Sauna Bathing and Incident Hypertension: A Prospective Cohort Study.
Level 3 - non-randomized controlled study
Prospective cohort study
PubMed 28633297 · doi:10.1093/ajh/hpx102
What was done
In the Kuopio Ischemic Heart Disease prospective cohort study in Eastern Finland, researchers tracked 1,621 men aged 42 to 60 years without hypertension at baseline over a median follow-up of 24.7 years. Sauna bathing frequency was evaluated via self-reported baseline questionnaire into three groups: 1 session/week, 2 to 3 sessions/week, and 4 to 7 sessions/week. Incident hypertension was defined as a physician diagnosis, SBP >140 mm Hg, DBP >90 mm Hg, or initiation of antihypertensive medication. Cox regression models evaluated hazard ratios adjusting for baseline age, smoking, BMI, systolic blood pressure, glucose, creatinine, alcohol intake, heart rate, family history of hypertension, socioeconomic status, and cardiorespiratory fitness.
What was found
During follow-up, 251 incident cases (15.5%) of hypertension occurred. Compared to men having 1 sauna session per week: - 2 to 3 sessions per week: HR 0.76 (95% CI: 0.57-1.02) after basic adjustment; fully adjusted HR 0.83 (95% CI: 0.59-1.18). - 4 to 7 sessions per week: HR 0.54 (95% CI: 0.32-0.91) after basic adjustment; fully adjusted HR 0.53 (95% CI: 0.28-0.98).
Why it matters
This study provides long-term prospective evidence that frequent sauna bathing is independently associated with a reduced risk of developing hypertension, suggesting a potential mechanism for the cardiovascular benefits of heat exposure.
Limits
The study included only middle-aged Finnish men, limiting generalizability to women, other age groups, and different ethnicities. Sauna habits were assessed only at baseline by questionnaire, without accounting for changes over the ~25-year follow-up. Potential residual confounding by unmeasured lifestyle or diet factors remains possible in observational cohorts.
Cited by
- supports Sauna use 2 to 3 times per week is associated with a 24% lower risk of hypertension, and 4 to 7 times per week is associated with a 46% lower risk.