Narrative review weighs cardiovascular evidence for sauna and hot-bath habits across 45 studies

Researchers searched two major databases and synthesized findings from 45 studies examining how regular sauna use and domestic hot-water bathing relate to cardiovascular and systemic health markers. Evidence for sauna was stronger and more consistent, while support for home bathing rested largely on observational data tied to intermediate biological measures.

What the study found

The review drew on 28 sauna studies and 17 bathtub-bathing studies. The bodies of evidence differed substantially in design and depth, and the authors are careful to frame associations rather than causal relationships throughout.

For sauna use, the strongest signals came from large Finnish prospective cohort studies, which associated frequent sauna habits with lower rates of cardiovascular and all-cause mortality, as well as more favorable markers of inflammation and endothelial function. These prospective data represent the more methodologically robust portion of the review.

Evidence for domestic hot-water bathing — drawn predominantly from Japanese research — was more limited. Studies in that literature reported associations between habitual bathing and lower arterial stiffness, better blood-sugar regulation, and shifts in certain inflammatory or stress-related markers. However, these findings come mainly from observational designs and measure intermediate biological endpoints rather than hard clinical outcomes.

Both practices appear to trigger overlapping physiological responses: rising core body temperature, widening of peripheral blood vessels, and activation of heat shock proteins. The review notes that individual factors such as age, sex, and cultural context appear to shape how these responses play out, and the authors call for future work with more precisely defined exposure parameters and clinically meaningful endpoints.

Limits worth knowing

As a narrative rather than systematic review, the synthesis does not apply formal quality scoring or meta-analytic pooling, which limits the strength of any comparative conclusions. The sauna literature is heavily concentrated in Finnish cohorts, and the bathing literature in Japanese populations, so generalizability to other groups is uncertain. Studies involving children and pregnant or postpartum women were excluded, narrowing the applicable population. Funding sources for the review itself are not described in the abstract. Exposure definitions — how often, how long, and at what intensity participants bathed or used saunas — varied across included studies, complicating direct comparison.

About this entry. The Heartwood Review summarizes published, peer-reviewed research in its own words and links to the original source. It is not medical advice; consult a physician before beginning or changing any thermal or recovery practice. Findings summarized here describe the study cited, not any product sold by Teak & Marble Atelier. Corrections.