Sitting in a hot, sweaty room for a few minutes a day might be one of the most powerful ways to protect your heart, delay dementia, and even combat depression. For decades, medical experts feared that the intense heat of a sauna was dangerous for the cardiovascular system. In 1976, a British Army physician even blamed the Finnish sauna for an epidemic of fatal heart attacks among middle-aged men in Finland. However, modern scientific evidence suggests he had it completely backward. Frequent heat exposure is not a hazard; instead, it is a potent therapeutic tool.
The turning point in our understanding of heat came from a long-term study in Finland. In the mid-1980s, researchers at the University of Kuopio enrolled about 2,600 middle-aged men to study cardiovascular disease. In 2015, cardiologist Jari Laukkanen examined the participants' sauna habits and compared them with their health outcomes over two decades. The results were startling. Men who used a sauna four to seven times a week experienced a 63 percent reduction in fatal heart attacks and a 40 percent reduction in all-cause mortality compared to those who went only once a week.
This benefit exists because heat stress mimics the effects of exercise. When you sit in a sauna, your heart rate accelerates, blood vessels dilate, and blood flow increases. To cope with the fluid lost through sweating—which can exceed one liter per hour—the body expands its blood plasma volume. This cardiovascular workout helps reduce blood pressure and activates the parasympathetic nervous system, which promotes rest and recovery.
But the benefits of heat therapy extend far beyond the heart; they also reach the brain. The Kuopio study found that the most frequent sauna users had a 63 percent lower risk of developing Alzheimer's disease. This finding was supported by another Finnish study of 14,000 people, which showed that using a sauna nine to twelve times a month cut the risk of Alzheimer's diagnoses in half over 20 years.
A remarkable real-world example of this protection is the story of Doug Whitney. Whitney carried a genetic mutation that practically guaranteed he would develop Alzheimer's by his early 50s. Yet, he remained cognitively healthy well into his late 70s. The secret to his resilience appeared to be his career: he worked for decades as an engine-room mechanic on naval ships, where temperatures routinely exceeded 50°C (122°F). When researchers analyzed Whitney’s cells, they discovered exceptionally high levels of "heat shock proteins." These proteins act as cellular caretakers, maintaining cell structure and clearing away misfolded proteins—such as tau and amyloid—that typically accumulate and cause Alzheimer's disease.
Heat also shows promise in bolstering mental health. Finnish studies noted that frequent sauna users had a lower lifetime risk of psychosis. More recently, researchers have investigated "whole-body hyperthermia"—deliberately raising a person's core temperature—as a treatment for depression. In one clinical trial, patients with severe depression who had their core temperature warmed to 38.5°C (101°F) reported a 30 percent reduction in symptoms, a benefit that lasted up to six weeks. Animal studies suggest that heating the brain stimulates the dorsal raphe nucleus to produce serotonin, the neurotransmitter targeted by many antidepressant medications.
While scientists are still working to determine the optimal "dose" of heat therapy, the current evidence is highly encouraging. For those without access to a sauna, hot tubs and warm baths appear to offer similar rewards. A study of 30,000 Japanese adults found that those who took hot baths almost daily had a 25 percent lower risk of death from cardiovascular disease. Whether through a traditional Finnish sauna or a simple hot bath, incorporating heat therapy into our daily routines could be a vital step toward a longer, healthier life.