Instalab ResearchBefore diving into long-term effects, it helps to understand what happens in the moment. A sauna, especially the Finnish kind, heats the body to 80–100°C. Within minutes, your heart rate climbs, blood vessels dilate, and you start to sweat profusely. This mimics mild cardiovascular exercise, where the heart rate can reach 120–150 beats per minute, similar to a brisk jog.
Afterward, plunging into icy water (often below 10°C) causes the opposite response. Skin vessels constrict, blood rushes to the core, and stress hormones surge. Your sympathetic nervous system is activated almost instantly. This cycle puts your circulatory system through a dynamic workout.
Together, heat and cold exposures create a form of physiological contrast training. But does this translate to actual improvements in health and longevity?
Some of the most compelling evidence for lifespan benefits comes from long-term studies of regular sauna users in Finland. Men who used the sauna four to seven times per week had nearly half the risk of dying from cardiovascular causes (heart attack, stroke, or sudden cardiac death) compared to those who went just once a week. All-cause mortality was also lower in the frequent sauna group.
The benefits are not limited to heart health. Frequent sauna use has been associated with significantly reduced risk of Alzheimer’s disease and other forms of dementia. There is also growing evidence that it may lower the risk of developing depression and psychosis. In some studies, sauna exposure even helped patients with severe depressive symptoms regain appetite and improve mood.
Why might these outcomes occur? One theory is that passive heat exposure triggers a controlled stress response, stimulating protective adaptations. Heat shock proteins, which are activated during sauna use, may help protect cells and reduce inflammation. Repeated sessions appear to improve blood vessel function, reduce arterial stiffness, and lower blood pressure, all of which are linked to healthier aging.
Regular sauna use has also shown potential for improving glucose metabolism. For individuals with or at risk for type 2 diabetes, this means better insulin sensitivity and reductions in long-term blood sugar markers. Some studies even suggest sauna users report fewer common colds over time.
Overall, sauna use checks many boxes for supporting longevity: better cardiovascular function, improved metabolic control, and possible cognitive protection.
Cold exposure, while less studied than sauna use, offers a different kind of physiological challenge. Instead of relaxation and dilation, the focus is stimulation and constriction. Immersion in cold water causes an immediate surge in norepinephrine, a hormone that increases alertness and readiness. Over time, this repeated exposure may build resilience to stress and improve mood regulation.
It also activates brown adipose tissue, or brown fat, which burns calories to produce heat. This thermogenic activity is associated with improved insulin sensitivity, lower body fat, and better overall metabolic function. Cold exposure has also been linked to reduced systemic inflammation, which is a key driver of aging.
Animal research has revealed that exposure to mild cold environments can be associated with increased lifespan, likely due to lower core body temperatures and reduced metabolic strain. However, it is important to note that these findings do not yet translate directly to humans, and more evidence is needed.
That said, the potential for cold to act as a hormetic stressor, providing a beneficial challenge that the body adapts to over time, adds to its growing appeal.
In traditional Finnish practice, sauna use is rarely a standalone activity. It is often followed by an icy plunge into a lake or snowbank. This hot-to-cold contrast produces a dramatic physiological effect: heart rate drops quickly, blood vessels constrict, and the autonomic nervous system resets.
There is some evidence to suggest that this combination may train the vascular system more effectively than either exposure alone. Alternating between hot and cold could enhance blood flow, improve circulation, and build cardiovascular flexibility. Some also report benefits in immune resilience and mental clarity, though these claims are still largely anecdotal.
Despite centuries of tradition, the science specifically investigating the combination of sauna and cold therapy is still limited. Most existing studies focus on each element in isolation. Future research may shed light on whether the pairing creates synergistic benefits, or whether it simply feels invigorating.
Although the research supporting sauna and cold exposure is promising, it is important to keep perspective. Many of the strongest studies are observational. They can highlight associations but cannot prove causation.
For example, people who use saunas frequently may also have more free time, higher income, and greater access to healthcare. These factors are known to improve health outcomes and could influence the data. In addition, many studies focus on Finnish men, which limits the ability to generalize results to women or diverse populations.
Reverse causation is also a possibility. Healthier people are more likely to use saunas and cold plunges regularly, while those with serious health conditions may avoid them. This can skew findings in favor of these practices.
While the health risks are generally low, sauna bathing and cold plunging are not for everyone. People with unstable cardiovascular conditions, high blood pressure, or certain medications should speak with a doctor before trying either. Alcohol use, dehydration, and preexisting illness can all increase the danger.
Sauna:
Cold Plunge:
Combining the Two:
The tradition of sauna and cold exposure is more than folklore. Mounting evidence suggests that these contrasting therapies can support key pillars of longevity: cardiovascular health, metabolic resilience, cognitive function, and emotional well-being.
However, while the data are encouraging, they are not definitive. These practices should be seen as part of a broader lifestyle approach that includes exercise, good nutrition, sleep, and social connection. Sauna and cold plunge may not be miracle cures, but they could be powerful allies in the quest to age well.
