Sauna bathing and mortality risk: unraveling the interaction with systolic blood pressure in a cohort of Finnish men.

Plain-language summary

This study followed 2,575 Finnish men aged 42 to 61 for a median of 27.8 years and asked whether sauna habits change how dangerous high blood pressure is. Over that time 1,618 of them died. Men with high systolic blood pressure (the top number, the pressure in your arteries when the heart beats) were 29% more likely to die than men with normal readings. Men who used the sauna twice a week or less were 16% more likely to die than men who used it three to seven times a week. The interesting result is the combination. Men with high blood pressure who rarely used the sauna were 47% more likely to die than men with normal pressure who used it often. Men with high blood pressure who did use it often showed no statistically reliable increase at all. This is an observational cohort in a country where sauna use is universal, so the men who go three times a week differ from those who do not in ways no study can fully adjust for. It cannot show that the sauna itself is what made the difference.

Key findings

• High systolic blood pressure was associated with a 29% higher risk of dying from any cause.
• Using the sauna twice a week or less was associated with a 16% higher risk than using it three or more times a week.
• High blood pressure combined with infrequent sauna use carried a 47% higher risk than normal blood pressure with frequent use.
• High blood pressure combined with frequent sauna use showed no statistically reliable increase in risk.