What Temperature and Duration Did the KIHD Sauna Study Use?

The 2015 KIHD study in JAMA Internal Medicine followed 2,315 men aged 42–60 from Eastern Finland. Participants described their sauna habits at baseline using a questionnaire. Reported averages were approximately 79°C, 14.2 minutes per session and 2.1 sessions per week.

The researchers compared groups with different reported frequencies and durations. They observed associations between more frequent sauna bathing and lower rates of several mortality outcomes. The study did not randomly assign sauna routines, establish causation or validate a universal temperature–duration–frequency prescription.

See the separate cardiovascular research discussion and brain-health research discussion for those topics. Findings about one population and outcome should not be assumed to apply to every person or sauna type.

Why the Temperature Number Needs Context

The study’s room-temperature information was self-reported. It did not establish the precise ceiling-sensor-to-head-or-foot temperature conversions previously presented on this page. Temperature varies within a sauna and with the equipment, measurement position and ventilation; use the equipment’s instructions rather than subtracting a fixed number from a thermostat reading.

Different humidity, steam exposure, seating position and sauna designs also limit comparisons based on a single temperature number. An observational study average is not a safety threshold.

What the Study Does Not Establish

The earlier “health-optimized” routine and week-by-week progression on this page have been withdrawn. The cited cohort does not validate that complete routine, an individual therapeutic dose, a prescribed cold plunge or a universal fluid-replacement schedule.

Reported associations in participants who used saunas more often do not mean that increasing heat, time or frequency is beneficial or safe for a particular reader. Existing health, fitness and other differences between participants can affect observational findings even when researchers adjust for measured factors.

Traditional Practice and Personal Safety

Descriptions of Finnish traditions are cultural context, not evidence that a particular multi-round routine or heat-to-cold transition is appropriate for everyone. Sauna use should not be treated as an endurance test.

Follow the selected sauna and heater manufacturer’s safety instructions. A qualified healthcare professional can advise on personal suitability, including health conditions, medication, pregnancy and use by children. Avoid alcohol with sauna use and leave the heat if you feel unwell; do not stay in to reach a target duration from an article.

This page explains study design and limitations. It does not replace individual medical advice or the equipment’s operating instructions.

Sources and Correction

October 16, 2026: removed unsupported optimal-protocol claims, fixed temperature-measurement inferences and distinguished observed habits from individualized advice. ThermalFinn has not performed clinical testing of a sauna routine.