For the first time, a study has shown that more intelligent people live longer, and the reason is mainly their genes. Researchers from the London School of Economics and Political Science (LSE) studied data from twins, and found that 95 percent of the link between intelligence and lifespan is genetic.

The study showed that among sets of twins, the smarter twin tended to live longer than the less intelligent of the pair. The trait was more pronounced in non-identical twins (fraternal) than in identical twins.

"We know that children who score higher in IQ-type tests are prone to living longer," said Rosalind Arden, a research associate at LSE. "Also, people at the top of an employment hierarchy, such as senior civil servants, tend to be long-lived. But, in both cases, we have not understood why.

"Our research shows that the link between intelligence and longer life is mostly genetic," Arden said. "So, to the extent that being smarter plays a role in doing a top job, the association between top jobs and longer lifespans is more a result of genes than having a big desk."

The researchers analyzed three different twin studies from Sweden, the United States, and Denmark, using only twins of the same sex. All studies recorded both the intelligence and age of death, and at least one twin in each pair had died.

Arden said one of the reasons the smarter twin may live longer is that those who have genes that make them smarter also make them healthier. Or intelligence and lifespan may both be sensitive to gene mutations, and people with fewer mutations are more intelligent and live longer.

In every population studied, people who scored higher on intelligence tests lived longer. A 2001 study found that the higher people scored on IQ tests when they were children, the more likely they were to live to celebrate their 76th birthdays. Another study of Nobel Prize winners found they lived longer than those who were runners-up for the prize.

"It's important to emphasize that the association between intelligence and lifespan is small," Arden said. "So you can't, for example, deduce your child's likely lifespan from how he or she does in their exams this summer."

The researched was published in the International Journal of Epidemiology.