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

Passive heat therapy is characterized by exposure to a high environmental temperature for a brief period. There are several types of passive heat therapy which include hot tubs, Waon therapy, hydrotherapy, sanarium, steam baths, infrared saunas and Finnish saunas. The most commonly used and widely studied till date are the Finnish saunas, which are characterized by high temperatures (ranging from 80-100°C) and dry air with relative humidity varying from 10-20%. The goal of this review is to provide a summary of the current evidence on the impact of passive heat therapies particularly Finnish saunas on various health outcomes, while acknowledging the potential of these therapies to contribute to the extension of healthspan, based on their demonstrated health benefits and disease prevention capabilities. The Finnish saunas have the most consistent and robust evidence regarding health benefits and they have been shown to decrease the risk of health outcomes such as hypertension, cardiovascular disease, thromboembolism, dementia, and respiratory conditions; may improve the severity of musculoskeletal disorders, COVID-19, headache and flu, while also improving mental well-being, sleep, and longevity. Finnish saunas may also augment the beneficial effects of other protective lifestyle factors such as physical activity. The beneficial effects of passive heat therapies may be linked to their anti-inflammatory, cytoprotective and anti-oxidant properties and synergistic effects on neuroendocrine, circulatory, cardiovascular and immune function. Passive heat therapies, notably Finnish saunas, are emerging as potentially powerful and holistic strategies to promoting health and extending the healthspan in all populations.

Sauna bathing and mortality risk: unraveling the interaction with systolic blood pressure in a cohort of Finnish men.

Objectives: This cohort study aimed to investigate the potential interplay between systolic blood pressure (SBP), frequency of sauna bathing (FSB), and all-cause mortality risk among Caucasian men. Design: A prospective study was conducted, involving 2575 men aged 42 to 61 years. Baseline assessments included resting blood pressure measurements and self-reported sauna bathing habits. SBP levels were categorized as normal (<140 mmHg) or high (≥140 mmHg), while FSB was classified as low (≤2 sessions/week) or high (3-7 sessions/week). Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using Cox regression analysis, while adjusting for lifestyle factors, lipids, inflammation, and comorbidities. Results: Over a median follow-up of 27.8 years, 1,618 deaths were recorded. In the adjusted analysis, individuals with high SBP versus low SBP showed a 29% increased all-cause mortality risk (HR 1.29, 95% CI 1.16-1.43). Similarly, those with low FSB versus high FSB exhibited a 16% elevated mortality risk (HR 1.16, 95% CI 1.02-1.31). When considering combined effects, participants with high SBP-low FSB had a 47% higher mortality risk (HR 1.47, 95% CI 1.24-1.74) compared to those with normal SBP-high FSB. However, no significant association was observed between individuals with high SBP-high FSB and mortality risk (HR 1.24, 95% CI 0.98-1.57). There were potential additive and multiplicative interactions between SBP and sauna bathing concerning mortality risk. Conclusions: This study reveals a potential interplay between SBP, sauna bathing, and mortality risk in Finnish men. Frequent sauna bathing may mitigate the increased mortality risk associated with elevated SBP.

Does the Combination of Finnish Sauna Bathing and Other Lifestyle Factors Confer Additional Health Benefits? A Review of the Evidence.

Sauna bathing, a tradition deeply rooted in the Finnish culture, has been used for thousands of years for leisure, relaxation, and wellness. Sauna bathing is linked with substantial health benefits beyond its use for leisure and relaxation. Several observational and interventional studies suggest that regular or frequent sauna bathing reduces the incidence of vascular and nonvascular diseases, such as hypertension, cardiovascular disease, dementia, and respiratory conditions; may improve the severity of conditions such as musculoskeletal disorders, COVID-19, headache, and influenza; and increases the life span. The beneficial effects of sauna bathing on adverse outcomes have been linked to its blood pressure-reducing, anti-inflammatory, antioxidant, cytoprotective, and stress-reducing properties and its synergistic effect on neuroendocrine, circulatory, cardiovascular, and immune function. Evidence suggests that frequent sauna bathing is an emerging protective risk factor that may augment the beneficial effects of other protective risk or lifestyle factors, such as physical activity and cardiorespiratory fitness, or attenuate or offset the adverse effects of other risk factors, such as high blood pressure, systemic inflammation, and low socioeconomic status. This review summarizes the available epidemiologic and interventional evidence linking the combined effects of Finnish sauna bathing and other risk factors on vascular outcomes including cardiovascular disease and intermediate cardiovascular phenotypes, nonvascular outcomes, and mortality. We also discuss the mechanistic pathways underlying the joint contributions of Finnish sauna bathing and other risk factors on health outcomes, the public health and clinical implications of the findings, gaps in the existing evidence base, and future directions.

