Finnish sauna bathing does not increase or decrease the risk of cancer in men: A prospective cohort study.

INTRODUCTION: Evidence suggests that heat therapy can be used to prevent and treat cancer; anecdotal reports suggest passive heat therapies may increase cancer risk. Finnish sauna bathing has been linked to a reduced risk of chronic diseases, but its association with cancer risk is unknown. We aimed to assess the prospective association between frequency of sauna bathing and the risk of all-cause and site-specific cancers using the Kuopio Ischemic Heart Disease prospective cohort. METHODS: Baseline sauna bathing habits were assessed in 2173 men aged 42-61 years with no history of cancer. Hazard ratios (HRs) with 95% confidence intervals (CIs) for cancer were calculated using Cox proportional hazard models. We corrected for within-person variability in sauna bathing habits using data from repeat assessments taken 11 years apart. RESULTS: During a median follow-up of 24.3 years, 588 (27.1%) all-cause cancer cases were recorded. The age-adjusted regression dilution ratio of sauna bathing frequency was 0.69 (0.62-0.76). In multivariable-adjusted analyses, the HRs (95% CIs) of all-cause cancer were 0.92 (0.76-1.11) and 0.92 (0.66-1.27) for men who had 2-3 and ≥4 sauna sessions per week, respectively, compared with men who had ≤1 sauna session per week. The non-significant findings were consistent for prostate, gastrointestinal and lung cancers on multivariate adjustment. CONCLUSION: Frequent Finnish sauna bathing is not associated with the risk of cancer in a middle-aged male Caucasian population. Further studies are required to confirm or refute these findings, particularly in women and other age groups.

Sauna bathing and systemic inflammation.

We aimed to investigate whether frequency of sauna bathing is associated with the levels of serum C-reactive protein. C-reactive protein is a leading blood marker of systemic inflammation. The study consisted of 2084 men (42-60 years) without acute or chronic inflammation. A total of 533 (25.6%), 1368 (65.6%), and 183 (8.8%) participants reported having a sauna bath once a week, 2-3 times, and 4-7 times per week; mean serum C-reactive protein levels were 2.41 (standard deviation 2.91), 2.00 (2.41), 1.65 (1.63) mmol/L, respectively. In a multivariable analysis adjusted for baseline age, body mass index, systolic blood pressure, smoking, type 2 diabetes, previous myocardial infarction, and serum low density lipoprotein cholesterol, alcohol consumption and physical activity, there was a significant inverse association between the frequency of sauna bathing and the level of C-reactive protein. Further studies are warranted to investigate the relationship between sauna bathing and systemic inflammation.

Sauna Bathing and Incident Hypertension: A Prospective Cohort Study.

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.

Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men.

Background: there are no previous studies linking repeated heat exposure of sauna and the risk of memory diseases. We aimed to investigate whether frequency of sauna bathing is associated with risk of dementia and Alzheimer's disease. Setting: prospective population-based study. Methods: the frequency of sauna bathing was assessed at baseline in the Kuopio Ischaemic Heart Disease population-based prospective cohort study of 2,315 apparently healthy men aged 42-60 years at baseline, with baseline examinations conducted between 1984 and 1989. Hazard ratios (HRs) with 95% confidence intervals (CIs) for dementia and Alzheimer's disease were ascertained using Cox-regression modelling with adjustment for potential confounders. Results: during a median follow-up of 20.7 (interquartile range 18.1-22.6) years, a total of 204 and 123 diagnosed cases of dementia and Alzheimer's disease were respectively recorded. In analysis adjusted for age, alcohol consumption, body mass index, systolic blood pressure, smoking status, Type 2 diabetes, previous myocardial infarction, resting heart rate and serum low-density lipoprotein cholesterol, compared with men with only 1 sauna bathing session per week, the HR for dementia was 0.78 (95% CI: 0.57-1.06) for 2-3 sauna bathing sessions per week and 0.34 (95% CI: 0.16-0.71) for 4-7 sauna bathing sessions per week. The corresponding HRs for Alzheimer's disease were 0.80 (95% CI: 0.53-1.20) and 0.35 (95% CI: 0.14-0.90). Conclusion: in this male population, moderate to high frequency of sauna bathing was associated with lowered risks of dementia and Alzheimer's disease. Further studies are warranted to establish the potential mechanisms linking sauna bathing and memory diseases.