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

Unraveling the link between cardiorespiratory fitness and cancer: a state-of-the-art review

Cardiorespiratory fitness (CRF) not only reflects an individual's capacity to perform physical activities but also encapsulates broader effects on the basic biology of aging. This review aims to summarize the evidence on the influence of CRF on overall and site-specific cancer risks. It delves into the biological mechanisms through which CRF may exert its effects, explores the clinical implications of these findings, identifies gaps in the current evidence base, and suggests directions for future research. The synthesis of findings reveals that higher CRF levels (general threshold of > 7 METs) are consistently associated with a reduced risk of a range of cancers, including head and neck, lung, breast, gastrointestinal, particularly pancreatic and colorectal, bladder, overall cancer incidence and mortality, and potentially stomach and liver, bile duct, and gall bladder cancers. These inverse associations between CRF and cancer risk do not generally differ across age groups, sex, race, or adiposity, suggesting a universal protective effect of CRF. Nonetheless, evidence linking CRF with skin, mouth and pharynx, kidney, and endometrial cancers is limited and inconclusive. Conversely, higher CRF levels may be potentially linked to an increased risk of prostate cancer and hematological malignancies, such as leukemia and myeloma, although the evidence is still not conclusive. CRF appears to play a significant role in reducing the risk of several cancers through various biological mechanisms, including inflammation reduction, immune system enhancement, hormonal regulation, and metabolic improvements. Overall, enhancing CRF through regular physical activity offers a vital, accessible strategy for reducing cancer risk and extending the health span. Future research should aim to fill the existing evidence gaps regarding specific cancers and elucidate the detailed dose-response relationships between CRF levels and cancer risk. Studies are also needed to elucidate the causal relationships and mechanistic pathways linking CRF to cancer outcomes.

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.

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.

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.

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.

The Interplay between Systolic Blood Pressure, Sauna Bathing, and Cardiovascular Mortality in Middle-Aged and Older Finnish Men: A Cohort Study

OBJECTIVES

Elevated systolic blood pressure (SBP) is associated with an increased risk of cardiovascular disease (CVD) mortality, whereas frequent sauna bathing reduces the risk. Whether frequent sauna bathing mitigates CVD mortality among adults with elevated SBP has not been previously investigated.

DESIGN AND SETTING

We examined the interactions between SBP and frequency of sauna bathing (FSB) with the risk of CVD mortality in a cohort of Caucasian men.

PARTICIPANTS

The Kuopio Ischaemic Heart Disease Study cohort comprising of 2,575 men aged 42-61 years at baseline was employed for this prospective study analysis.

MEASUREMENTS

Resting blood pressure was measured using a standardized protocol and sauna bathing habits were assessed by a self-administered questionnaire. Systolic blood pressure was categorized as normal and high (<140 and ≥140 mmHg, respectively) and FSB as low and high (defined as ≤ 2 and 3-7 sessions/week, respectively).

RESULTS

A total of 744 CVD deaths were recorded during a median follow-up of 27.8 yr. Comparing high vs normal SBP, the multivariable-adjusted HR (95% CI) for CVD mortality was 1.44 (1.23-1.68). Comparing low vs high FSB, the multivariable-adjusted HR (95% CI) for CVD mortality was 1.24 (1.03-1.51). The associations persisted following mutual adjustment for each exposure. Compared with men with normal SBP-high FSB, high SBP-low FSB was associated with an increased risk of CVD mortality 1.81 (1.39-2.36), with attenuated but persisting evidence of an association for men with high SBP and high FSB 1.52 (1.06-2.16). When SBP was categorized as normal and high (<130 and ≥130 mmHg, respectively), there was no evidence of an association for men with high SBP and high FSB 1.11 (0.77-1.61).

CONCLUSION

There might be an interaction between SBP, sauna bathing and CVD mortality risk in middle-aged and older Caucasian males. Frequent sauna baths may offset the increased risk of CVD mortality in men with high-normal SBP but not elevated SBP.

