Table 7: Repeated sauna and male fertility.

Study characteristics Study sample Intervention ComparatorsHealth effectsAdverse side effects
Author & yearLevel of evidenceDesignPop/countrySauna typeDurationComparator/controlsOutcome measuresPositive/negative/negligibleNone/mild/
moderate/
severe

2013
Garolla et al. [27]
IISingle-group, longitudinal time-course studyHealthy males/Italy10Finnish sauna3 monthsNo control groupBefore, after intervention,
after 3 months, after 6 months’ intervention:
semen analysis; plasma sex hormone levels (LH, FSH, testosterone, inhibin); sperm parameters; sperm chromatin structure analysis; sperm apoptosis; sperm heat stress gene expression with quantitative real-time PCR analysis: HIF-1α, KDR, FLT1, VEGF, HSP90, HSP70, HSF1, HSF2, HSFY
NEGATIVE -
Post-intervention: lowered sperm count (93 ± 27.0 × 106 vs 223 ± 52.8 × 106, ); lowered sperm concentration (31 ± 13.1 × 106/ml vs 89 ± 29.3 × 106/ml, ); fewer motile sperm
(36.1 ± 3.6% vs 58.0 ± 7.6%, ) with no differences noted by 6 months post end of sauna intervention.
No significant changes in plasma sex hormones at any timepoints.
Abnormal sperm parameters [decrease in normal histone-protamine replacement (), abnormal chromatin condensation (), altered mitochondrial function ()]; up-regulation of heat-stress genes [ (), KDR (), FLT1 (), VEGF ()] and up-regulation of heat shock proteins/factors [HSP90 (), HSP70 (), HSF1 (), HSF2 (), HSFY ()] directly after sauna intervention but all changes completely reversed by 6 months post ceasing sauna activity.
None

LH = luteinizing hormone; FSH = follicle stimulating hormone; PCR = polymerase chain reaction; HIF-1α = hypoxia-inducible factor I alpha; KDR = kinase insert domain; FLT1 = fms-related tyrosine kinase; VEGF = vascular endothelial growth factor; HSP90 = heat shock protein 90; HSP70 = heat shock protein 70; HSF1 = heat shock factor 1; HSF2 = heat shock factor 2; HSFY = heat shock factor Y.