Study leader Prof. Jari Laukkanen, of the University of Eastern Finland, and team recently published their findings in the journal Age and Ageing.
According to Alzheimer's Disease International, there are around 46.8 million people worldwide living with dementia. Unless new prevention and treatment strategies are found, this number is expected to reach 131.5 million by 2050.
Previous studies have suggested sauna use may benefit cardiovascular health, but Prof. Laukkanen and team note that no studies had investigated whether sauna use might benefit memory disorders.
To find out, the researchers analyzed the data of 2,315 apparently healthy men aged 42-60 who were part of the Kuopio Ischaemic Heart Disease Risk Factor Study.
The team divided the men into three groups based on their frequency of sauna use: once a week, two to three times a week, and four to seven times a week.
Participants were followed-up for a median of 20.7 years, during which time 204 cases of dementia and 123 cases of Alzheimer's disease - the most common form of dementia - were diagnosed.
Frequent sauna use lowered dementia risk by 66 percent
The researchers found that men who used a sauna more frequently were at lower risk of dementia, with the risk reducing further with more frequent sauna use.
Compared with men who used a sauna once a week, men who used a sauna four to seven times weekly were found to be at 66 percent lower risk of any dementia and had a 65 percent lower risk of developing Alzheimer's disease.
These results remained after accounting for a number of potentially confounding factors, including participants' age, alcohol intake, smoking status, body mass index, previous heart attack incidence, and diagnosis of type 2 diabetes.
Commenting on their findings, the authors write:
"In this male population, moderate to high frequency of sauna bathing was associated with lowered risks of dementia and Alzheimer's disease. Further studies are warranted to establish the potential mechanisms linking sauna bathing and memory diseases."
A previous study from Prof. Laukkanen and colleagues associated frequent sauna use with reduced risk of death from cardiovascular disease.
The researchers speculate that sauna use increases heart rate in a way that is comparable to exercise, which benefits heart health. This same mechanism could also be beneficial for memory, the team suggest.
"The sense of well-being and relaxation experienced during sauna bathing may also play a role," adds Prof. Laukkanen.
While the study results are certainly interesting, some glaring limitations should be noted. Firstly, the study only included men, so the results cannot be generalized to women. Additionally, very few participants reported never having used a sauna, so it is unclear how frequent sauna use might affect dementia risk in comparison to having never used one.
Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men, Jari Laukkanen et al., Age and Ageing, doi: 10.1093/ageing/afw212, published online 7 December 2016, abstract.
University of Easter Finland news release, accessed 19 December 2016 via AlphaGalileo.
Additional source: Alzheimer's Disease International, Dementia statistics, accessed 19 December 2016.