dementia diagnoses in two Finnish cohorts, with hazard ratios of 0.34 and 0.81 for the most frequent users in each.

The numbers and sources
Effect
In 2,315 men followed for 20.7 years, 204 developed dementia and 123 Alzheimer's disease. Against one session a week, hazard ratios for dementia were 0.78 (95% CI 0.57 to 1.06) at 2 to 3 sessions and 0.34 (95% CI 0.16 to 0.71) at 4 to 7 sessions. For Alzheimer's disease they were 0.80 (95% CI 0.53 to 1.20) and 0.35 (95% CI 0.14 to 0.90) [15]. In 13,994 men and women followed for 39 years with 1,805 dementia diagnoses, sauna bathing 9 to 12 times a month against under 4 times carried a hazard ratio of 0.47 (95% CI 0.25 to 0.88) in the first 20 years and 0.81 (95% CI 0.69 to 0.97) over the whole follow-up [16].
Population
Finnish men aged 42 to 60 [15]. Finnish men and women aged 30 to 69 in the Mobile Clinic Follow-up Survey [16].
Sources
[15], [16]
Caveats
Observational. The two cohorts are independent of each other, and the association weakened over longer follow-up in the larger one [16].
LimitedStudied in men

Pneumonia and respiratory disease

Linked to fewer hospital diagnoses of pneumonia and other respiratory disease in Finnish men who used a sauna 2 or more times a week.

The numbers and sources
Effect
Over 25.6 years, 379 of 1,935 men had a hospital diagnosis of chronic obstructive pulmonary disease, asthma or pneumonia. Against one session a week or fewer, hazard ratios were 0.73 (95% CI 0.58 to 0.92) at 2 to 3 sessions and 0.59 (95% CI 0.37 to 0.94) at 4 or more [17]. For pneumonia alone, in 2,210 men with 375 cases, the fully adjusted hazard ratios were 0.72 (95% CI 0.57 to 0.90) and 0.63 (95% CI 0.39 to 1.00) [18].
Population
Finnish men aged 42 to 61 [17][18].
Sources
[17], [18]
Caveats
Observational, and both analyses use the same cohort. Only men were studied.
Limited

Common colds

One trial found fewer colds over 6 months in 25 people who took regular saunas than in 25 who did not. Duration and severity did not differ.

The numbers and sources
Effect
The sauna group had significantly fewer episodes of common cold over 6 months. In the last 3 months the incidence was roughly half that of controls. Mean duration and severity of colds did not differ between groups [19].
Population
50 volunteers, 25 taking regular saunas and 25 abstaining, followed for 6 months [19].
Sources
[19]
Caveats
One small trial from 1990. The abstract gives no exact counts and does not say that allocation was randomized or that anyone was blinded.
Limited

Chronic tension-type headache

One trial found headache intensity fell 1.27 points more on a pain scale with 8 weeks of regular sauna in 37 people. Headache duration did not change.

The numbers and sources
Effect
Mean change in headache intensity on a numerical pain rating scale differed between sauna and control by 1.27 points (95% CI 0.48 to 2.07, p = 0.002). Headache duration, sleep disturbance, depression and headache disability did not differ between groups [20].
Population
37 people with chronic tension-type headache, 17 assigned to sauna plus advice and 20 to advice alone, for 8 weeks [20].
Sources
[20]
Caveats
One small unblinded trial.
Limited

Low back pain

Limited evidence: pain scores fell from a median of 5 to 3 in 37 people after 10 sauna sessions, in a study with no control group.

The numbers and sources
Effect
After 10 sessions of 15 minutes at 90°C over 5 days, median pain on a verbal numerical rating scale fell from 5 (range 2 to 8) to 3 (range 0 to 8), and median Oswestry disability scores fell from 12 to 8 (P < 0.001 for both) [21].
Population
37 consecutive patients over 20 years of age with low back pain [21].
Sources
[21]
Caveats
No control group, so the change cannot be separated from natural recovery or expectation. One week of follow-up.

Mixed results8

Moderate

Blood vessel function

Mixed results: pooled heat therapy trials found better artery dilation, while two 8-week sauna trials found no change in artery dilation or stiffness.

