Why do people in hong kong live so long?

Hong Kong has the longest life expectancy of almost all countries in the world? Men at 78.8 and Women at 84.5 in 2005. While children seem to take care of the elderly, and the elderly are active (doing tai chi in public squares), Hong Kong still doesn't seem to be a very healthy environment with extreme weather, overcrowding, rude pushy people, fatty foods......so what gives?