What 40 sauna studies can tell us
An overview of the evidence, from traditional sauna to infrared heat, and why the details matter.
Worth knowing: A review from 2018, with a literature search up to April 2017: a snapshot of the research at that time, not an up-to-date answer.
The short version
This 2018 systematic review gathered 40 studies of regular dry sauna bathing, with 3,855 participants in total, including both traditional Finnish and infrared sauna. The authors reported promising findings in several areas, such as blood pressure, heart failure symptoms and pain in rheumatic conditions. But many of the studies were small, only 13 were randomized trials, and only three of those were judged to have a low overall risk of bias. It is a useful map of the research up to April 2017, not a final answer.
Keep in mind
Many of the studies were small, and most had a high or unclear risk of bias. Finnish and infrared sauna are counted together, so the results cannot be read as one established routine.
What they found
The review reported promising findings in several areas, including blood pressure, heart failure symptoms and pain in rheumatic conditions.
It also found large differences between the studies: in who took part, the kind of sauna, how often and how long people used it, and what was measured. Those differences made it hard to combine the results into one overall answer.
Most studies had a high or unclear risk of bias. Of the 13 randomized trials, only three were judged to have a low overall risk of bias.
What this means for your practice
There is plenty here to be curious about, and good reason to be careful. The review points to questions worth studying further, not to a routine that has been shown to work.
This does not establish a sauna routine to follow, and it is not evidence for the effects of KUUME’s guided sessions.
Methods and limitations
What the researchers did
The researchers searched the published research, up to April 2017, for clinical studies of regular dry sauna bathing. They found 40 studies with 3,855 participants in total, and judged each study’s risk of bias: how likely its design was to skew the result.
A systematic review is a study of studies. Instead of testing sauna on a new group of people, it collects and compares the research that already exists, following a set method. The 40 studies used different designs; 13 of them were randomized controlled trials.
The review covers both traditional Finnish sauna and infrared sauna. Results from one kind of heat do not automatically carry over to the other.
How much can this tell us?
A review is a good place to start because it shows the whole landscape rather than one headline. But it can only be as strong as the studies it gathers, and here many of them were small or had design problems. A review’s title alone does not make its conclusions certain.
It is also a snapshot. The review was published in 2018 and searched the literature up to April 2017, so research published since then is not part of it.
What makes it useful
- A systematic search, with a risk-of-bias judgment for each study
- 40 studies and 3,855 participants in one place
- Open about how uncertain the evidence is
What limits it
- Most included studies had a high or unclear risk of bias
- 13 of 40 studies were randomized trials; three had a low overall risk of bias
- Finnish and infrared sauna are combined, and outcomes varied widely
- Covers research up to April 2017
Where this study fits
Where this study fits
We score claims, not single studies. This one is part of the evidence for:
Regular sauna means fewer deaths from heart disease. Some support
Low certaintyLarge effectIllness and death
Heat therapy helps people with heart failure. Some support
Low certaintySize not reportedBody signals
Read the original
Hussain J, Cohen M. Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review. Evid Based Complement Alternat Med. 2018;2018:1857413.
DOI 10.1155/2018/1857413 · PubMed 29849692