The numbers and sources
Effect
Heat therapy improved brachial artery flow-mediated dilation by 1.95 percentage points (95% CI 0.14 to 3.76, 5 studies) [1]. A sauna meta-analysis reported flow-mediated dilation 1.71 percentage points higher after 2 to 4 weeks [2]. In adults with stable coronary artery disease, 8 weeks of Finnish sauna did not change flow-mediated dilation (0.15% with sauna, 0.07% with control, interaction P = 0.909) or carotid-femoral pulse wave velocity (P = 0.816) [4]. In sedentary adults, pulse wave velocity did not differ between exercise plus sauna and exercise alone (-0.4 m/s, 95% CI -1.1 to 0.3) [3].
Population
Healthy and clinical populations [1][2]. 41 adults with coronary artery disease, 21 assigned to sauna at 79°C for 20 to 30 minutes, 4 times a week [4]. 47 sedentary adults [3].
Sources
[1], [2], [4], [3]
Caveats
Certainty was rated low for flow-mediated dilation [1]. In [4] the sauna group showed signs of heat acclimation, a lower resting core temperature and a higher sweat rate, without vascular change.
Limited

Cholesterol

Mixed results: 4 trials in adults under 60 found lower total and LDL cholesterol with hot spring or sauna use, and 3 trials in older adults found no change.

The numbers and sources
Effect
A systematic review of 7 RCTs found reductions in total and LDL cholesterol in 4 trials with a mean age under 60, and no significant lipid changes in 3 trials with a mean age of 60 or more [22]. In sedentary adults, total cholesterol fell 19 mg/dL more (95% CI -35 to 0) with exercise plus sauna than with exercise alone over 8 weeks [3].
Population
Adults in 7 RCTs of hot spring or sauna use, alone or with exercise [22]. 47 sedentary adults [3].
Sources
[22], [3]
Caveats
The review pools hot springs with saunas and reports no pooled effect size [22]. The confidence interval in [3] reaches zero.
LimitedStudied in men

Inflammation markers

Mixed results: frequent sauna users had lower C-reactive protein in a study of 2,084 Finnish men, while a 4-week trial in 15 men found no change.

The numbers and sources
Effect
Mean C-reactive protein was 2.41, 2.00 and 1.65 in men using a sauna once, 2 to 3 times and 4 to 7 times a week, an inverse association that held after adjustment [23]. In 15 untrained young men randomized to cycling 3 times a week with or without a 30-minute sauna afterward, high-sensitivity C-reactive protein did not differ between groups after 4 weeks. Gut bacteria and intestinal barrier markers did not differ either [24].
Population
2,084 Finnish men aged 42 to 60 without acute or chronic inflammation, measured once [23]. 15 men aged 22 on average [24].
Sources
[23], [24]
Caveats
The larger study is cross-sectional, a single measurement that cannot show sauna use came first. Its abstract gives the unit as mmol/L, and C-reactive protein is usually reported in mg/L, so the unit may be a reporting error [23]. The trial was a pilot [24].
Limited

Recovery after hard training

Mixed results: swimmers were slower the morning after a post-training sauna, while a sauna before eccentric exercise reduced strength and motion losses in one small trial.

The numbers and sources
Effect
In 20 competitive swimmers and triathletes, a 4 x 50 m all-out swim the next morning was 1.69 s slower after 3 x 8 minutes of sauna at 80°C to 85°C, against 0.66 s faster after a placebo treatment (P = .02). Perceived stress was higher after sauna [25]. In 28 young adults, a sauna before eccentric wrist exercise led to smaller deficits in range of motion, grip strength and wrist extension strength than no sauna (P < 0.05) [26].
Population
20 swimmers and triathletes in a randomized crossover [25]. 28 adults with a mean age of 20.9, randomized to sauna or control [26].
Sources
[25], [26]
Caveats
Two small trials asking different questions, one of sauna after training and one of sauna before it. The authors of [25] put the smallest meaningful change in this swim test at 1.2 s.
Limited

Growth hormone

Limited evidence: growth hormone rose 16-fold in 10 men during a week of twice-daily one-hour saunas, and the response declined after the third day.

