Having a twin brother or sister increases your chances of living a life longer than singletons, new research has found.
Twins have lower mortality rates for both sexes throughout their lifetimes, the findings showed.
The researchers believe their results reflect the benefits of close social connections that twins generally share.
"We find that at nearly every age, identical twins survive at higher proportions than fraternal twins, and fraternal twins are a little higher than the general population," said lead author David Sharrow from University of Washington.
The data comes from the Danish Twin Registry, one of the oldest repositories of information about twins.
The authors looked at 2,932 pairs of same-sex twins who survived past the age of 10 who were born in Denmark between 1870 and 1900, so all had a complete lifespan.
They then compared their ages at death with data for the overall Danish population.
For men, they found that the peak benefit of having a twin came in the mid-40s.
That difference is about 6 percentage points, meaning that if out of 100 boys in the general population, 84 were still alive at age 45, then for twins that number was 90.
For women, the peak mortality advantage came in their early 60s, and the difference was about 10 percentage points.
"Our results lend support to a big body of literature that shows that social relationships are beneficial to health outcomes," Sharrow said.
A social network can boost health in many ways, he said. Friends can provide healthy outlets and activities, and encourage you to give up bad habits.
Just having a shoulder to cry on, a caregiver during an illness, or a friend to vent with can be healthy over the long term.
"There is benefit to having someone who is socially close to you who is looking out for you," Sharrow said.
"They may provide material or emotional support that lead to better longevity outcomes," he explained.
The study was published in the journal PLOS ONE.
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