In a study of twins, 95 per cent of the link between intelligence and lifespan was genetic, with smarter siblings outliving their “dumber” counterparts.
And the effect was more in non-identical twins than in identical twins who share more of the same DNA. But researchers reassured parents a child’s exams results was not an indication of their lifespan as the link was “small”.
Research associate Rosalind Arden at the London School of Economics and Political Science said: “We know that children who score higher in IQ-type tests are prone to living longer.
“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.
“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.
“However, it’s important to emphasise that the association between intelligence and lifespan is small.
“So you can’t, for example, deduce your child’s likely lifespan from how he or she does in their exams this summer. It could be that people whose genes make them brighter also have genes for a healthy body.
“Or intelligence and lifespan may both be sensitive to overall mutations, with people with fewer genetic mutations being more intelligent and living longer.
“We need to continue to test these ideas to understand what processes are in play.”
Studies that compare genetically identical twins with fraternal twins who only share half of their twins DNA, help distinguish the effects of genes from the effects of shared environmental factors such as housing, schooling and childhood nutrition.
The study, published in the International Journal of Epidemiology, looked at three different twin studies from Sweden, the United States and Denmark where both intelligence and age of death was recorded and where at least one twin in each pair had died.
Only twins of the same sex were included in the analysis.Another recent study found that people with demanding jobs can live up to three years longer after being affected by a common form of dementia.
The longer survival may be due to having greater mental reserves which provide them with an effective buffer against the condition, it is claimed.
Doctors have long held that keeping your brain active – especially in later years – could be the best insurance against developing Alzheimer’s and other forms of dementia.
The new study found that people with frontotemporal dementia – which results in changes in personality or behaviour and problems with language, but does not affect memory –lived for longer if they had a more intellectually demanding occupation.
Dr Lauren Massimo, of Pennsylvania State University, said: “This study suggests that having a higher occupational level protects the brain from some of the effects of this disease, allowing people to live longer after developing the disease.”