OLDER DADS PAST 33 THE RISKS RISE WITH INCREASING PATERNAL AGE

The link between schizophrenia and older paternity had been made before, but this was the first large study to look at a range of factors that could confound the results, said Professor John McGrath, a psychiatric epidemiologist at the Queensland Centre for Mental Health Research.

"If all babies had fathers less than 30, the paper suggests, the incidence of schizophrenia would reduce by 15 per cent," he said.

In 2002 the average age of fathers was 32, compared with an average age of 29 in 1982, according to data from the Australian Bureau of Statistics.

The executive director of the mental health lobby group SANE Australia, Barbara Hocking, said the Swedish research, published in the British medical journal BMJ, was "major, major stuff".

She likened the research to the link between mothers over 35 and an increased risk of Down syndrome in their children. "It helps people understand what risk factors may be, so you can take action to reduce them."




Obstetrics & Gynecology 1981;57:745-749
© 1981 by The American College of Obstetricians and Gynecologists


Genetic disease in the offspring of older fathers
JM Friedman


Autosomal dominant genetic diseases may result from the transmission of a trait by a carrier parent or from gene mutation in one of the gametes from which the child develops. The mean age of fathers of affected persons has been found to be greater than expected for several autosomal dominant diseases due to new mutations. To assess the clinical importance of this observation, the relative and absolute frequencies of offspring with autosomal dominant diseases due to mutation in the sperm from fathers of various ages have been calculated. The relative frequency of new autosomal dominant mutations in children increases logarithmically with paternal age during the usual years of fatherhood. The absolute frequency of autosomal dominant disease due to new mutations among the offspring of fathers who are 40 years of age or older is estimated to be at least 0.3 to 0.5%. This risk is many times greater than that for children of young fathers and is similar in magnitude to the risk of Down syndrome among the offspring of 35- to 40-year-old mothers. Thus, it is good public health policy to recommend that both men and women complete their family a before age 40, if possible.




Combined Effect of Older Mothers and Fathers Increases Baby's Risk
By Jennifer Warner
WebMD Medical NewsReviewed by Brunilda Nazario, MDJuly 1, 2003 -- Older fathers may contribute just as much as older mothers to the dramatic increase in Down syndrome risk faced by babies born to older couples. A new study found that older fathers were responsible for up to 50% of the rise in Down syndrome risk when the mother was also over 40.

Researchers say the number of births to parents over age 35 has more than doubled in the last 20 years and this has raised questions about the role of paternal age in the risk of genetic abnormalities and birth defects.

Previous studies have shown that the risk of a woman having a baby with Down syndrome rises dramatically after she reaches 35. Although this effect of maternal age on Down syndrome risk is well known, researchers say the influence of the father's age on Down syndrome has not yet been defined. Some studies have found no relationship, while other, smaller studies have suggested that older fathers may raise the risk of Down syndrome.

But researchers say this study, published in The Journal of Urology, is the largest of its kind and looked at 3,429 Down syndrome cases reported to the New York State Department of Health from 1983 to 1997. Their findings suggest that the increase in the number of babies with the genetic abnormality born to women over 35 may be the result of a combined effect of both advanced maternal and paternal ages.

Older Fathers Face More Risks
The study showed that the percentage of births to women over 35 grew from 8% of all births in 1983 to 17% in 1997, and the greatest change during this period was the number of births to mothers and fathers over 40 years old, which rose by 178% and 73%, respectively.

Researchers found that the rate of Down syndrome among parents over 40 was 60 per 10,000 births, which is six times higher than the rate found among couples under 35 years old. Older fathers over 40 had twice the rate of Down syndrome births compared with men 24 years old and younger when they had children with women over 35.

"Paternal age has an effect on Down syndrome but only in mothers 35 years old and older," write researcher Harry Fisch, MD, of the department of urology at Columbia-Presbyterian Medical Center in New York City, and colleagues. "In younger women, in whom age was not a risk factor for Down syndrome, there was no paternal effect."

Among older mothers over 40, researchers found that an increase of 50% in Down syndrome risk was attributable to the advanced age of the father.

In fact, researchers suggest that there is only a modest increase in Down syndrome risk for women 35-39 compared with women 30-35 years old, but the dramatic increase in Down syndrome births among women 35 to 39 years old is largely due to the influence of older fathers because older women tend to make babies with older men.