Twins live longer than other people, and their close social connection may be a major reason why, a new study says.

Researchers reviewed data from more than 2,900 same-sex twins. They were born in Denmark between 1870 and 1900. The study only included data from twins who lived past age 10. The researchers compared the twins to the general Danish population.

At every age, identical twins had higher survival rates than fraternal twins. And, fraternal twins had higher survival rates than people in the general population.

For men, the peak survival benefit of being a twin was at age 45. Male twins' survival rate at that age was 90 percent, compared with 84 percent in the general population. For women, the peak survival benefit of being a twin occurred in their early 60s. About 10 percent more female twins made it to their early 60s than in the general population.

The findings, published recently in the journal PLoS One, reflect the health benefits of the close social ties between twins.

"There is benefit to having someone who is socially close to you who is looking out for you. They may provide material or emotional support that lead to better longevity outcomes," study author David Sharrow, a postdoctoral researcher at the University of Washington, said in a university news release.

For example, a close companion can discourage bad habits and encourage healthy behaviors, act as a caregiver during an illness, and provide emotional support.

If the findings are confirmed in other sets of data, they would have implications beyond twins.

"Research shows that these kinds of social interactions, or social bonds, are important in lots of settings," Sharrow said. "Most people may not have a twin, but as a society we may choose to invest in social bonds as a way to promote health and longevity."