SAN DIEGO -- A study by the University of California, San Diego and the University of California, Los Angeles professors found that out of 67,000 Americans, those who never married tended to die earlier than those who were divorced, separated or widowed.

While researchers have long noted that married couples typically live longer than people who are single, the study was the first to distinguish the components of the "unmarried" category, The San Diego Union-Tribune reported.

The researchers tracked census and death certificate data for adults between 1989 and 1997. They determined that divorced or separated people were 27 percent more likely to have died during that time period than married people living together. Widows and widowers were 39 percent more likely, and those who never married were 58 percent more likely, the newspaper reported.

"It's possible that saying, `I do,' will help you live longer," UCSD professor Richard Kronick told the Union-Tribune.

Even divorcees may gain from social relations that might not have formed without matrimony, said Kronick and Robert Kaplan, a UCLA researcher, according to the newspaper.

The study, published in the September edition of the Journal of Epidemiology and Community Health, controlled for education, income and self- reported health status, according to the Union-Tribune.

Kronick and Kaplan said there were other factors, such as married people being less likely to engage in risky behavior, the newspaper reported.

Smokers may choose to quit after marrying, Kronick said, because they have a different sense of their future or a stronger desire to stay alive, according to the researchers.