Frequent sauna use went with fewer heart deaths in men and left the question open for women
This 2018 BMC Medicine paper is the only Kuopio study of sauna and cardiovascular deaths that includes women. It followed 1,688 people for 15 years, and its title claims the link for men and women alike.
The paper
Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study
Laukkanen T, Kunutsor SK, Khan H, Willeit P, et al.. BMC Medicine, 2018;16(1):219.
See the study at a glance
- Design
- Prospective cohort study
- People
- 1,688 people (867 women, 821 men)
- Who they were
- Adults aged 53 to 74 (average 63) were examined in Kuopio between 1998 and 2001. The men came from the original study group, and the women joined at this examination.
- What they did
- A questionnaire asked people how many sauna sessions they took a week and how many minutes those added up to. Frequency ran from once a week up to four to seven times, and sauna temperatures averaged 75.9°C.
- How long
- Median 15.0 years
These numbers came out of it
0.36
Men and women who went four to seven times a week had this hazard ratio for cardiovascular death compared with people who went once. Anything under 1.00 means lower risk.
0 of 73
None of the 73 women who went four to seven times a week died of cardiovascular disease, so the paper had no ratio to estimate.
1.00
Women who went two or three times a week had the same estimated risk of cardiovascular death as women who went once.
8 of 8
All eight people in the combined top group who died of cardiovascular disease were men.
Hazard ratio for cardiovascular death with 95% confidence interval
The link showed up in men, and women at two or three sessions a week came out at 1.00
The paper's Model 3 adjusted for age, sex, body mass index, smoking, systolic blood pressure, LDL cholesterol, alcohol, previous heart attack, type 2 diabetes, physical activity and socioeconomic status. The chart has no row for women who went four to seven times a week because none of them died of cardiovascular disease.
The researchers did this
Women joined the Kuopio study at its 1998 to 2001 examination. That round drew a random sample of 2,358 people aged 53 to 74, and 1,774 took part. This paper analyzed the 1,688 with complete sauna data (867 women and 821 men) and tracked cardiovascular deaths among them through 2015.Source 1 · Cohort studySauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort studyLaukkanen T, Kunutsor SK, Khan H, et al.. BMC Medicine, 2018.Read the paper ↗PubMed ↗
There were 181 cardiovascular deaths. For every 1,000 weekly bathers followed for a year, 10.1 died of cardiovascular disease, and in the top group the figure was 2.7. With age, sex, lifestyle and socioeconomic status taken into account, the top group's hazard ratio was 0.36.Source 1 · Cohort studySauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort studyLaukkanen T, Kunutsor SK, Khan H, et al.. BMC Medicine, 2018.Read the paper ↗PubMed ↗
In men, four to seven sessions a week carried a hazard ratio of 0.39, and all 8 deaths in the combined top group were men. For women who went two or three times a week, the hazard ratio against women who went once was 1.00. None of the 73 women in the top group died of cardiovascular disease, so the paper couldn't estimate their risk. A formal test found no significant difference between the sexes.Source 1 · Cohort studySauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort studyLaukkanen T, Kunutsor SK, Khan H, et al.. BMC Medicine, 2018.Read the paper ↗PubMed ↗
Frequent bathers were far more likely than weekly bathers to live in a family house. In the top group, 70.7% lived in one and 19.0% in an apartment block. Among weekly bathers those figures were 23.4% and 60.1%, and the weekly bathers were also older and more often women.Source 1 · Cohort studySauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort studyLaukkanen T, Kunutsor SK, Khan H, et al.. BMC Medicine, 2018.Read the paper ↗PubMed ↗ When the researchers added sauna frequency to a standard risk model, its prediction score (the C-index) moved from 0.7716 to 0.7807.
The study can't tell you these things
- The women's results come from 63 deaths. None were in the top group, so the paper can't estimate an effect for women either way.
- Frequent bathers lived in family houses far more often than weekly bathers and less often held university degrees. Sauna frequency may partly stand in for where and how people lived, and the paper didn't test that.
- Another model left out people who had coronary heart disease at the start. It used a different sample, so its hazard ratio of 0.23 can't be compared directly with the others.
- Only 43 people never used a sauna, so weekly bathers had to serve as the comparison group.
- People reported their sauna habits once. When the men in the study answered again 11 years later, their habits had changed.Source 2 · Cohort studyFinnish sauna bathing does not increase or decrease the risk of cancer in men: A prospective cohort studyLaukkanen JA, Mäkikallio TH, Khan H, et al.. European Journal of Cancer, 2019.Read the paper ↗PubMed ↗
People quote it like this
The title says sauna bathing is linked to reduced cardiovascular mortality in men and women. A later Kuopio paper wrote that results in women were likely to be similar.Source 3 · Cohort studyInflammation, sauna bathing, and all-cause mortality in middle-aged and older Finnish men: a cohort studyKunutsor SK, Jae SY, Kurl S, et al.. European Journal of Epidemiology, 2022.Read the paper ↗PubMed ↗ This paper's own figures show no link in women at two or three sessions a week and no estimate for the top group.
We cited these sources
- 01Laukkanen T, Kunutsor SK, Khan H, Willeit P, Zaccardi F, Laukkanen JA. Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study. BMC Medicine. 2018;16(1):219. doi:10.1186/s12916-018-1198-0 PMID 30486813
- 02Laukkanen JA, Mäkikallio TH, Khan H, Laukkanen T, Kauhanen J, Kunutsor SK. Finnish sauna bathing does not increase or decrease the risk of cancer in men: A prospective cohort study. European Journal of Cancer. 2019;121:184-191. doi:10.1016/j.ejca.2019.08.031 PMID 31590079
- 03Kunutsor SK, Jae SY, Kurl S, Kauhanen J, Laukkanen JA. Inflammation, sauna bathing, and all-cause mortality in middle-aged and older Finnish men: a cohort study. European Journal of Epidemiology. 2022;37(12):1225-1231. doi:10.1007/s10654-022-00926-w PMID 36255556