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.

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.

COVID-19 Infection Alters the Microbiome: Elite Athletes and Sedentary Patients Have Similar Bacterial Flora

Regular exercise can upgrade the efficiency of the immune system and beneficially alter the composition of the gastro-intestinal microbiome. We tested the hypothesis that active athletes have a more diverse microbiome than sedentary subjects, which could provide better protection against COVID-19 during infection. Twenty active competing athletes (CA) (16 male and 4 females of the national first and second leagues), aged 24.15 ± 4.7 years, and 20 sedentary subjects (SED) (15 male and 5 females), aged 27.75 ± 7.5 years, who had been diagnosed as positive for COVID-19 by a PCR test, served as subjects for the study. Fecal samples collected five to eight days after diagnosis and three weeks after a negative COVID-19 PCR test were used for microbiome analysis. Except for two individuals, all subjects reported very mild and/or mild symptoms of COVID-19 and stayed at home under quarantine. Significant differences were not found in the bacterial flora of trained and untrained subjects. On the other hand, during COVID-19 infection, at the phylum level, the relative abundance of Bacteroidetes was elevated during COVID-19 compared to the level measured three weeks after a negative PCR test (p < 0.05) when all subjects were included in the statistical analysis. Since it is known that Bacteroidetes can suppress toll-like receptor 4 and ACE2-dependent signaling, thus enhancing resistance against pro-inflammatory cytokines, it is suggested that Bacteroidetes provide protection against severe COVID-19 infection. There is no difference in the microbiome bacterial flora of trained and untrained subjects during and after a mild level of COVID-19 infection.

Covid-19 and the next outbreak: decreasing frailty by using mild stress?

The coronavirus disease 2019 (Covid-19) has resulted in many deaths, particularly of very old or obese people. These people are at risk to die in the event of an outbreak, like under one-year old babies were at risk to die one century ago from various diseases. It is argued that mild stress could help people to resist new outbreaks. The people who are obese because of bad feeding habits (snacking, junk food, overfeeding) and inactivity should adopt more healthy behaviours. Because an inactive way of life at old age can increase frailty, physical and mental activities should be kept at the highest possible level in elderly people, particularly if they live in retirement homes. In the event of an outbreak, management staff of these homes should not confine residents in their room for weeks or months, as it can increase inactivity, under-nutrition, sarcopenia, and depressive symptoms. People with or without co-morbidities should be active and one could wonder whether other mild stresses such as sauna bathing could help to better resist infection.

A Possible Preventive Role of Physically Active Lifestyle during the SARS-CoV-2 Pandemic; Might Regular Cold-Water Swimming and Exercise Reduce the Symptom Severity of COVID-19?

The objective of this study was to investigate the incidence and course of COVID-19 and the risk of an upper respiratory tract infection in a group of people with physically active lifestyles. Data were collected anonymously using an online survey platform during December 2020. The age of participants ranged from 18 to 65 years. Out of 2343 participants, 11.5% overcame COVID-19 infection. Relative to the control group (CTRL), physically active, cold-water swimmers (PACW) did not exhibit a lower risk of incidence for COVID-19 (RR 1.074, CI 95% (0.710–1.625). However, PACW had a higher chance of having an asymptomatic course of COVID-19 (RR 2.321, CI 95% (0.836–6.442); p < 0.05) and a higher chance of only having an acute respiratory infection once or less per year than CTRL (RR 1.923, CI 95% (1.1641–2.253); p < 0.01). Furthermore, PACW exhibited a lower incidence of acute respiratory infection occurring more than twice per year (RR 0.258, CI 95% (0.138–0.483); p < 0.01). Cold-water swimming and physical activity may not lessen the risk of COVID-19 in recreational athletes. However, a physically active lifestyle might have a positive effect on the rate of incidence of acute respiratory infection and on the severity of COVID-19 symptoms.

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.