Saunas are common in Norway, even if not to the same degree as in Finland. The reason Finland has had a lower life expectancy than Norway is believed to be due

Saunas are common in Norway, even if not to the same degree as in Finland. The reason Finland has had a lower life expectancy than Norway is believed to be due to the difference in diet (cardivascular issues). Note that the diet in Finland has changed quite a lot over the last decades and these differences will presumably level out, statistically.