Autism Tied to Older Fathers

Men over 40 are nearly six times as likely to have an autistic child as those under 30, according to a new study that provides support for the role of genetics in the development of the disabling mental disorder.

At least two previous small studies have hinted at such a link, said epidemiologist Abraham Reichenberg of the Mt. Sinai School of Medicine, who led the new study.

His team examined records of more than 318,000 Israelis born in the 1980s, providing "the first convincing evidence" that advancing paternal age is an important risk factor for development of the disorder, he said.

In a surprising discovery, the team also found that the gender ratio of the afflicted children changes as the father ages. Typically, about six times as many boys as girls develop the disorder. When the fathers are over 40, however, the ratio is 1 to 1.

"That might suggest that there are different mechanisms contributing to autism in males than in females, or that the mechanism changes for older fathers," Reichenberg said.

Like earlier studies, the new one, reported Monday in the Archives of General Psychiatry, found no significant effect associated with older mothers.

Autism is a severe developmental disorder in which children seem isolated from the world. There is a broad spectrum of symptoms, marked by poor language skills and an inability to handle social relations. No cure exists, but many problems can be alleviated with intensive behavioral therapy.

A recent government study found that the disorder strikes about one in every 175 children, up substantially from the incidence of about one in 1,000 observed two decades ago. Although some of the increase is due to better diagnosis of autism, researchers are at a loss to explain the bulk of the increase.

Most researchers now believe that genetics plays a role in the onset of autism, said Dr. Fred Volkmar of Yale University, who was not involved in the study. So far, however, it has not been possible to implicate specific genes. Reichenberg's results could provide useful clues, he noted.

A growing number of congenital disorders have already been linked to older fathers, including Apert syndrome, syndactyly, cleft lip and decreased intellectual capacity. Reichenberg's group also recently identified a higher risk of schizophrenia among offspring of older men.