The numbers and sources
Effect
In 10 healthy men exposed to an 80°C sauna for 1 hour twice a day for 7 days, serum growth hormone rose 16-fold and prolactin 2.3-fold (P < 0.01). The growth hormone response declined after the third day. Cortisol and ACTH fell slightly by the end [28].
Population
10 healthy men, with 7 women taking part in prolactin measurements only [28].
Sources
[28]
Caveats
One 1986 study with no control group. Two hours a day at 80°C is far longer than the sessions in other studies here. No muscle, recovery or body composition outcome was measured. The authors suggest dehydration may explain the hormone release.
Limited

Sleep

Mixed results: 83.5% of surveyed sauna users reported sleep benefits, while an 8-week trial in people with chronic headache found no change in sleep disturbance.

The numbers and sources
Effect
In an online survey of 482 regular sauna users, 83.5% reported sleep benefits after sauna use [30]. In a randomized trial in chronic tension-type headache, sleep disturbance did not differ between the sauna and control groups after 8 weeks [20].
Population
482 survey respondents who used a sauna about 1 to 2 times a week [30]. 37 people with chronic tension-type headache [20].
Sources
[30], [20]
Caveats
The survey is self-selected and self-reported, with no comparison group [30]. Sleep was a secondary outcome of the headache trial, and no trial measuring sleep with instruments was located.
LimitedStudied in men

Blood clots in veins

Mixed results: Finnish men using a sauna 2 to 3 times a week had fewer venous clots than men using it once, and men at 4 or more did not.

The numbers and sources
Effect
Over 24.9 years, 146 of 2,242 men (6.5%) had a venous thromboembolism. Against one session a week or fewer, adjusted hazard ratios were 0.67 (95% CI 0.46 to 0.96) at 2 to 3 sessions and 0.92 (95% CI 0.51 to 1.68) at 4 or more [32].
Population
2,242 Finnish men aged 42 to 61 with no history of venous thromboembolism [32].
Sources
[32]
Caveats
Observational, one cohort. The most frequent users showed no association, so there is no dose pattern.
Limited

Sweating out heavy metals

Limited evidence: arsenic, cadmium, lead and mercury have been measured in sweat, and the reviewers call for properly sized trials before conclusions about lowering body levels.

The numbers and sources
Effect
A systematic review of 24 studies found that in people with higher exposure, sweat concentrations of these metals generally exceeded plasma or urine concentrations. Populations, collection methods and concentrations varied widely. The one sauna finding named in the abstract is a case report in which mercury levels normalized with repeated saunas [34].
Population
People with and without known metal exposure in 24 studies of sweat [34].
Sources
[34]
Caveats
The studies measured what is in sweat. None in the abstract measured a health outcome, and the authors state that appropriately sized trials are needed [34].

Not shown to help4

Limited

Fat loss

One trial found no added fat loss when a sauna followed exercise for 8 weeks. Body mass lost during a sauna session was studied as fluid to be replaced.

The numbers and sources
Effect
Fat mass changed by -0.6 kg (95% CI -1.9 to 0.7, P = 0.339) with exercise plus sauna compared with exercise alone. Exercise alone lowered fat mass by 1.3 kg against control [3]. In 674 sedentary students, body mass lost over two 10-minute dry sauna sessions rose with body mass index, and the authors used it to estimate the fluid to be replaced [27].
Population
47 sedentary adults over 8 weeks [3]. 326 women and 348 men aged 19 to 20 in a single visit [27].
Sources
[3], [27]
Caveats
Fat mass was a secondary outcome in a small trial [3]. The student study measured weight change across one visit, not body fat [27].
LimitedStudied in men

Testosterone

Small studies found no change in testosterone or other sex hormones in men, after 7 days of intensive sauna use or 3 months of twice-weekly sessions.

The numbers and sources
Effect
Testosterone, FSH and LH did not change significantly in 10 men over 7 days of twice-daily one-hour saunas [28]. In 10 men taking two 15-minute sessions a week at 80°C to 90°C for 3 months, sex hormones did not change significantly [29].
Population
10 healthy men [28]. 10 men with normal sperm counts [29].
Sources
[28], [29]
Caveats
Two studies of 10 men each, neither with a control group.
Limited

Heart rate variability

One trial found no added change in heart rate variability when a 15-minute sauna followed exercise for 8 weeks, compared with exercise alone.

