Sauna bathing, renal function and chronic kidney disease: Cross‐sectional and longitudinal findings from the KIHD study

Abstract

Background: It is uncertain if passive heat therapies are associated with adverse renal outcomes. We sought to evaluate the cross-sectional and longitudinal associations of the frequency of sauna bathing with renal function measures and chronic kidney disease (CKD). Materials and Methods:Baseline self-reported sauna bathing habits were assessed in 2071 men aged 42-61 years with normal kidney function. Baseline estimated glomerular filtration rate (GFR) and serum levels of creatinine, potassium (K) and sodium (Na) were measured, with only 11-year measurements of K and Na 11 years in a random subset of participants due to logistical reasons. Study participants were followed up for CKD diagnosed using KDOQI guidelines, which were collected from the National Hospital Discharge Registry. The associations of frequency of sauna bathing with renal function measures were evaluated using regression analyses. Hazard ratios (HRs; 95% CIs) were estimated for CKD.Results: There were no significant changes in baseline levels of estimated GFR, creatinine and Na comparing 4-7 sauna sessions/week versus 1 sauna session/ week; there was a slight increase in K .05 mmoL/L (95% CI, .00, .10; p = .033).There were no significant changes in levels of serum K and Na at 11 years. After 25.7 years overall median follow-up, 188 CKD cases were recorded. Comparing 4-7 sauna sessions/week with 1 sauna session/week, there was no evidence of an association with CKD .84 (95% CI, .46-1.53; p = .56).

The multifaceted benefits of passive heat therapies for extending the healthspan: A comprehensive review with a focus on Finnish sauna

“…Finnish sauna - In 2,071 middle-aged and older men aged 42–61 years with normal kidney function who were recruited into the KIHD prospective study, cross-sectional and longitudinal analysis showed that frequent sauna bathing (4–7 sauna sessions per week) was not associated with impaired renal function (as measured using estimated glomerular filtration rate and serum levels of creatinine, potassium and sodium) or the future risk of chronic kidney disease [ 59 ] ( Figure 2 ). Although intensive sweating, induced by sauna with dry or wet heat, usually increases losses of water, urea, sodium, potassium, and chloride, a sauna bath session does not cause significant longer-term changes in serum electrolyte or creatinine levels.…”

“…Model 3: Model 2 plus estimated glomerular filtration rate. Reproduced from Kunutsor SK, et al [ 59 ]. …”