Comparing siblings, scientists establish a link between the father's age and children's mental health and school presentation.
Children born to fathers over the age of 45 are at higher side of risk of developing psychiatric problems and more possible to struggle at school, according to the research of a large-scale study.
The research originate that children with older fathers were more frequently diagnosed with disorders such as psychosis, autism, attention deficit hyperactivity disorder (ADHD), bipolar disorder and schizophrenia. They also reported more drug addiction and suicide attempts, researchers said.
The children's problems seemed to distress school performance, leading to poorer grades at the age of 15 and fewer years in education on the whole.
"We were surprised when we saw the comparisons," said Brian D'Onofrio, the first writer of the study at Indiana University in the USA. But he added that it was not possible to be sure that older age was to responsibility for the problems.
Scientists have found links between fathers' age and children's cognitive presentation and health before but this study recommends the risks may be more severe than previously thought. The increased risks might be caused by genetic mutations that build up in sperm as men age.
Researchers at the Indiana University and the Karolinska Institute in Stockholm studied medical and educational records of much more than 2.6 million babies born to 1.4 million men. The group amounted to almost 90% of births in Sweden from 1973 and 2001. Using the records, the scientists added up diagnoses for psychiatric disorders and educational success and compared the numbers for children born to fathers of different ages.
The figures told a multifaceted story. When health and school presentation were compared across all the children, and factors such as parents' education and any history of psychiatric illness were taken into relation, paternal age made small difference, except for cases of bipolar disorder, which increases with older fathers.
But the researchers went on to do one more analysis. This evaluates the health and presentation of siblings in the same families, in the hope of ruling out dissimilarity between families that may have twisted the results. This time they found an outstanding link between paternal age and children's mental health and educational results.
According to the study, the children of fathers aged 45 and over were 3.5 times as expected to have autism, had more than two times the risk of psychotic disorders, suicidal activities and drug abuse, and had a 13-fold greater risk of ADHD. Less than 1% of children born to younger fathers than 45 had bipolar disorder, a figure that rose to regarding 14% in their siblings when fathers were 45 or older. In most of the cases, the risk of each disorder rose steadily with the father's age.
The impact on educational success was less dramatic. Children with older fathers had a 60% higher risk of poor performance at age 15, defined as the equivalent of an overall fail grade across 16 academic subjects. They were also 70% more likely to spend less than 10 years in formal education.
The findings come into view in the journal JAMA Psychiatry.
Some specialists have questioned the analysis, because significant factors that could be to blame were not ruled out.
While looking at siblings has the benefit of ruling out dissimilarities from one family to the next – such as the number of books on shelves and diet – teasing out cause and effect is not possible.
For example, a first born child may be superior to his/her siblings at school, but that could be down to the parents having more time to use with him or her than later children. The father being younger at his or her birth may be irrelevant. Equally, a man's second wife may be a bad parent than his first wife, with knock-on effects for his children with her. Again, his older age would not be the direct offender.
In a lot of countries, the age of first-time fathers is on the rise, and if the most up-to-date findings are right, that could drive more psychiatric and educational troubles in future generations. The common age of men who became fathers in England and Wales rose from 30.8 to 32.6 years old in the two decades to 2011, with mothers' age rising to 29.7 years old over the same period. In 2011, 31,643 babies were born to fathers aged 45 and over. Various 833 fathers were 60 and over, according to the Office of National Statistics.
Ryan Edwards, who studies the finances of health and ageing at the City University of New York, said the study exposed "some facts that paternal age may worsen children's psychiatric, behavioral and educational results."
But he caution that the results hinged on the scientists' assessment between siblings. "In that setting, it is difficult to divide the overlapping effects of paternal age, children's age, and birth order in a believable way," he said.
Jennifer Roff, also at the City University of New York, had alike reservations. "I'm not saying that there is no probable genetic role for paternal age. I simply think that this could be confused with other environmental factors like birth order. The level of the problem will differ. I can visualize that for things like cognitive scores, this could be a bigger problem than for things like schizophrenia."