The numbers and sources
Effect
No heart rate variability index differed significantly between exercise plus sauna and exercise alone after 8 weeks, including RMSSD, SDNN and resting heart rate [31].
Population
38 sedentary adults aged 49 ± 9 with at least one cardiovascular risk factor, in three groups [31].
Sources
[31], [3]
Caveats
One small trial, drawn from the same study as the blood pressure and fitness findings in [3].
LimitedStudied in men

Urinary symptoms in men

Not linked to the development or course of lower urinary tract symptoms in 1,306 Finnish men followed for 10 years.

The numbers and sources
Effect
Sauna frequency showed no clear association with the prevalence, incidence or remission of 9 of 10 urinary symptoms, or with medication or surgery for them. Feelings of incomplete emptying were less common with frequent sauna use [33].
Population
1,306 men aged 50, 60 or 70 in 1994 who answered questionnaires in 1994, 1999 and 2004 [33].
Sources
[33]
Caveats
Observational. Of 3,163 men invited, 41.3% answered all three rounds.

Protocols studied

The Finnish cohorts sorted people by what they reported at baseline: 1, 2 to 3, or 4 to 7 sessions a week, and sessions under 11, 11 to 19, or over 19 minutes [9]. The trial in coronary artery disease used 79°C at 13% relative humidity for 20 to 30 minutes, 4 times a week for 8 weeks [4]. The exercise trial added 15 minutes after each of 3 weekly workouts for 8 weeks, starting at 65°C and rising 5°C every two weeks [3]. Pooled heat therapy trials used 30 to 90 minutes per exposure over 10 to 36 sessions [1].

Runner studies used about 30 minutes straight after training, roughly 3 times a week for 3 weeks, at 90°C in a humid sauna [6] or at 101°C to 108°C [7]. The sperm study used 15 minutes at 80°C to 90°C twice a week for 3 months [29]. The low back pain study used 15 minutes at 90°C twice a day for 5 days [21]. The growth hormone study used 1 hour at 80°C twice a day for 7 days [28].

Risks

Reported risks8

LimitedStudied in men

Sperm count and motility

One small study found sperm count and motility fell after 3 months of twice-weekly saunas in 10 men, and recovered fully within 6 months of stopping.

The numbers and sources
Effect
After two 15-minute sessions a week at 80°C to 90°C for 3 months, sperm count and motility were strongly impaired (P < 0.001). The share of sperm with normal mitochondrial function fell from 76.8% to 54.0%, and with normal chromatin condensation from 70.7% to 63.6%. Sex hormones did not change. All effects had reversed 6 months after the sessions ended [29].
Population
10 men with normal sperm counts at the start [29].
Sources
[29], [35]
Caveats
Ten men, no control group, and none had abnormal sperm at baseline. A systematic review of 40 sauna studies with 3,855 participants found this was the only study reporting an adverse health outcome [35]. Fertility itself was not measured.
Limited

Deaths in the sauna

Case series: sauna deaths in Finland ran below 2 per 100,000 people a year, and half or more of those who died had been drinking alcohol.

The numbers and sources
Effect
In Finland from 1990 to 2002, deaths occurring in a sauna numbered fewer than 2 per 100,000 inhabitants a year. About half (51%) were natural deaths, heat exposure was the cause in 25%, and 50% of all cases were under the influence of alcohol [36]. In Sweden from 1992 to 2003, 77 sauna deaths were identified, 82% of them men. Of 69 with blood alcohol measured, 49 (71%) tested positive. Of those found dead in a sauna, all but 2 were alone [37].
Population
Forensic autopsy records for Finland, 1990 to 2002 [36], and Sweden, 1992 to 2003 [37].
Sources
[36], [37]
Caveats
Autopsy series count deaths that happened in a sauna. They cannot show how many would have happened elsewhere, and they give no rate per session.
LimitedStudied in men

Low blood pressure with alcohol

One small study found systolic blood pressure fell from 136 to 113 mmHg when 10 men combined heavy drinking with a sauna, and not with sauna alone.