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

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). CONCLUSIONS: Cross-sectional and longitudinal observational evidence suggests that frequent sauna bathing is not associated with impaired renal function or the future risk of CKD.

Inflammation, sauna bathing, and all-cause mortality in middle-aged and older Finnish men: a cohort study.

Inflammation and sauna bathing are each related to the risk of all-cause mortality. The interplay between inflammation, sauna bathing and all-cause mortality is not well understood. We aimed to evaluate the separate and joint associations of inflammation (high sensitivity C-reactive protein, hsCRP) and frequency of sauna bathing (FSB) with all-cause mortality in a cohort of Caucasian men. We used the Kuopio Ischaemic Heart Disease Study cohort comprising 2575 men aged 42-61 years at baseline. Serum hsCRP was measured using an immunometric assay and sauna bathing habits were assessed by a self-administered questionnaire. High sensitivity CRP was categorized as normal and high (≤ 3 and > 3 mg/L, respectively) and FSB as low and high (defined as ≤ 2 and 3-7 sessions/week respectively). A total of 1618 deaths occurred during a median follow-up of 27.8 years. Comparing high vs normal hsCRP levels, the multivariable-adjusted HR (95% CI) for all-cause mortality was 1.27 (1.13-1.44). Comparing high vs low FSB, the multivariable-adjusted HR (95% CI) for all-cause mortality was 0.86 (0.76-0.97). Compared with normal hsCRP-low FSB, high hsCRP-low FSB was associated with an increased risk of all-cause mortality 1.28 (1.12-1.47), with no evidence of an association for high hsCRP-high FSB and all-cause mortality risk 1.06 (0.81-1.40). Positive additive and multiplicative interactions were found between hsCRP and FSB in relation to mortality. In a general Finnish male population, both hsCRP and FSB are each independently associated with all-cause mortality. However, frequent sauna baths appear to offset the increased all-cause mortality risk related to high hsCRP levels.

Frequent sauna bathing offsets the increased risk of death due to low socioeconomic status: A prospective cohort study of middle-aged and older men.

BACKGROUND AND AIM: Low socioeconomic status (SES) and frequent sauna bathing are associated with increased and decreased risk of all-cause mortality, respectively. Whether there is an interplay among SES, sauna bathing and all-cause mortality risk is not known. We aimed to evaluate the separate and joint associations of SES and frequency of sauna bathing (FSB) with all-cause mortality risk in a prospective cohort study. METHODS: We employed the Kuopio Ischaemic Heart Disease Study cohort comprising of 2575 men aged 42-61 years at study entry. Self-reported SES and sauna bathing habits were assessed at baseline. Socioeconomic status was categorized as low and high (median cutoff) and FSB as low and high (defined as ≤2 and 3-7 sessions/week, respectively). RESULTS: During a median follow-up of 27.8 years, 1618 deaths occurred. Comparing low vs high SES, the multivariable-adjusted HR (95 % CI) for all-cause mortality was 1.31 (1.18-1.45). Comparing high vs low FSB, the multivariable-adjusted HR (95 % CI) for all-cause mortality was 0.86 (0.76-0.97). Compared with high SES-low FSB, low SES-low FSB was associated with an increased risk of all-cause mortality 1.35 (1.20-1.51), without significant evidence of an association for low SES-high FSB and all-cause mortality risk 1.07 (0.89-1.29). Positive additive and multiplicative interactions were found between SES and FSB. CONCLUSIONS: There exists an interplay among SES, sauna bathing and all-cause mortality risk in a general Finnish male population. Frequent sauna baths may offset the increased overall mortality risk due to low SES.

Effects of regular sauna bathing in conjunction with exercise on cardiovascular function: a multi-arm, randomized controlled trial.

