Results of new study provide more evidence that participating in volunteer activities may add years to an older person's life.

In a study of U.S. retirees, researchers found that volunteering significantly reduced the chances of dying over a four-year period.

Volunteering, the investigators say, may improve health outcomes by expanding retirees' social networks, increasing their access to resources and improving their sense of self-worth.

In the study, Dr. Sei J. Lee and colleagues form the VA Medical Center and University of California, San Francisco, examined 6,360 retirees older than age 65 who enrolled the Health and Retirement Study in 2002.

As part of the study, the men and women, whose average age was 78 years, were asked: "Have you spent any time in the past 12 months doing volunteer work for religious, educational, health-related, or other charitable organization?"

Lee and colleagues found that volunteering was strongly associated with lower death rates, with 12 percent of 1,766 volunteers dying by 2006 compared to 26 percent of 4,594 non-volunteers.

Even after adjusting for numerous factors that could influence the results, such as the seniors' socioeconomic status, chronic illnesses, and functional limitations, volunteering remained strongly correlated with lower death rates.

The findings of the study were reported over the weekend at the American Geriatrics Society annual meeting in Chicago.