The numbers and sources
Effect
In 10 healthy men, systolic pressure stayed at baseline during a sauna without alcohol and fell from 136 to 113 mmHg with sauna after heavy drinking (P < 0.01). Heart rate rose equally in both conditions. Neither condition increased premature ventricular beats [38].
Population
10 healthy male volunteers [38].
Sources
[38]
Caveats
One small study in healthy young men, so it says nothing about people with heart disease.
Limited

Falls and fainting injuries

Case series: among 209 people treated for sauna injuries at one trauma center, 57.5% of injuries followed a slip or fall and 30.0% followed dizziness or fainting.

The numbers and sources
Effect
Over 17 years, 209 patients had 274 diagnoses, including bruises and sprains (41.2%), wounds (28.8%), fractures (15.3%), concussions (5.5%), burns (1.5%) and brain bleeding (1.1%). Head and face injuries mostly followed dizziness or fainting. Nine patients (4.3%) needed surgery [39].
Population
209 patients treated at the trauma center of the Medical University of Innsbruck, 2005 to 2021 [39].
Sources
[39]
Caveats
One hospital, with no count of how many sauna visits these injuries came from.
Limited

Burns

Case series: a Finnish burn center attributed one in four of its burn patients to the sauna, and 54% of those burns needed surgery.

The numbers and sources
Effect
Of 598 burn patients treated over 7 years, 154 had sauna-related burns. Most were minor, 54% required operative treatment, 71% of patients were men and 40% were under the influence of alcohol. The author estimates 7 sauna-related burns per 100,000 people a year in Finland [40].
Population
154 patients at Kuopio University Hospital Burn Center, 1994 to 2000 [40].
Sources
[40]
Caveats
One burn center in a country where most homes have a sauna, so the rate does not transfer to other countries.
Limited

Reduced blood flow to the heart in coronary artery disease

One small study found heart muscle perfusion scans were worse during a sauna than at rest in 14 of 15 people with coronary artery disease, without symptoms.

The numbers and sources
Effect
In people with proven coronary artery disease, perfusion defect scores averaged -0.93 in the sauna against -0.44 at rest (P < 0.001), and were worse than rest in 14 of 15. Heart rate rose 32% and systolic pressure fell 13%. There were no arrhythmias or ECG changes, and the session was clinically tolerated [41].
Population
16 patients with coronary artery disease, 15 with perfusion scores [41].
Sources
[41], [4]
Caveats
One small imaging study from 1999. A later trial gave 21 adults with stable coronary artery disease 4 sauna sessions a week for 8 weeks, and its abstract does not report on cardiac events either way [4].
LimitedStudied in women

Missed periods after intensive use

One small study found prolactin rose more than four-fold and 5 of 7 women had temporarily absent periods after a week of twice-daily one-hour saunas.

The numbers and sources
Effect
In 7 women exposed to an 80°C sauna for 1 hour twice a day for 7 days, serum prolactin rose more than four-fold (P < 0.01). Transient amenorrhea occurred in 5 of the 7 after the experiment, which the authors suggest may be associated with the prolactin release [28].
Population
7 healthy women [28].
Sources
[28]
Caveats
Seven women, no control group, and an exposure of 2 hours a day that is far beyond the sessions used in other studies.
Limited

Side effects reported by sauna users

In a survey of 482 regular sauna users, reported adverse reactions were mostly minor, chiefly dizziness, dehydration and headache. Two reports involved hospital care.

The numbers and sources
Effect
Adverse reactions were recorded as mostly minor (93.1%), primarily dizziness, dehydration and headache. Two reports, of chest pain and of eye irritation, required hospitalization [30]. A systematic review of 40 clinical studies with 3,855 participants found one study reporting an adverse outcome and called for better data on the frequency of side effects [35].
Population
482 survey respondents [30]. Participants in 40 studies of repeated dry sauna, 13 of them randomized [35].
Sources
[30], [35]
Caveats
The survey reached current sauna users, so people who stopped because of side effects are missing. Most studies in the review had fewer than 40 participants and did not collect side effects systematically [35].

Checked, no increase found2

Moderate

Core temperature in pregnancy

No pregnant woman reached a core temperature of 39.0°C across 12 studies of exercise, hot baths and sauna. Mean core temperature after sauna was 37.6°C.

