The short answer, for men anyway: Be born in Iceland.

Icelandic men have apparently surpassed Japanese men in life expectancy. Researchers aren’t sure why, but the men on the Nordic island-nation hang in there an average of 79.4 years, compared to 78.6 in Japan.

Lifespan stats can be misleading, however, and were especially so in the past when many children died young, dragging the averages way down. Even today, life expectancy is an average number that masks large differences between the rich (who have access to the best health care) and the poor, as well as between people who eat well and exercise vs. those who don’t.

Whatever, it’s likely the Icelandic feat has something to do with diet, lifestyle, and available health care. In the United States, male life expectancy is 75.2 years (as of 2004; preliminary 2005 stats here.) Americans are living longer, but we’re not keeping up with advances in other countries.

Part of the problem in the U.S., too, seems to be how we spend our health care dollars. We’re last among 19 industrialized nations in preventable deaths. We spend a fortune on health care, but it’s not working — an irony glossed over in the politicized health care debate. Our Bad Medicine Columnist Chris Wanjek notes:

The United States has by far the highest level of health spending per capita in the world: nearly $6,100 or 15.4 percent of the GDP, according the World Health Organization. Scandinavian countries, with their universal healthcare coverage, pay less than half of this.

Yet the United States has one of the lowest life expectancies among developed nations, at about 78 years, which is lower than Cuba’s and marginally beats Slovenia, according to United Nation’s figures.

That figure of 78 years is the average, including men and women (in all countries, women live longer). And why is that? Nobody knows for sure, but hormones seem to play a role. And one idea put forth a couple years back is that competing for a mate wears us out.

To live really long, you really want to born female in Japan, where you can expect to spend 86 years pondering all this.

If the headline of this blog had you expecting tricks to get you to 100 or 1,000, see our special report on Immortality.