Table 5: Sauna studies of healthy populations.

Study characteristics Study sample Intervention ComparatorsHealth effectsAdverse side effects
Author & yearLevel of evidenceDesignPop/countrySauna typeDurationComparator/
control
Outcome
measures

2010
Pilch et al. [63]
IITwo group clinical
Interventional study
Healthy females/
Poland
20Finnish2 weeksGroup 1 intervention- sauna × 30 min;
group 2 intervention-sauna × 45 min
HR, SBP, DBP, tympanic temp, rectal temp, wt;
exhaled air analysis for O2 uptake, CO2 exhalation, respiratory quotient; blood analysis for Hb, HCT, calc plasma volume changes, lipid panel, free fatty acids, total free fatty acids – all measured before/after 1st sauna and final sauna
Positive, reduced total cholesterol (), reduced LDL cholesterol ( value unclear), increased HDL cholesterol () claimed (reported numbers do not agree) in group 2 after repeat sauna.None

2008
Kowatzki et al. [64]
II2-group side-by-side clinical
interventional study
Healthy men and women/
Germany
41FinnishMinimum one month of weekly sauna use in “regular sauna group”Two groups receive the same
2-session sauna intervention:
Group 1:“regular sauna group” before intervention
Group 2:
“newcomer sauna group” with no prior sauna 3 months before intervention.
TEWL (trans epidermal water loss); stratum corneum hydration; skin erythema; skin surface pH; surface sebum content; ionic concentration of NaCl in sweatPositive,
baseline values (pre-sauna) of forehead sebum level 25% lower in regular sauna group (); sebum levels decreased similarly in both groups; decrease in NaCl sweat concentration in regular sauna group only (~200 mmol/L to ~170 mmol/L, ); skin surface pH lower in regular sauna group but similar elevations with sauna activity.
None

2007
Pilch et al. [65]
IITwo group clinical interventional studyHealthy
women/
Poland
20Finnish2 weeksGroup 1 intervention- sauna × 30 min;
group 2 intervention-sauna × 45 min
HR, BP, rectal and tympanic temp, body wt; blood Hb; calc plasma volume; serum levels of TSH, T3, T4, human growth hormone, ACTH, cortisolPositive, increased HR, increased SBP, decreased DBP and reduced plasma volumes after single and repeated sauna sessions in both groups (). Increased secretions of growth hormone, ACTH, cortisol after single and repeated sauna sessions in both groups ().None

2014
Gryka et al. [66]
IIISingle group clinical studyHealthy males/
Poland
16Finnish4 weeksNo control groupBody mass, HR, Body skinfold thickness, blood lipid profiles and plasma volumesPositive, reduced total cholesterol (4.50 ± 0.66 mmol/L to 4.18 ± 0.41 mmol/L, ) and LDL levels (2.71 ± 0.47 mmol/L to 2.43 ± 0.35, ) after 10 sessions of sauna over 2 weeks – returned to baseline after 2 weeks without sauna. No significant changes in HDL levelsNone

2014
Pilch et al. [67]
IIISingle group clinical studyHealthy females/
Poland
9Finnish2 weeksNo control groupTympanic temp, rectal temp, wt; plasma levels of Hb, HCT, lipid panel and free fatty acidsPositive, reduction in total cholesterol (4.47 ± 0.85 mmol/L to 4.25 ± 0.93 mmol/L, ) and LDL levels (2.83 ± 0.80 mmol/L to 2.69 ± 0.83 mmol/L, ) after repeated saunaNone

HR = heart rate; SBP = systolic blood pressure; DBP = diastolic blood pressure; temp = body temperature; wt = body weight; Hb = haemoglobin; HCT = haematocrit; calc = calculated; lipid panel = total cholesterol, triglycerides/triacylglycerols, high-density lipoproteins, low-density lipoproteins; NaCl = sodium chloride. ACTH = adrenal corticotrophic hormone.