The numbers and sources
Effect
A systematic review of 12 studies (347 pregnant women) found the highest individual core temperature was 38.9°C, during land-based exercise. The highest mean end-of-trial core temperature for sauna exposure was 37.6°C (95% CI 37.5 to 37.7), in sessions of up to 20 minutes at 70°C and 15% relative humidity [42].
Population
347 pregnant women at any stage of pregnancy in 12 studies [42].
Sources
[42]
Caveats
The studies measured core temperature against a proposed threshold of 39.0°C, not birth outcomes. Sauna exposures were no longer than 20 minutes and no hotter than 70°C, cooler than many of the protocols on this page.
LimitedStudied in men

Kidney function

Not linked to chronic kidney disease in 2,071 Finnish men followed for a median 25.7 years.

The numbers and sources
Effect
Comparing 4 to 7 sessions a week with one, estimated glomerular filtration rate, creatinine and sodium did not differ at baseline, and potassium was 0.05 mmol/L higher. Over 25.7 years, 188 men developed chronic kidney disease, with a hazard ratio of 0.84 (95% CI 0.46 to 1.53) [43].
Population
2,071 men aged 42 to 61 with normal kidney function at baseline [43].
Sources
[43]
Caveats
Observational, one cohort of men, with a wide confidence interval.

Claims tested and not found

  1. That regular sauna use improves artery function in people with coronary artery disease. Eight weeks of 4 sessions a week did not change flow-mediated dilation, arterial stiffness or blood pressure against control in 41 adults [4].
  2. That adding a sauna after exercise improves heart rate variability. No index differed from exercise alone after 8 weeks [31].
  3. That adding a sauna after exercise burns more fat. Fat mass did not differ from exercise alone after 8 weeks (-0.6 kg, 95% CI -1.9 to 0.7) [3].
  4. That sauna raises testosterone. Testosterone did not change in two studies of 10 men each [28][29].
  5. That a sauna after hard training speeds next-day recovery. Swimmers were 1.69 s slower over 4 x 50 m the morning after a post-training sauna, against 0.66 s faster after placebo [25].
  6. That sauna use lowers C-reactive protein within weeks. A 4-week randomized pilot in 15 men found no difference from exercise alone [24].

