Sauna and cold exposure: what does science say about heat and cold therapy?

Sauna and cold exposure aren't new — they're thousands of years old. But only in the last decade has science begun to seriously quantify their effects. The results are striking: regular sauna use is associated with a dramatic reduction in cardiovascular mortality, while cold exposure produces a sustained rise in dopamine and improved immunity.

What effect does sauna have?

The landmark Finnish study by Laukkanen et al. (2015, JAMA Internal Medicine) followed 2,315 men for an average of 20.7 years. Finding: men who used the sauna 4–7 times per week had, compared to those who used it once per week:

Laukkanen et al. (2018, BMC Medicine) extended the finding to 1,688 men and women, confirming that cardiovascular mortality risk decreased linearly with frequency of sauna use — with no threshold. More = better.

A review in Mayo Clinic Proceedings (Laukkanen et al., 2018) summarized the mechanisms: sauna reduces arterial stiffness, decreases inflammation and oxidative stress, stabilizes the autonomic nervous system, improves lipid profiles, and lowers blood pressure. Bartlett et al. (2024, Journal of Applied Physiology) confirmed in a randomized controlled trial that 8 weeks of regular sauna use improves vascular health in patients with coronary artery disease.

Laukkanen et al. (2023, Journal of Nutrition, Health and Aging) additionally showed that regular sauna negates the adverse effect of elevated blood pressure on mortality — meaning sauna is especially beneficial for hypertensives.

Brunt et al. (2025, European Journal of Preventive Cardiology) confirmed in a systematic review and meta-analysis that passive heat therapy (including sauna) improves cardiometabolic parameters: blood pressure, body weight, fasting glucose, and HbA1c.

How does cold exposure affect the body?

When you enter cold water, a cascade of neurotransmitters is triggered. Søberg et al. (2023, Cell Reports Medicine) showed that cold exposure causes a sustained dopamine increase — up to 250% above baseline, lasting several hours. This means improved mood, focus, and motivation, without the "crash" of caffeine.

Espeland et al. (2023, International Journal of Circumpolar Health) confirmed in a systematic review positive effects on immune response, reduced inflammation, and improved circulation. However, they caution that evidence quality is still limited — most studies are small, without control groups.

Søberg's research additionally showed that cold exposure improves insulin sensitivity and glucose metabolism and activates brown adipose tissue — a type of fat that burns energy instead of storing it. Patrick & Johnson (2021, Experimental Gerontology) confirmed this mechanism in the context of healthy aging.

Practical protocols

Sauna: 80–100°C, 15–20 minutes, 2–4× per week (Laukkanen et al., 2015; 2018). Ideally after training — sauna post-workout doesn't impair muscle recovery, while simultaneously promoting vasodilation and release of heat shock proteins (HSPs) that protect cells from stress.

Cold exposure: 10–15°C, 1–3 minutes, 2–4× per week. Huberman (2024) recommends starting conservatively (15°C) and gradually lowering temperature. The dopamine effect occurs even with brief exposure — no need for extreme temperatures or extended durations.

Combination: The classic Nordic approach: sauna → cold → sauna → cold. This cyclically loads the vascular system in a way comparable to interval training for arteries (Laukkanen et al., 2018, BMC Medicine).

Warning: Do not use cold exposure immediately after resistance training if the goal is muscle hypertrophy — cold within the first 2 hours post-training can blunt the anabolic response (Roberts et al., 2015, Journal of Physiology). Perform cold exposure on non-training days or at least 4+ hours after training.

References

• Bartlett, D.B. et al. (2024). Finnish sauna bathing and vascular health in adults with coronary artery disease: a randomized controlled trial. Journal of Applied Physiology, 136(4).
• Brunt, V.E. et al. (2025). Non-acute effects of passive heating interventions on cardiometabolic risk: systematic review and meta-analysis. European Journal of Preventive Cardiology.
• Espeland, D. et al. (2023). Health effects of voluntary exposure to cold water: a systematic review. International Journal of Circumpolar Health, 81(1).
• Huberman, A. (2024). The science of cold exposure for health and performance. Huberman Lab Podcast.
• Laukkanen, J.A. et al. (2018). Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clinic Proceedings, 93(8), 1111–1121.
• Laukkanen, J.A. et al. (2023). The interplay between systolic blood pressure, sauna bathing, and cardiovascular mortality. Journal of Nutrition, Health and Aging, 27(5), 348–353.
• Laukkanen, T. et al. (2015). Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine, 175(4), 542–548.
• Laukkanen, T. et al. (2017). Sauna bathing is inversely associated with dementia and Alzheimer's disease. Age and Ageing, 46(2), 245–249.
• Laukkanen, T. et al. (2018). Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women. BMC Medicine, 16(1), 219.
• Patrick, R. & Johnson, T.L. (2021). Sauna use as a lifestyle practice to extend healthspan. Experimental Gerontology, 154, 111509.
• Roberts, L.A. et al. (2015). Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. Journal of Physiology, 593(18), 4285–4301.
• Søberg, S. et al. (2023). Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine, 2(10), 100408.