The Feel-Good Reason Twins Outlive Everybody Else

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Identical twins are basically superheroes: They look identical, making the ol’ switcheroo an option for spicing up dates or business meetings; they have super-similar childhoods, so it has to be easier for figuring out the ways that your parents messed you up; and according to new research, they live longer than just about everybody else, too.

For a study in PLOS One, University of Washington researchers David J. Sharrow and James J. Anderson dug into one of the oldest data sets on twins, the Danish Twin Registry, which tracked twins born in Denmark between 1870 and 1900. (While that’s a quite a while ago, the timing means that the data on deaths is quite final.) After taking out the twins that died young or moved away, there were 2103 identical pairs and 3760 fraternal pairs. The data set also included whether people died of extrinsic (as in getting killed in a war, or by a car crash or an illness) or intrinsic (long-term health failure) factors. The researchers found that on average, female twins outlived the general population, with the identicals doing better than the fraternals. Male twins also had higher survival rates than the general population, and again the identicals also outlived the fraternals.

There’s something super interesting (and traditionalist) in the data on guys: Sharrow and Anderson found that the survival advantage for identical male twins is “driven by lower extrinsic mortality in midlife and lower intrinsic mortality in old age” compared to fraternal male twins and the rest of the population. Essentially, having a twin insulates bros from classically masculine stupidity. “Males may partake in more risky behaviors, so men may have more room to benefit from having a protective other — in this case a twin — who can pull them away for those behaviors,” Sharrow said. “There is some evidence that identical twins are actually closer than fraternal twins … If they’re even more similar, they may be better able to predict the needs of their twin and care for them.”

These findings rhyme with the research that’s grown up around what social scientists call “the marriage-protection effect,” where married people tend to live longer (and spot cancer faster) than the unmarried, and the effect is especially strong for men. The reasoning is that a partner will support you in sickness and in health, so that when you lose your job or your parents die you have someone to talk things through with. But at the same time, a selection effect could be at work for protection offered by marriage: Maybe people who get hitched are healthier than the slatternly heathens who choose not to partake in the venerated social ceremony. Since you can’t opt in to being someone’s twin, this study is further evidence that deep relationships literally lengthen people’s lives. When you’re not strong, you need a shoulder to lean on — whether it’s identical to yours or not.