Sources

  1. Pizzey FK, Smith EC, Ruediger SL, et al. The effect of heat therapy on blood pressure and peripheral vascular function: A systematic review and meta-analysis. Experimental Physiology. 2021. https://doi.org/10.1113/ep089424
  2. Li Z, Jiang W, Chen Y, et al. Acute and short-term efficacy of sauna treatment on cardiovascular function: A meta-analysis. European Journal of Cardiovascular Nursing. 2020. https://doi.org/10.1177/1474515120944584
  3. Lee E, Kolunsarka I, Kostensalo J, et al. Effects of regular sauna bathing in conjunction with exercise on cardiovascular function: a multi-arm, randomized controlled trial. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 2022. https://doi.org/10.1152/ajpregu.00076.2022
  4. Debray A, Gravel H, Garceau L, et al. Finnish sauna bathing and vascular health of adults with coronary artery disease: a randomized controlled trial. Journal of Applied Physiology. 2023. https://doi.org/10.1152/japplphysiol.00322.2023
  5. Gayda M, Paillard F, Sosner P, et al. Effects of Sauna Alone and Postexercise Sauna Baths on Blood Pressure and Hemodynamic Variables in Patients With Untreated Hypertension. The Journal of Clinical Hypertension. 2012. https://doi.org/10.1111/j.1751-7176.2012.00637.x
  6. Scoon GS, Hopkins WG, Mayhew S, Cotter JD. Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. Journal of Science and Medicine in Sport. 2007. https://doi.org/10.1016/j.jsams.2006.06.009
  7. Kirby NV, Lucas SJE, Armstrong OJ, et al. Intermittent post-exercise sauna bathing improves markers of exercise capacity in hot and temperate conditions in trained middle-distance runners. European Journal of Applied Physiology. 2021. https://doi.org/10.1007/s00421-020-04541-z
  8. Kirby NV, Lucas SJE, Cable TG, et al. Sex differences in adaptation to intermittent post-exercise sauna bathing in trained middle-distance runners. Sports Medicine - Open. 2021. https://doi.org/10.1186/s40798-021-00342-6
  9. Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events. JAMA Internal Medicine. 2015. https://doi.org/10.1001/jamainternmed.2014.8187
  10. Laukkanen T, Kunutsor SK, Khan H, et al. Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study. BMC Medicine. 2018. https://doi.org/10.1186/s12916-018-1198-0
  11. Kunutsor SK, Khan H, Laukkanen T, Laukkanen JA. Joint associations of sauna bathing and cardiorespiratory fitness on cardiovascular and all-cause mortality risk: a long-term prospective cohort study. Annals of Medicine. 2018. https://doi.org/10.1080/07853890.2017.1387927
  12. Kunutsor SK, Jae SY, Kurl S, et al. Inflammation, sauna bathing, and all-cause mortality in middle-aged and older Finnish men: a cohort study. European Journal of Epidemiology. 2022. https://doi.org/10.1007/s10654-022-00926-w
  13. Kunutsor SK, Khan H, Zaccardi F, et al. Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort study. Neurology. 2018. https://doi.org/10.1212/wnl.0000000000005606
  14. Zaccardi F, Laukkanen T, Willeit P, et al. Sauna Bathing and Incident Hypertension: A Prospective Cohort Study. American Journal of Hypertension. 2017. https://doi.org/10.1093/ajh/hpx102
  15. Laukkanen T, Kunutsor S, Kauhanen J, Laukkanen JA. Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men. Age and Ageing. 2017. https://doi.org/10.1093/ageing/afw212
  16. Knekt P, Järvinen R, Rissanen H, et al. Does sauna bathing protect against dementia? Preventive Medicine Reports. 2020. https://doi.org/10.1016/j.pmedr.2020.101221
  17. Kunutsor SK, Laukkanen T, Laukkanen JA. Sauna bathing reduces the risk of respiratory diseases: a long-term prospective cohort study. European Journal of Epidemiology. 2017. https://doi.org/10.1007/s10654-017-0311-6
  18. Kunutsor SK, Laukkanen T, Laukkanen JA. Frequent sauna bathing may reduce the risk of pneumonia in middle-aged Caucasian men: The KIHD prospective cohort study. Respiratory Medicine. 2017. https://doi.org/10.1016/j.rmed.2017.10.018
  19. Ernst E, Pecho E, Wirz P, Saradeth T. Regular Sauna Bathing and the Incidence of Common Colds. Annals of Medicine. 1990. https://doi.org/10.3109/07853899009148930
  20. Kanji G, Weatherall M, Peter R, et al. Efficacy of Regular Sauna Bathing for Chronic Tension-Type Headache: A Randomized Controlled Study. The Journal of Alternative and Complementary Medicine. 2015. https://doi.org/10.1089/acm.2013.0466
  21. Cho EH, Kim NH, Kim HC, et al. Dry sauna therapy is beneficial for patients with low back pain. Anesthesia and Pain Medicine. 2019. https://doi.org/10.17085/apm.2019.14.4.474
