Twins live longer ‘because close relationships are good for us’

Twins live longer than the general population, according to an analysis of almost 3,000 pairs of twins published in the journal PLOS ONE.

Identical twins had the biggest advantage, researchers at the University of Washington found. The reason, they suggested, was the social support that came with having a twin.

The study looked at Danish twins born between 1870 and 1900 who all survived past the age of 10, using data from the Danish Twin Registry.

Lead author David Sharrow, a postdoctoral researcher in aquatic and fishery sciences at the University of Washington, said: ‘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.’

The strongest benefit for male twins came in their mid-40s, when they had a six percentage point advantage over non-twins. That is, if 84 out of 100 men were still alive aged 45, then for twins that number would be 90. For women the benefit was highest when they were in their 60s. The difference was 10 percentage points.

‘Our results lend support to a big body of literature that shows that social relationships are beneficial to health outcomes,’ said Sharrow.

The study separated acute causes of death (ie, accidental or behaviour-related deaths) from deaths of natural causes. Female twins only had lower mortality for the first category. Male twins had a longevity advantage for both causes of death.

Sharrow suggested the difference was down to the cumulative effect of male twins making healthier choices thanks to the support of a significant other.

‘Males may partake in more risky behaviours, 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 behaviours,’ he said.

Instant analysis
This interesting population-based study suggests there appears to be a survival advantage to being a twin.

Specifically it found that monozygotic twins (twins that result from a single egg, fertilised by a single sperm with the subsequent cell mass splitting off into two and are hence identical) live longer than dizygotic twins (twins resulting from two eggs being fertilised and are hence non-identical) who, in turn, live longer than individuals who are not twins.

Any population-based study usually establishes correlation and not causation, and in this case we have no direct data to support why being a twin appears to be advantageous. It is possible that the close bond between twins manifests itself in health habits that are perpetuated due to the mutual support available, in the manner of gym partners who encourage each other through arduous workouts. There may be a genetic basis as well, with twins inheriting hardier genes, manifestly more so in monozygotic twins who genetically can be almost identical. Socioeconomic factors may also play a role, along with many other possible factors.

Whether this study is applicable to more heterogenous populations remains to be seen. Denmark is relatively homogenous — about 90 per cent of the population are of Danish descent — something not necessarily reflected in the ethnic make-up of other European countries.

Take-home message: being a twin may seriously enhance your health. Then again, it may not.
TSA
Research score: 2/5


  • NickG

    Could by a confounding effect, that is that the genetic predisposition that generates twins, which is heritable and will thus be present in twins, has a fitness/ longevity benefit.

    That is that the longevity benefit may be genetically determined and heritable rather than as a secondary effect of and benefit of the social interaction involved in being twins.

    Many studies on behaviour and environment, and much health and parenting advice miss this basic fundamental that correlation does not equal causation matter.

  • Spencer

    I think the scientists are missing one basic incredibly obvious fact. Parents of boy twins whether fraternal or identical spend the first few years of their lives frantically trying to restrain their daredevil behaviour as toddlers (when one parent is in charge) and therefore spell out the dangers in a more explicit way. This doesn’t restrain their behaviour as they move out of the toddler stage and doesn’t decrease their appetite for danger however twin parents are naturally always telling twins how to balance risk and assess it, not that this always works. Anecdotally I would also say that twin boy parents encourage controlled risky behaviour much more than other parents if only to try and expend the boundless energy that they have. Although I do believe the mutual support system for male fraternal twins is more important in teenage years.

  • Jeff

    Gated Communities

    Gated communities are taking on an important role in modern politics. Donald Trump grew up in a gated community, and made his fortune building gated communities that illegally exclude African-Americans. Trump’s approach is not based on ideology, but on consumer demand, and in particular, the demand of the working class to live in a place where there are no minority groups, criminals, wierdos or politically correct (Catholic educated) people.

    A gated community has a number of characteristics. There is ideally a six metre high concrete wall to keep out intruders. When the wall surrounds a very large number of houses, the average cost of the wall becomes insignificant. Getting past the security guards is like going through customs. Hence there is no crime in a gated community, and children can roam unsupervised in complete safety. Parents can be sure their daughters will not encounter males that would be unsuitable sons-in-law.

    Allotments are typically quarter-acre or five acres (one-tenth or two hectares). Houses are fireproof and of a similar appearance. Services are provided by underground ducts, including pneumatic mail delivery. Television and internet are unobtrusively censored.

    There is a shopping centre with a supermarket and other key shops. Prices are controlled to prevent gouging. There is a club for men and older boys from which women are excluded. On the top of the shopping centre is a hospital and old people’s home overlooking a race track and playing fields.

    There is a non-denomination church, which has leather sofas instead of pews, and wallpaper with pictures of saints like in an eastern orthodox church. The priest is a family man employed by the management committee. There is a co-educational school, so that if children conceive a passionate desire for a classmate, it will be someone of the opposite gender. The school has international baccalaureate and no homework.

    Once people move into a gated community, it occurs to them that, instead of their having to move into a gated community, it would be better if the “undesirables” were forced to live in ghettos, or were kicked out of the country altogether. No doubt this is what Donald Trump has in mind. The Conservative Party should take on board this trend in modern living and become the party for people who live or would like to live in gated communities. es