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

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.

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.

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.