  22. Yamasaki S, Tokunou T, Kashiwado Y, et al. Hot spring and sauna use for improving blood lipid profiles: A systematic review and expert consensus on efficacy and recommendations. Complementary Therapies in Medicine. 2025. https://doi.org/10.1016/j.ctim.2025.103241
  23. Laukkanen JA, Laukkanen T. Sauna bathing and systemic inflammation. European Journal of Epidemiology. 2018. https://doi.org/10.1007/s10654-017-0335-y
  24. Karolkiewicz J, Nieman DC, Cisoń T, et al. No effects of a 4-week post-exercise sauna bathing on targeted gut microbiota and intestinal barrier function, and hsCRP in healthy men: a pilot randomized controlled trial. BMC Sports Science, Medicine and Rehabilitation. 2022. https://doi.org/10.1186/s13102-022-00497-z
  25. Skorski S, Schimpchen J, Pfeiffer M, et al. Effects of Postexercise Sauna Bathing on Recovery of Swim Performance. International Journal of Sports Physiology and Performance. 2020. https://doi.org/10.1123/ijspp.2019-0333
  26. Khamwong P, Paungmali A, Pirunsan U, Joseph L. Prophylactic Effects of Sauna on Delayed-Onset Muscle Soreness of the Wrist Extensors. Asian Journal of Sports Medicine. 2015. https://doi.org/10.5812/asjsm.6(2)2015.25549
  27. Podstawski R, Boraczyński T, Boraczyński M, et al. Sauna-induced body mass loss in young sedentary women and men. The Scientific World Journal. 2014. https://doi.org/10.1155/2014/307421
  28. Leppäluoto J, Huttunen P, Hirvonen J, et al. Endocrine effects of repeated sauna bathing. Acta Physiologica Scandinavica. 1986. https://doi.org/10.1111/j.1748-1716.1986.tb08000.x
  29. Garolla A, Torino M, Sartini B, et al. Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Human Reproduction. 2013. https://doi.org/10.1093/humrep/det020
  30. Hussain JN, Greaves RF, Cohen MM. A hot topic for health: Results of the Global Sauna Survey. Complementary Therapies in Medicine. 2019. https://doi.org/10.1016/j.ctim.2019.03.012
  31. Lee E, Ketelhut S, Wiklund P, et al. Regular postexercise sauna bathing does not improve heart rate variability: A multi-arm randomized controlled trial. Physiological Reports. 2025. https://doi.org/10.14814/phy2.70449
  32. Kunutsor SK, Mäkikallio TH, Khan H, et al. Sauna bathing reduces the risk of venous thromboembolism: a prospective cohort study. European Journal of Epidemiology. 2019. https://doi.org/10.1007/s10654-019-00544-z
  33. Pöyhönen A, Åkerla J, Koskimäki J, et al. Sauna habits/bathing and changes in lower urinary tract symptoms, Tampere Ageing Male Urologic Study (TAMUS). Scandinavian Journal of Urology. 2022. https://doi.org/10.1080/21681805.2021.2002403
  34. Sears ME, Kerr KJ, Bray RI. Arsenic, Cadmium, Lead, and Mercury in Sweat: A Systematic Review. Journal of Environmental and Public Health. 2012. https://doi.org/10.1155/2012/184745
  35. Hussain J, Cohen M. Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review. Evidence-Based Complementary and Alternative Medicine. 2018. https://doi.org/10.1155/2018/1857413
  36. Kenttämies A, Karkola K. Death in Sauna. Journal of Forensic Sciences. 2008. https://doi.org/10.1111/j.1556-4029.2008.00703.x
  37. Rodhe A, Eriksson A. Sauna Deaths in Sweden, 1992 to 2003. American Journal of Forensic Medicine and Pathology. 2008. https://doi.org/10.1097/paf.0b013e318145ae05
  38. Roine R, Luurila OJ, Suokas A, et al. Alcohol and sauna bathing: effects on cardiac rhythm, blood pressure, and serum electrolyte and cortisol concentrations. Journal of Internal Medicine. 1992. https://doi.org/10.1111/j.1365-2796.1992.tb00941.x
  39. Kaiser P, Seeher U, Krasniqi A, et al. Injuries related to sauna bathing. Injury. 2023. https://doi.org/10.1016/j.injury.2023.05.056
  40. Papp A. Sauna-related burns: a review of 154 cases treated in Kuopio University Hospital Burn Center 1994 to 2000. Burns. 2002. https://doi.org/10.1016/s0305-4179(01)00073-0
  41. Giannetti N, Juneau M, Arsenault A, et al. Sauna-induced myocardial ischemia in patients with coronary artery disease. The American Journal of Medicine. 1999. https://doi.org/10.1016/s0002-9343(99)00220-x
  42. Ravanelli N, Casasola W, English T, et al. Heat stress and fetal risk. Environmental limits for exercise and passive heat stress during pregnancy: a systematic review with best evidence synthesis. British Journal of Sports Medicine. 2019. https://doi.org/10.1136/bjsports-2017-097914
  43. Kunutsor SK, Kauhanen J, Laukkanen JA. Sauna bathing, renal function and chronic kidney disease: Cross-sectional and longitudinal findings from the KIHD study. European Journal of Clinical Investigation. 2023. https://doi.org/10.1111/eci.14001

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