Table 5.

Sauna studies of healthy populations.

Study characteristics			Study sample		Intervention		Comparators		Health effects	Adverse side effects
Author & year	Level of evidence	Design	Pop/country	N	Sauna type	Duration	Comparator/ control	Outcome measures
2010 Pilch et al. [63]	II	Two group clinical Interventional study	Healthy females/ Poland	20	Finnish	2 weeks	Group 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 (p < 0.05), reduced LDL cholesterol (p value unclear), increased HDL cholesterol (p < 0.05) claimed (reported numbers do not agree) in group 2 after repeat sauna.	None
2008 Kowatzki et al. [64]	II	2-group side-by-side clinical interventional study	Healthy men and women/ Germany	41	Finnish	Minimum 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 sweat	Positive, baseline values (pre-sauna) of forehead sebum level 25% lower in regular sauna group (p < 0.05); sebum levels decreased similarly in both groups; decrease in NaCl sweat concentration in regular sauna group only (~200 mmol/L to ~170 mmol/L, p = 0.0167); skin surface pH lower in regular sauna group but similar elevations with sauna activity.	None
2007 Pilch et al. [65]	II	Two group clinical interventional study	Healthy women/ Poland	20	Finnish	2 weeks	Group 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, cortisol	Positive, increased HR, increased SBP, decreased DBP and reduced plasma volumes after single and repeated sauna sessions in both groups (p < 0.005–p < 0.01). Increased secretions of growth hormone, ACTH, cortisol after single and repeated sauna sessions in both groups (p < 0.01–p < 0.05).	None
2014 Gryka et al. [66]	III	Single group clinical study	Healthy males/ Poland	16	Finnish	4 weeks	No control group	Body mass, HR, Body skinfold thickness, blood lipid profiles and plasma volumes	Positive, reduced total cholesterol (4.50 ± 0.66 mmol/L to 4.18 ± 0.41 mmol/L, p = 0.02) and LDL levels (2.71 ± 0.47 mmol/L to 2.43 ± 0.35, p = 0.01) after 10 sessions of sauna over 2 weeks – returned to baseline after 2 weeks without sauna. No significant changes in HDL levels	None
2014 Pilch et al. [67]	III	Single group clinical study	Healthy females/ Poland	9	Finnish	2 weeks	No control group	Tympanic temp, rectal temp, wt; plasma levels of Hb, HCT, lipid panel and free fatty acids	Positive, reduction in total cholesterol (4.47 ± 0.85 mmol/L to 4.25 ± 0.93 mmol/L, p < 0.05) and LDL levels (2.83 ± 0.80 mmol/L to 2.69 ± 0.83 mmol/L, p < 0.05) after repeated sauna	None

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.