The Wall Street Journal published a recent article (subscription required) discussing findings that were presented at the American Heart Association's annual epidemiology and prevention conference in San Francisco.

According to one presenter, "if you are fit in mid-life you double your chances of living to age 85.  In other words, if you are not fit in your 50s, your projected life-span is 8 years shorter than if you are fit."

The most important factor affecting the longevity of middle-aged people is to be physically fit during that time period.