First-time fathers' age and schizophrenia risk
Men who are relatively older at their first child's birth may be more likely than younger first-time fathers to have a child who eventually develops schizophrenia.
It's known that schizophrenia is a disorder of disrupted brain development, and it has been long believed that it arises from a combination of genetic susceptibility and environmental factors - with the suspects including viral infections or poor nutrition during pregnancy. Previous studies have also shown a relationship between parents' age at the time of a child's birth and that child's risk of developing schizophrenia.
Researchers analysed data on 2.2 million people born in Denmark between 1955 and 1992, and found a link between first-time fathers' age and the odds of any of their children developing schizophrenia. In contrast, the connection was not seen among fathers who were relatively older only when their second- or later-born child came into the world. Between 1970 and 2007, just over 14,200 of those individuals were diagnosed with schizophrenia. Among fathers who were between the ages of 25 and 29 when their oldest child was born, there were 2,420 cases of schizophrenia among their 448,538 children - a rate of about 0.5 percent. The corresponding rate was 0.7 percent among fathers who were in their 30s when their first child was born, just under 1.2 percent for fathers in their 40s, and 2 percent for those age 50 or older at the birth of their first child. Family history of mental illness did not explain the connection between first-time fathers' age and their children's odds of developing the disorder.
Researchers have speculated that the explanation might rest in the fact that older fathers are more likely than younger ones to have genetic abnormalities in their sperm, possibly including genetic abnormalities related to schizophrenia.
However, the new findings cast doubt on that theory. If the theory were correct, then fathers' age at the birth of any child - not just the first one - should be related to schizophrenia risk. Instead, the findings support another theory - that men who have a predisposition to schizophrenia, but do not themselves develop it, tend to have children later in life than other men.
Another possibility is that men predisposed to schizophrenia are more likely to have personality traits that affect their relationships and make it more difficult to find a partner. The vast majority of children born to relatively older fathers will not develop schizophrenia, as the disorder is estimated to affect 1 percent of the population. However, a better understanding of the relationship between paternal age and schizophrenia risk could help uncover some of the causes of the disorder.
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