Regular exercise and sauna bathing have each been shown to improve cardiovascular function in clinical populations. However, experimental data on the cardiovascular adaptations to regular exercise in conjunction with sauna bathing in the general population are lacking. Therefore, we compared the effects of exercise and sauna bathing to regular exercise using a multi-arm randomized controlled trial. Participants (n = 47) aged 49 ± 9 with low physical activity levels and at least one traditional cardiovascular disease (CVD) risk factor were randomly assigned (1:1:1) to guideline-based regular exercise and 15-min postexercise sauna (EXS), guideline-based regular exercise (EXE), or control (CON) for 8 wk. The primary outcomes were blood pressure (BP) and cardiorespiratory fitness (CRF). Secondary outcomes included fat mass, total cholesterol levels, and arterial stiffness. EXE had a greater change in CRF (+6.2 mL/kg/min; 95% CI, +4.2 to +8.3 mL/kg/min) and fat mass but no differences in BP when compared with CON. EXS displayed greater change in CRF (+2.7 mL/kg/min; 95% CI, +0.2 to +5.3 mL/kg/min), lower systolic BP (-8.0 mmHg; 95% CI, -14.6 to -1.4 mmHg), and lower total cholesterol levels compared with EXE. Regular exercise improved CRF and body composition in sedentary adults with CVD risk factors. However, when combined with exercise, sauna bathing demonstrated a substantially supplementary effect on CRF, systolic BP, and total cholesterol levels. Sauna bathing is a valuable lifestyle tool that complements exercise for improving CRF and decreasing systolic BP. Future research should focus on the duration and frequency of exposure to ascertain the dose-response relationship.

Attenuated Risk of Pneumonia Due to Inflammation by Frequent Sauna Baths: A PROSPECTIVE COHORT STUDY.

PURPOSE: Inflammatory pathways are involved in the pathogenesis of pneumonia. Frequent sauna sessions may reduce the risk of respiratory tract infections including pneumonia independent of inflammation. We aimed to evaluate the independent and joint associations of high-sensitivity C-reactive protein (hsCRP) and frequency of sauna bathing (FSB) with risk of pneumonia in a prospective cohort study. METHODS: Serum hsCRP as an inflammatory marker was measured using an immunometric assay and FSB was assessed by self-reported sauna bathing habits at baseline in 2264 men aged 42-61 yr. Serum hsCRP was categorized as normal and high (≤3 and >3 mg/L, respectively) and FSB as low and high (defined as ≤1 and 2-7 sessions/wk, respectively). Multivariable-adjusted HRs (CIs) were calculated for incident pneumonia. RESULTS: A total of 528 cases of pneumonia occurred during a median follow-up of 26.6 yr. Comparing high versus normal hsCRP, the multivariable-adjusted risk for pneumonia was HR = 1.30 (95% CI, 1.04-1.62). The corresponding risk was HR = 0.79 (95% CI, 0.66-0.95) comparing high versus low FSB. Compared with men with normal hsCRP and low FSB, high hsCRP and low FSB was associated with an increased risk of pneumonia in multivariable analysis (HR = 1.67: 95% CI, 1.21-2.29), with no evidence of an association for high hsCRP and high FSB and pneumonia (HR = 0.94: 95% CI, 0.69-1.29). CONCLUSIONS: In a general middle-aged to older male Caucasian population, frequent sauna baths attenuated the increased risk of pneumonia due to inflammation.

High fitness levels, frequent sauna bathing and risk of pneumonia in a cohort study: Are there potential implications for COVID-19?

BACKGROUND: There is an ongoing debate on a potential protective role of habitual physical activity and passive heat therapy on the risk of COVID-19, a respiratory infectious disease that can manifest as severe pneumonia. To explore these putative roles, we evaluated the independent and joint associations of cardiorespiratory fitness (CRF) and frequency of sauna bathing (FSB) with pneumonia risk in a prospective cohort study of 2275 men aged 42-61 years at recruitment. MATERIAL AND METHODS: Objectively measured CRF and self-reported sauna bathing habits were assessed at baseline. CRF was categorized as low and high (median cut-offs) and FSB as low and high (defined as ≤1 and 2-7 sessions/wk, respectively). Multivariable-adjusted hazard ratios (HRs) with confidence intervals (CIs) were calculated for incident pneumonia. RESULTS: During a median follow-up of 26.6 years, 529 cases of pneumonia occurred. Comparing high vs low CRF, the multivariable-adjusted HR (95% CIs) for pneumonia was 0.75 (0.61-0.91). Comparing high vs low FSB, the corresponding HR was 0.81 (0.68-0.97). Compared to men with low CRF & low FSB, the multivariable-adjusted HRs of pneumonia for the following groups: high CRF & low FSB; low CRF & high FSB; and high CRF & high FSB were 0.88 (0.65-1.20), 0.89 (0.71-1.13), and 0.62 (0.48-0.80) respectively. CONCLUSIONS: In a general male Caucasian population, a combination of high fitness levels and frequent sauna baths is associated with a substantially lowered future pneumonia risk compared with each modality alone. The implications of these findings in altering COVID-19 disease or its severity deserve study.

