Study finds children from older dads, on average, go on to have fewer children

A research conducted at Georg August University in Gottingen, Germany found that older fathers could affect their child’s fertility later, though this effect was not found in children with older mothers.

While women are born with all the eggs they will ever have, male sperm production goes on throughout a man's life.

However as the cells that create sperm keep dividing, errors starting creeping into the DNA. And while most errors have no effect, some affect the child’s ability to have their own offspring.

On an average, humans have around 60 such mutations each which are not present in either parent.

The study embarked to test the theory that the father's parental age was linked to reduced fertility and survival in children.

They looked at computerised family records in Sweden, Canada and Germany which helped them track the age of children's fathers at the time of their birth.

They then looked to see if the children survived to reproduce themselves, and how many offspring they had, if any.

Of the 1.4 million people included in the study, three of the populations were 'pre-industrial' i.e. living between 1670-1850.

This was to make sure that the effects were not caused by some feature of the modern world, such as plastics or chemicals.

The fourth population was that of modern Swedes born after 1932.

The researchers found that the children of older fathers were less fertile in all the different age groups.

The researchers said their results ruled out other theories such as the age of the mother being the contributing factor, as well as the possibility that older parents were more likely to die while the child was growing up.

Adding that their findings will help in predicting the effect of the increase in older parents in today’s society and how it will affect their children’s survival and reproductive success.  

Most studies into the genetic effect of having an older father have focused on medical and psychiatric problems, as well as intelligence.

For example, among negative effects, older fathers have been found to be more likely to have children with schizophrenia.