With temperatures between -110 and -166°F induces stress on the body and the sirtuins work better, especially in the brown fat in the abdominal and back areas. Cold appears to turn on the longevity genes. 

Hot Vs. Cold

No sauna studies have shown convincingly that temporary heat exposure may be good for us, but a study from Finland in a group of more than 2300 middle-age men for more than 20 years showed that those who used the sauna with great frequency-up, to seven times  per week, enjoyed a two fold drop in heart disease, fatal heart attacks, and all- cause mortality over those who heat-bathed once per week.