Anna Lisovskaya/Shutterstock
Source: Anna Lisovskaya/Shutterstock

A new study analyzed data from one of the oldest and most complete registries of information about twins in the world—2,932 pairs of same-sex twins born in Denmark between 1870 and 1900—and compared their lifespans to that of the general population.

The authors found that at nearly every age, identical twins survived longer than fraternal twins, who, in turn, had greater longevity than the general population.

Why do twins live longer? 

We already know that a similar longevity effect has been found for marriage: Married people tend to be healthier than unmarried people and live longer. However, drawing clear conclusions from marriage data is complicated because it is unclear whether marriage itself makes people healthier or whether healthier people choose to get and stay married. Because twins have no choice about their twinhood, it is easier to tease out the contributing factors to their longevity.

The researchers concluded twins’ greater longevity results from three factors:

  1. 1Twins are more likely to provide each other emotional and other kinds of support during difficult and stressful times. Because identical twins are more similar than fraternal twins, they might be better at knowing when their twin needs support and how to provide it, which explains the small advantage in longevity identical twins have over fraternal twins.
     
  2. The close, life-long relationship twins have might buffer them from risky behaviors because they have someone looking out for their best interests. The researchers concluded this is especially true for male twins, because men are more prone to risky behaviors than women.
     
  3. The mutual care twins often exhibit can prevent risky decisions and behaviors, and promote healthy ones. Twins may inspire one another to adopt healthy habits. They might also benefit from seeing their counterpart succeed at healthy endeavors, making them feel more assured of success if they set similar goals.  

Full disclosure: I am an identical twin and have an extremely supportive relationship with my brother. However, the findings of this study demonstrate the importance of close, life-long social bonds of any kind. True, twins have the advantage of built-in social and emotional support, but similar benefits can also be derived from having a life-long best friend, a long and supportive marriage, or an extremely close relationship with anyone we choose to share our lives with. Indeed, having a close circle of friends or a tight-knit community has also been found to increase longevity.

Therefore, what this study actually illustrates is the importance of maintaining close and highly supportive relationships. They not only enrich our lives, they also extend them.