Hot tub health benefits outweigh saunas, new study finds

Saunas have become a go-to wellness trend for recovery and longevity, but most people don’t have regular access to one. A new study from the University of Oregon suggests that a simple soak in a hot tub or deep hot bath may deliver many of the same physiological advantages — and in some ways, even more pronounced effects than saunas.

Researchers compared three passive-heat methods and measured how each changed body temperature, circulation, heart performance, immune markers, and inflammation. Their findings point to hot-water immersion as a powerful, widely available option for boosting cardiovascular and inflammatory responses, especially for people who can’t easily get into a sauna.

How the study was set up and who participated

The trial, published in the American Journal of Physiology, directly compared three commonly used heat therapies. The team tracked participants before, during, and after:

• Hot-water immersion (a deep soak in hot bath or tub)
• Dry heat (a traditional sauna-like environment)
• Far-infrared sauna exposure

Twenty healthy, physically active adults between 20 and 28 years old took part, with an even split of men and women. Investigators monitored core body temperature, blood pressure, heart rate, cardiac output (how much blood the heart pumps each minute), circulating immune cell counts, and inflammatory cytokines in blood samples. The aim was to isolate immediate physiological responses to each heating modality in a young, fit population.

Biggest changes came from hot-water immersion

The most striking outcome: soaking in hot water raised core temperature the most and triggered the strongest cardiovascular and immune responses. Compared with dry air and far-infrared exposure, immersion produced larger increases in heart rate and cardiac output and elevated certain inflammatory signaling molecules and immune cell shifts that the other treatments did not.

Lead researchers explained that core temperature is the primary driver behind these downstream changes. The higher the internal temperature becomes, the more the body adjusts circulation and immune signaling — responses that are linked in other studies to improved vascular health and reduced long-term risk of chronic disease.

Why a hot bath heats you differently than a sauna

The physics and physiology are straightforward. When the body is submerged in hot water, heat moves by conduction across the skin much more efficiently than through hot air. Submersion also keeps sweat from evaporating effectively, so the body retains heat instead of cooling itself. Two additional physiological mechanisms matter:

• Hydrostatic pressure: Water pressing on the body increases venous return to the heart, which can boost cardiac output and circulation.
• Reduced evaporative cooling: Submersion limits sweating effectiveness, allowing core temperature to climb higher and faster.

Those factors combine to make hot tubs and deep baths particularly potent for raising internal temperature and driving cardiovascular adaptations.

How these heat effects relate to exercise and long-term health

There’s a growing body of evidence—much of it from long-term sauna studies in Finland—that regular passive heat exposure can lower blood pressure, reduce inflammation, and correlate with longevity and lower cardiovascular risk. Saunas have a strong research base, especially from Finnish cardiologist Dr. Jari Laukkanen, who has linked frequent, longer sauna sessions to improved heart outcomes.

This Oregon study suggests hot-water immersion can replicate several of those exercise-like cardiovascular responses, and in a young, healthy group it did so more quickly than sauna sessions. That makes heat therapy an intriguing option for people who cannot do aerobic exercise because of injury, mobility issues, or other limitations. Still, investigators and clinicians caution that while heat can mimic aspects of aerobic activity, it doesn’t replace the full range of benefits from regular physical exercise.

Safety tips and practical guidance for using heat therapy

Heat interventions can be beneficial, but they should be used carefully. Key safety points include:

• Check with a healthcare provider if you have heart disease, low or high blood pressure, diabetes, are pregnant, or take medications that affect heat tolerance.
• Start gradually: shorter sessions at moderate temperatures before increasing duration or heat.
• Stay hydrated and avoid alcohol or heavy meals right before a session.
• Limit session length based on comfort and medical advice; overheating and fainting are real risks.
• Consider supervisor presence or a gradual cool-down if you’re trying heat therapy for the first time.

Researchers emphasize moderation: used safely and consistently, passive heat can support cardiovascular health, but misuse or overexposure carries risks.

What’s still unknown and where research is heading

The study offers a controlled snapshot of immediate physiological reactions in young adults, but broader questions remain. Future investigations need to test older adults, people with chronic conditions, and varied frequencies and durations of exposure to determine long-term outcomes. Researchers also want to explore whether repeated hot-bath sessions can deliver the same longevity and heart-disease protections observed in long-term sauna studies.

Study authors and other experts agree that passive heating shows promise as a low-barrier intervention for improving vascular function and some immune markers, but they stress more diverse and longer-term trials are necessary to define optimal protocols and safety thresholds.

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Michael Thompson

Michael Thompson is an experienced journalist covering U.S. and global news. With ten years on the front lines, he breaks down political and economic stories that matter. His precise writing and keen attention to detail help you grasp the real‑world impact of every event.