The view of aging as a non-modifiable inevitability has given way to the possibilities of extending lifespan and promoting healthspan. Healthspan is defined as the period of one’s life spent in good health, free from the chronic diseases and disabilities that commonly accompany aging(1).
The extension of healthspan compresses the time spent in ill health, shifting it one’s later years.
Sauna use has emerged as a credible means to enhance lifespan and extend healthspan.
Bathing oneself in heat for purposes of purification, cleansing, and healing is an ancient practice, observed for thousands of years across many cultures. Sauna use, also known as “sauna bathing”, is characterized by short-term passive exposure to high temperatures, typically ranging from 113 °F to 212 °F.
This exposure elicits mild hyperthermia, increasing the body’s core temperature which causes a thermoregulatory response that involves neuroendocrine, cardiovascular, and cytoprotective mechanisms(2).
Compelling data from observational, interventional, and mechanistic studies support the claims that sauna use extends healthspan.
Physiological Response to Heat Stress
Exposure to high temperatures stresses the body, eliciting a rapid, robust response that primarily affects the skin and cardiovascular systems.
Cardiac output may increase by as much as 60-70% while the heart rate increases and stroke volume remains stable(3).
Concurrently, about 50-70% of the body’s circulation redistributes from the core to the skin to facilitate sweating, driving fluid losses at a rate of approximately 0.6 to 1.0 kg per hour.
Plasma volume also increases which provides a reserve source of fluid for sweating, cools the body to prevent rapid increases in core body temperature, and promotes heat tolerance.
Figure: Physiological response to heat stress. Heat stress increases core body temperature, promotes blood redistribution, and increases sweat production. Heart rate and cardiac output increase, while stroke volume remains stable.
Repeated sauna use acclimates the body to heat and optimizes the body’s response to future exposures.
Protective mechanisms occur that not only repair cell damage but also provide protection for subsequent exposures to more overwhelming stressors.
Many of the physiological responses to sauna use are remarkably similar to those experienced during moderate to vigorous intensity aerobic exercise, and sauna use has been indicated as an alternative to aerobic exercise for people who are unable to engage in
physical activity due to chronic disease or physical limitations(4).
There are numerous molecular mechanisms that mitigate protein damage and aggregation and activate endogenous antioxidant, repair, and degradation processes.
One of the main molecular mechanisms is increased expression of heat shock proteins.
Increased expression of heat shock proteins prevents protein disorder and aggregation by repairing proteins that have been damaged, and animal evidence suggests that heat shock proteins may offer
protection against neurodegenerative diseases(5).
In addition, heat shock proteins also moderate muscle atrophy and are associated with human longevity.
Figure: Heat shock proteins provide protection against cellular stress. Heat stress promotes increased expression of heat shock proteins (HSPs), which prevent protein disorder and aggregation by repairing proteins that have been damaged, providing protection against chronic diseases. Increased expression of HSPs also slows muscle atrophy and promotes longevity.
Influences of Sauna Bathing on Extending Healthspan
Below I will summarize and provide key benefits on how sauna bathing promotes and extends healthspan.
Promotion of cardiovascular health.
Heat exposure produces protective responses that promote cardiovascular health. Some of these responses reiterate those experienced during exercise (e.g., increase heart rate and blood pressure).
Like exercise, regular sauna use generally decreases systolic and diastolic blood pressure; increases left ventricular ejection fraction and reduces left ventricular ejection time, enhances arterial compliance, and improves flow mediated dilation, a measure of endothelial function(6).
Figure: Long-term sauna use protects against cardiovascular disease. Long-term sauna use induces protective responses against the pathological processes that drive cardiovascular disease and related disability by decreasing resting systolic and diastolic blood pressure; increasing left ventricular ejection fraction and reducing left ventricular ejection time; enhancing arterial compliance; and improving flow-mediated dilation, a measure of endothelial function.
Cardiovascular disease-related mortality
Evidence indicates dose-dependent cardiovascular benefits associated with the frequency and duration of sauna use. Whereas risk for sudden cardiac death was 22% lower for men using the sauna 2-3 times per week, the risk was 63% lower for men who used the sauna 4-7 times per week, compared to men who used the sauna once per week.
Risk for fatal cardiovascular disease was 27% lower for men utilizing the sauna 2-3 times a week and 50% lower for men using the sauna 4-7 times a week, compared to men who used the sauna once per week.
Similarly, duration plays an effect with longer durations being more beneficial.
For example, the risk for sudden cardiac death among men was 7% lower among those whose sauna sessions were 11 min or less and was 52% lower among those whose sauna session were 19 min or more. Additionally, aerobic exercise in combination with frequent sauna use has a synergistic effect on lowering cardiovascular-related mortality and all-cause mortality.
Congestive heart failure
Evidence from controlled clinical trials demonstrated that sauna therapy improved patients B-type natriuretic peptide levels (a biomarker of congestive heart failure), endurance, cardiothoracic ratio, and disease status compared to those who received standard medical care(5). A control group that received conventional medical therapy showed no significant changes.
Ischemic heart disease
The effects of sauna in patients with ischemic heart disease with chronic total coronary artery occlusion demonstrated improved vascular endothelial function as measured by flow-mediated dilation of the brachial artery. No significant improvements were observed in the control group that received standard medical care.
