Analyzing data from a five-year study, Stephanie Brown, a psychologist at the University of Michigan Ann Arbor, examined social support in elderly folks.
Under scrutiny was practical support--such as help with the daily chores--as well as emotional support, such as listening to your spouse's troubles. The relative presence, or absence, of these things was correlated with survival rates.
Her findings are surprising. Her study didn't find that people who received support lived any longer on average. Instead, it found that people who gave the support were living longer. The health benefits were reaped by the care-givers more than the care-receivers!
Older folks in the study who were either practical help- givers to neighbors and friends, or emotional support-givers to their spouses, had as little as half the death rate of people who were the receivers of help. Receivers, on the other hand, lived on average no longer than other folks.
Of course, part of the effect may be that help-givers are just stronger in the first place. But beyond this, there does seem to be something life-giving about helping other people with their lives.