Effect of Omega-3 Dosage on Cardiovascular Outcomes: An Updated Meta-Analysis and Meta-Regression of Interventional Trials.

OBJECTIVES: To quantify the effect of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids on cardiovascular disease (CVD) prevention and the effect of dosage. METHODS: This study is designed as a random effects meta-analysis and meta-regression of randomized control trials with EPA/DHA supplementation. This is an update and expanded analysis of a previously published meta-analysis which covers all randomized control trials with EPA/DHA interventions and cardiovascular outcomes published before August 2019. The outcomes included are myocardial infarction (MI), coronary heart disease (CHD) events, CVD events (a composite of MI, angina, stroke, heart failure, peripheral arterial disease, sudden death, and non-scheduled cardiovascular surgical interventions), CHD mortality and fatal MI. The strength of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation framework. RESULTS: A total of 40 studies with a combined 135,267 participants were included. Supplementation was associated with reduced risk of MI (relative risk [RR], 0.87; 95% CI, 0.80 to 0.96), high certainty number needed to treat (NNT) of 272; CHD events (RR, 0.90; 95% CI, 0.84 to 0.97), high certainty NNT of 192; fatal MI (RR, 0.65; 95% CI, 0.46 to 0.91]), moderate certainty NNT = 128; and CHD mortality (RR, 0.91; 95% CI, 0.85 to 0.98), low certainty NNT = 431, but not CVD events (RR, 0.95; 95% CI, 0.90 to 1.00). The effect is dose dependent for CVD events and MI. CONCLUSION: Cardiovascular disease remains the leading cause of death worldwide. Supplementation with EPA and DHA is an effective lifestyle strategy for CVD prevention, and the protective effect probably increases with dosage.

Sauna bathing frequency in Finland and the impact of COVID-19.

OBJECTIVES: Recent research has revealed multiple potential health benefits of frequent sauna bathing. Finland is a country with extraordinary sauna culture and bathing opportunities. However, coronavirus disease 2019 (COVID-19) pandemic introduced regulations and unprecedented closures to shared sauna facilities. In this study we aimed to examine the previously unknown baseline bathing frequency and its possible change during the epidemic. DESIGN: We investigated several aspects of sauna bathing with self-reports: the frequency, its possible changes, reasons for change, and beliefs about its health effects among a representative sample of thousand Finns aged 18-75 years. This online survey was administered in May 2020. RESULTS: Before the pandemic, 59 % of our respondents had enjoyed sauna at least once a week. Since the pandemic began, up to 23 % had reduced or stopped their bathing. This was often due to restricted sauna access. However, 11 % of respondents bathed more frequently and attributed this change to seeking relaxation and passing time. These findings demonstrate a surprising flexibility in this health-promoting national pastime. Men were more active bathers than women overall and women under 35 enjoy sauna more seldom than older women. Only 7.9 % of all respondents bathed at least four times a week, exceeding a suggested threshold for maximum health benefits. CONCLUSIONS: Finnish people are active sauna bathers. The COVID-19 pandemic demonstrated that the frequency of bathing is dependent on good access to sauna facilities. This flexibility and wide access could be exploited to improve public health in the long term if more frequent bathing became a standard.

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 reduces the risk of venous thromboembolism: a prospective cohort study.

Emerging evidence suggests there is an inverse and independent association between sauna bathing and arterial thrombotic disease. However, the potential association between sauna bathing and venous thromboembolism (VTE) has not yet been investigated. We aimed to assess the prospective association between frequency of sauna bathing and the risk of VTE. Baseline sauna bathing habits were assessed in 2242 men aged 42-61 years without a history of VTE in the Kuopio Ischemic Heart Disease prospective cohort. Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for VTE. During a median follow-up of 24.9 years, 146 (6.5%) incident VTE events were recorded. In age-adjusted analyses, the HRs 95% (CIs) of VTE were 0.67 (0.47-0.96) and 0.95 (0.53-1.70) for participants who had 2-3 and ≥ 4 sauna sessions per week respectively compared with participants who had ≤ 1 sauna session per week. After further adjustment for several established risk factors including lifestyle factors, the corresponding HRs (95% CIs) were 0.67 (0.46-0.96) and 0.92 (0.51-1.68) respectively. Having sauna baths was associated with a reduced risk of VTE in a middle-aged male Caucasian population. Further studies in other populations and age groups are required to confirm these findings.