Peripheral artery disease
Sauna use over a period of 10 weeks demonstrated improvements in pain levels, walking endurance, and lower extremity blood flow.
Dyslipidemia
Regular sauna exposure modulated serum cholesterol and lipoproteins in healthy adults. Evidence shows sauna use reduced both total plasma cholesterol and low-density lipoprotein concentration.
Hypertension
A common element among sauna users is lower incidence of hypertension through improvements in arterial compliance. Interestingly, a single sauna session has been shown to lower blood pressure and improve arterial compliance. Sauna use may serve as a non-pharmacological means to address, and potential prevent hypertension.
Endothelial dysfunction
Sauna therapy in patients with congestive heart failure enhanced endothelial function, as evidenced by significant increases in flow-mediated dilation; and improved cardiac function(7).
Left ventricular dysfunction
Both single-session and long-term sauna use enhanced left ventricular function in patients with congestive heart failure via reduced afterload associated with thermal vasodilation. Consequently, sauna use may have therapeutic value for treating late-stage cardiovascular disease(8).
Heart rate variability
A higher heart rate (HRV) variability, or greater variability between heartbeats, is an indicator of autonomic nervous system health, making HRV a well-established marker of cardiovascular risk. Evidence indicates that sauna use elicits similar effects to exercise to increase HRV via modulation of the autonomic nervous system. Sauna use is a potential therapeutic strategy in the treatment of cardiac arrhythmias, which is a common feature of coronary heart failure.
Inflammation
Markers of inflammation increase with aging. Exercise incites an inflammatory response driven by the release of the pro-inflammatory cytokine IL-6, which in turn causes a counter response driven via the release of anti-inflammatory cytokines IL-1ra and IL-10(9).
This exercise-induced response is partly due to the increase in core body temperature that accompanies exertion and likely explains some of the benefits associated with regular exercise.
Passive strategies like sauna therapy that induce increases in body temperature may similarly reduce inflammation and may be particularly beneficial for individuals unable to engage in regular exercise due to physical or cognitive limitations(6).
C-reactive protein (CRP), an acute phase reactant, is an important inflammatory maker. CRP is associated with the development of atherosclerosis, loss of arterial compliance, and greater incidence of cardiovascular events(10).
Evidence indicates that sauna use decreases blood
(11).
Cognitive and Mental Health
Heat stress and exercise enhance the expression of brain-derived neurotrophic factor (BDNF), a protein that acts on neurons in the central and peripheral nervous systems to promote growth of new neurons. BDNF is also active in the hippocampus, cortex, cerebellum, and basal forebrain areas involved in learning, long term memory, and executive function.
Additionally, BDNF is produced in exercising muscle tissue, where it plays a role in muscle repair and growth of new muscle cells(12).
Research indicates whole-body hyperthermia increases serum BDNF levels and decreases plasma cortisol levels, which is another benefit from regular sauna therapy.
Neurodegenerative Diseases
Men that used the sauna 4-7 times a week had a 65% reduced risk of developing Alzheimer’s disease, compared to men who only used the sauna once per week(13).
Multiple mechanisms may be responsible for why frequent sauna use may mitigate neurodegenerative diseases. Blood flow is crucial to normal cognitive function. This is why cardiovascular diseases and cognitive decline are common comorbidities. Heat exposure enhances the production of BDNF to promote neurogenesis which is one of the reasons why sauna use plays a critical role in preventing Alzheimer’s disease(14).
Depression
Sauna use has been shown to reduce symptoms of depression. Some of these benefits on mood are due to the acute increase in plasma levels of pro-inflammatory IL-6 and anti-inflammatory IL-10, like effects observed following exercise(9).
Beta-endorphins and the opioid system
Beta-endorphins are endogenous opioids that are produced and stored primarily in the anterior pituitary gland of the brain. They play important roles in pain management and reward circuitry. Evidence suggests that beta-endorphins are responsible in part for the euphoric or pleasant sensations that commonly occur in response to exercise(15).
Sauna use stimulates robust increases in beta-endorphins.
Immune Function and Respiratory Infection
The degradation of immune function is one of the prominent features of aging. Evidence suggests that HSPs play critical roles in preserving immunological resilience. Sauna use is associated with reduced risk of developing certain chronic or acute respiratory illnesses, including pneumonia(16).
Evidence suggests that sauna therapy elicits improvements in respiratory function in men with obstructive pulmonary disease(17).
Additionally, sauna use is effective in reducing the incidence of common colds. The positive effects of sauna use on respiratory health may be related to decreases in oxidative stress and inflammation associated with hyperthermia or via direct effects on lung tissue.
Sauna use is associated with numerous health benefits, from cardiovascular and cognitive health to physical fitness. It is generally considered safe for healthy adults and may be safe for special populations with appropriate medical supervision.
Heat stress via sauna use produces molecular responses that protect the body from damage, like those produced by moderate- to
high-intensity training, and may offer a method to forestall the effects of aging and extend healthspan.
Now that you know how incredible sauna can be for your health, you can learn all about the benefits of cold water immersion
here.
References:
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