Speculation abounds. Could it be the stimulation of the city which somehow stirs its population to want to live? Are the cultural offerings so enticing that New Yorkers are inspired to stay alive to indulge? Or is it the city-wide ban on trans fats?
I'm sure it'll be a few years before the studies are published, but the obvious conclusion of many people, including myself, is that NYC's longevity factor is directly related to the way its people transport themselves. Few New Yorkers own cars. Why would they? Mass transit is readily available, and the city is wonderfully walkable. And anyone who's been there knows how fast New Yorkers walk and talk. It's that "New York minute" phenomenon. It serves them well.