FRIDAY, Jan. 11 (HealthDay News) -- Here's yet another reason to get hitched and stay hitched: New research suggests that being single during midlife appears to raise the risk for premature death.

The finding applies specifically to American men and women who've already entered their 40s, when the likelihood for continuing to live to a ripe old age is high. However, investigators say, marital status appears to significantly affect the odds, with those entering midlife single facing more than twice the risk of dying early than those who are part of a permanent partnership.

Study author Ilene Siegler, a professor of medical psychology with the department of psychiatry and behavioral sciences at Duke University Medical Center, reports her team's research online Jan. 10 in the Annals of Behavioral Medicine.

The authors noted that Americans who reach the age of 40 can look forward to an average overall life expectancy of roughly 83 years.

That said, the team set out to assess how marital status might impact this figure by analyzing data collected by the UNC Alumni Heart Study, which included more than 4,800 men and women (82 percent men, and all white), all of whom had been born during the 1940s.

The study had been designed to look at how personality traits evident during one's college years (in this case between 1964 and 1966) might ultimately affect the risk for developing coronary heart disease down the road. Such traits included optimism, pessimism, depression, sociability and hostility.

The influence of other behavioral factors (such as educational and professional attainments, smoking and alcohol histories and exercise habits) were also weighed, alongside changing marital status and death incidence.

The results: compared with currently married men and women, individuals who entered midlife without ever having been married were found to face more than double the risk for death during midlife.

Similarly, those who had previously been married but were no longer married when entering midlife were also found to face a relatively elevated risk for death (1.64 times the risk of married individuals).

The researchers said the findings held constant even after accounting for all the personality, behavioral and health-related risk factors that might theoretically affect death risk.

They suggested that "chronic loneliness" could be one key element, among others, driving the mortality boost, a phenomenon they said it will be increasingly important to get a handle on as the population ages.

While Markie Blumer, an assistant professor with the marriage and family therapy program at the University of Nevada, Las Vegas, said the research is "solid," she cautioned against "putting all our eggs in the basket of marriage."

"As a clinician, this helps me realize that when I'm working with baby boomers, as couples or as individuals, I need to make sure they have good social support," she noted. "At the same time, this study has many limitations, some of which the authors acknowledge, and all of which are important to consider when you are sending out the message that you need to rely on your spouse for your health, or that that's where your health comes from. Because for people who are single or had a partner who's since died I think that message can be very dangerous."

Blumer pointed to the lack of ethnic and socioeconomic diversity in the study sample; the lack of consideration given to parental history in terms of marriage; the insufficient discussion of the role of cohabitation outside of marriage; or the critical role played by friends and children in terms of providing non-spousal social support. And she described the study's male-centric focus as particularly "problematic," given that "other studies show that while married men live longer and are happier, married women do not. So, women need to read about this research with a mindful eye."

On that point, Janice Kiecolt-Glaser, chair of medicine and a professor of psychiatry and psychology at the Institute for Behavioral Medicine Research at Ohio State University, confirmed that gender differences when it comes to marriage's effect on health are "sizeable."

"The reasons appear to be related to women's larger social networks," she said. "Women are more likely than men to have a large and diverse group of friends and relatives with whom they share and feel close to. For men, the wife is typically the primary person who serves as a confidant, so that it is often true that a man without a partner has no confidant."

The association seen between marriage and survival in this study does not prove a cause-and-effect relationship.

More information

For more on life expectancy, visit the U.S. Centers for Disease Control and Prevention.