This study included 2315 men between the age of 42 and 60 years (Laukkanen T, et.al., 2015).
The purpose of the research was to investigate the association of frequency and duration of sauna bathing with the risk of sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease, and all-cause mortality.
Men who used the sauna for 4 to 7 sauna bathing sessions per week had a reduction of 63% for sudden cardiac death. Similar associations were found for fatal coronary heart disease, fatal cardiovascular disease and all-cause mortality.
A temperature of 174 degrees Fahrenheit for a minimum of 20 minutes has been shown to give the best results.
Tanjaniina Laukkanen 1, Hassan Khan 2, Francesco Zaccardi 3, Jari A Laukkanen. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med. 2015 Apr;175(4):542-8.