Sauna Bathing and Incident Hypertension: A Prospective Cohort Study

Abstract

BACKGROUND Sauna bathing is associated with reduced cardiovascular risk, but the mechanisms underlying this beneficial effect are not entirely understood. We aimed to assess the relationship between sauna bathing and risk of incident hypertension. METHODS Frequency of sauna bathing was ascertained using questionnaires in the Kuopio Ischemic Heart Disease Study, a prospective cohort study conducted in Eastern Finland that comprised a population-based sample of 1,621 men aged 42 to 60 years without hypertension at baseline. The incidence of hypertension was defined as a physician diagnosis of hypertension, systolic blood pressure (SBP) >140 mm Hg, diastolic blood pressure >90 mm Hg, or use of antihypertensive medication. RESULTS During a median follow-up of 24.7 years, 251 incident cases (15.5%) were recorded. In Cox regression analysis adjusted for baseline age, smoking, body mass index, and SBP; compared to participants reporting 1 sauna session per week, the hazard ratio for incident hypertension in participants reporting 2 to 3 sessions and 4 to 7 sessions was 0.76 (95% confidence interval: 0.57-1.02) and 0.54 (0.32-0.91), respectively. The corresponding hazard ratios were similar after further adjustment for glucose, creatinine, alcohol consumption, heart rate, family history of hypertension, socioeconomic status, and cardiorespiratory fitness: 0.83 (95% confidence interval: 0.59-1.18) and 0.53 (0.28-0.98), respectively. CONCLUSIONS Regular sauna bathing is associated with reduced risk of hypertension, which may be a mechanism underlying the decreased cardiovascular risk associated with sauna use. Further epidemiological and experimental studies could help elucidate the effects of sauna bathing on cardiovascular function.