Gay men who are in same-sex marriages are living longer, according to a new study that looked at the Danish population.
"Our study expands on century-old knowledge that married people generally have lower mortality than unmarried and divorced persons," lead author Dr. Morten Frisch, a professor of epidemiology at Aalborg University, wrote according to the Los Angeles Times. "From a public health viewpoint it is important to try and identify those underlying factors and mechanisms."
The study, which was published Mar. 11 in the International Journal of Epidemiology, looked at the mortality -- or death -- rates of 6.5 million Danish adults from 1982 to 2011 who were in relationships during that time. The rates of mortality for married gay men has been going down since 1996, and now is lower than that of unmarried or divorced heterosexual men.
"Among men in Denmark, it is more dangerous to be unmarried or divorced than to be married to another man," Frisch told Live Science in a separate interview.
Denmark was the first country to allow same-sex partnerships in 1989. Researchers used information from the Civil Registration System, which gives out identification numbers similar to Social Security numbers in the U.S.
Out of the 6.5 million people who the researchers had marital information on, 1.7 million died during the study period. Homosexual couples made up less than 1 percent of the study sample, so researchers cautioned that their findings may not be as representative of the population.
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Men and women in heterosexual marriages had the lowest rate of mortality, which researchers think may be attributed to income, health care, social support and other similar factors. But, divorce may take a toll on health: Mortality rates rose 27 percent for each additional marriage after their first for women and 16 percent for men.
For heterosexuals, male widowers were 1.4 times more likely to die than married straight men by 2011, up from 1.2 times in 1982. Divorced men went from 1.3 to 1.7 times more likely to die than their married counterparts in the same time frame. Unmarried men went from 1.2 times more likely to die in 1982 to 1.7 in 2011.
Gay men who were married were only 1.4 times more likely to die by 2011, making their rates of dying lower than those of heterosexual divorced or unmarried men. Scientists believed that improvements in therapies for HIV and AIDS have helped lower mortality rates.
Straight female widows were 1.4 times more likely to pass away during the period than those who were married to a man. Divorcees were 1.6 times more likely to die than their heterosexual married counterparts during the study's time frame. Unmarried women were 1.7 times more likely to die than married women in 2012, up from 1.5 times in 1982 when the study started.
Unlike the men, mortality rates have increased slightly for married lesbian couples, with rates higher than those of married gay men and heterosexual couples who live together. Researchers believe that it is because married lesbians were 60 percent more likely to die from cancer and six times more likely to commit suicide than married straight women, although the reasons why are unknown.
"Since the year 2000, same-sex married Danish lesbians have had mortality rates that are almost 90 percent higher than opposite-sex women in Denmark," he said to Live Science.
Suicide rates for same sex male couples were also higher than those for married straight couples.
"It is important now to identify those factors that make more homosexuals than heterosexuals vulnerable to life's challenges to such an extent that suicide may appear to be the only way out," Frisch said.