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

Sauna bathing in northern Sweden: results from the MONICA study 2022

Frequent sauna bathing has been associated with a reduced risk of cardiovascular disease and proposed as a mediator for improved health. Therefore, the aim was to describe and compare sauna bathers with non-sauna bathers in northern Sweden based on their demographics, health and life attitudes, and to describe sauna bathers' sauna habits. Questions on sauna bathing habits were included in the questionnaire for the participants in the Northern Sweden MONICA (multinational monitoring of trends and determinants in cardiovascular disease) study, conducted during spring of 2022, inviting adults 25-74 years living in the two northernmost counties of Sweden (Norr- and Västerbotten), randomly selected from the population register. Of the 1180 participants in MONICA 2022, 971 (82%) answered the question about sauna bathing. Of these, 641 (66%) were defined as sauna bathers. Sauna bathers reported less hypertension diagnosis and self-reported pain. They also reported higher levels of happiness and energy, more satisfying sleep patterns, as well as better general and mental health. Sauna bathers were younger, more often men and found to have a healthier life-profile compared to non-sauna bathers. Additionally, the results suggest that the positive effects associated with sauna bathing plateaued from 1-4 times per month.

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.

The Interplay of Type 2 Diabetes Status, Cardiorespiratory Fitness Level, and Sudden Cardiac Death: A Prospective Cohort Study

Background

To evaluate the individual and joint effects of type 2 diabetes (T2D) status and cardiorespiratory fitness (CRF) level with sudden cardiac death (SCD) risk.

Methods

Prevalent T2D was defined based on guideline recommendations, and CRF level was assessed using a respiratory gas-exchange analyzer during exercise testing at baseline, in 2308 men aged 42-61 years. T2D status was classified as either "Yes" or "No," and CRF level was classified as low, medium, or high. Cox regression analysis was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for SCD.

Results

A total of 264 SCDs occurred during a median follow-up of 28.1 years. Comparing Yes vs No history of T2D, the multivariable-adjusted HR (95% CI) for SCD was 1.79 (1.19-2.72). Comparing low vs high CRF levels, the corresponding adjusted HR (95% CI) for SCD was 1.77 (1.21-2.58). The HRs persisted when T2D status was further adjusted for CRF level, and vice versa. Compared with No-T2D & medium-high CRF level, men with No-T2D & low CRF and those with Yes-T2D & low CRF had an increased SCD risk: (HR = 1.87, 95% CI, 1.38-2.55) and (HR = 3.34, 95% CI, 2.00-5.57), respectively. No significant association occurred between men with Yes-T2D & medium-high CRF and SCD risk (HR = 1.46, 95% CI, 0.46-4.65). Modest evidence indicated the presence of additive and multiplicative interactions between T2D status and CRF level, in relation to SCD.

Conclusions

An interplay exists between T2D status, CRF level, and SCD risk in middle-aged and older men. Higher CRF levels may mitigate the increased SCD risk observed in men with T2D.

Enhancing Cardiorespiratory Fitness Through Sauna Bathing: Insights From the Kuopio Ischemic Heart Disease Prospective Study

PURPOSE

The physiological adaptations stimulated by a sauna bath (SB) are similar to those produced by moderate- or high-intensity physical activity (PA), but the relationship between SB and cardiorespiratory fitness (CRF) is not clear. The objective of this study was to evaluate the cross-sectional and longitudinal associations between frequency and duration of SB with CRF.

METHODS

Baseline SB habits were assessed in 2012 men aged 42 -61 yr. CRF was directly measured using a respiratory gas exchange analyzer during cardiopulmonary exercise testing at baseline and 11 yr later. The associations of SB frequency and duration with baseline and 11-yr levels of CRF were examined using robust regression analyses adjusted for several confounders, including lifestyle factors such as PA.

RESULTS

In baseline analysis, a unit increase in sauna sessions/wk was associated with an increase in CRF 0.30 mL/kg/min (standard error [SE]: 0.14; P = .034). Alternatively, compared with a single sauna sessions/wk, 2-3 and 4-7 sauna sessions/wk was each associated with significant increases in levels of CRF: 0.84 mL/kg/min (SE: 0.32; P = .008) and 1.17 mL/kg/min (SE: 0.57; P = .041), respectively. In longitudinal analysis, frequent SB was associated with increases in 11-yr CRF levels, but this was only significant for 2-3 sauna sessions/wk compared with a single sauna sessions/wk: 1.22 mL/kg/min (SE: 0.59; P = .038). Duration of SB was not significantly associated with CRF levels in cross-sectional and longitudinal analyses.

CONCLUSIONS

Frequent SB may improve levels of CRF independently of PA. These results warrant replication in robust definitive randomized controlled trials.

Frequent sauna bathing and psychosis: Interrelationship with cardiorespiratory fitness

Frequent sauna bathing and higher cardiorespiratory fitness (CRF) levels may play a role in reducing the risk of mental disorders such as psychosis, however, data on their joint contributions is scanty. We aimed to investigate the interplay between sauna bathing, CRF and psychosis risk using a population-based prospective study. Self-reported frequency of sauna bathing (FSB) and CRF measured by respiratory gas analyses were assessed at baseline in 2221 men aged 42-61 years who had no history of psychosis. Frequency of sauna bathing was categorized as low and high (≤2 and 3-7 sessions/week, respectively) and CRF as tertiles (low, medium and high). Hazard ratios (HRs) with 95% CIs were estimated. During a median follow-up of 25.2 years, 215 psychotic disorders were recorded. Comparing high vs low FSB, the multivariable-adjusted HRs (95% CIs) for psychosis was 0.49 (0.32-0.74), which persisted on further adjustment for CRF 0.50 (0.33-0.75). Compared to low CRF, the multivariable-adjusted HRs (95% CIs) for medium and high CRF levels were 0.65 (0.46-0.90) and 0.75 (0.52-1.07) respectively. Compared to low FSB & low CRF, the HRs (95% CIs) for low FSB & medium-high CRF, high FSB & low CRF, and high FSB & medium-high CRF were 0.62 (0.45-0.84), 0.26 (0.11-0.60), and 0.41 (0.25-0.68) respectively. Frequent sauna baths and medium-high CRF levels appear to each independently decrease psychosis risk. However, frequent sauna bathing may be related to a reduced risk of psychosis irrespective of fitness levels and might be a stronger risk indicator for psychosis than CRF.

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.

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.