They might send your stress levels through the roof – but the key to living a long life is having more children, study says

People who have children are more likely to live to 76 – with two offspring appearing most beneficial, a new study suggests.

Researchers from the University of Michigan examined the genetic and health information of 276,000 people in Britain.

They found that genetic variants associated with higher reproduction have become increasingly common in recent decades.

And they found that having children seemed to be linked to a greater chance of surviving into old age.

Professor Jianzhi Zhang, one of the study's authors, said: 'One thing is relatively clear: having children is more beneficial for longevity than having no children at all.

'What we measured was the probability of living to the age of 76.

'Those with children have a 5 to 10 percent advantage over those without children.

'Interestingly, we found that… having two children corresponds to the longest life span. Having fewer or more children shortens lifespan.'

Although their study did not explore the possible reasons for this, Professor Zhang said other research has suggested a link between having children and social contact.

“Previous studies have shown that people with children tend to have more social interactions, such as interactions with other parents and teachers, and it is known that more social contact is associated with a longer life,” he added.

“It's possible that having two children strikes a balance between having a good amount of social interactions and not having too many economic or physical burdens.”

Surprisingly, the research also seemed to suggest that the genetic mutations linked to reproduction – which make people more fertile – were also linked to a shorter lifespan.

This supports a decades-old theory of evolution, first proposed by biologist George Williams in 1957, that genetic mutations that contribute to aging could be favored by natural selection – and passed down from generation to generation – if they are beneficial earlier in life in promoting earlier reproduction or the production of more offspring.

However, the researchers – whose findings have been published in the journal Science Advances – said that both the ability to have children and lifespan are influenced by both genes and the environment.

And compared to environmental factors – such as the impact of contraception and abortion on reproduction, and medical advances on longevity – genetic factors actually play a relatively small role.

A previous study found that women who have had multiple children may have a lower risk of dementia.

Experts have found that higher estrogen exposure throughout a woman's life can lead to a healthier brain.

Those with a longer 'reproductive lifespan', or who have had multiple children, accumulate higher exposure to the hormone.

And this appears to lead to a lower risk of cerebral small vessel disease – a condition that results from damage to small blood vessels in the brain and is linked to cognitive impairment and dementia.