One might think that an island nation that's essentially a wet and windy rock with average year round temperatures in the low 40s and prevalent darkness for seven months out of the year, would be a hard place to stay healthy. But the people of Iceland don't just stay healthy, they master it. At 83.1 years, Iceland's life expectancy is higher than almost every other country in the world, even those that are much warmer, richer and more educated.

So what is Iceland's secret? Is it good genes or good living?

In a recent NBC News story, reporters interviewed Kari Stefansson, founder of DeCode Genetics, a company that has collected genetic data on about one-third of Iceland's residents. When the researchers at DeCode compared the gene pool of Icelandic nonagenarians, they found that they were more closely related to one another than they were to a control group from the rest of the Icelandic population. Their conclusion? Longevity is in the genes.

But there are many others who think that Icelanders' clean living contributes to their long lives. The Icelandic diet consists mainly of fish and lean meats, although the shortened growing season means that fruit and veggies aren't a staple. Iceland boasts low pollution levels and an athletic lifestyle that includes swimming, hiking, rock climbing and kayaking.

Iceland also has some of the lowest rates for obesity, infant mortality and tobacco use worldwide. And according to the Organisation for Economic Co-operation and Development (OECD), Iceland devotes more resources to health care than most other industrialized nations.

While they may have a prevalence towards longer living, Icelanders also live a lifestyle that would support good health well into their senior years.

So the secret is no real secret after. It's most likely a combination of hearty Viking genes and active, healthy living that helps Icelanders live their lives to the fullest.

Why do people from Iceland live so long?
Researchers debate whether it's genetics or clean living that helps Icelanders live such long, healthy lives.