One out of every 150 children born in the United States has autism or a closely related disorder, according to the Centers for Disease Control and Prevention. The cause is mysterious, and the only way to diagnose the condition is by observing the behavioral symptoms, such as trouble with language, lack of eye contact, or social isolation.
Much autism research focuses on identifying risk factors and facilitating early diagnosis to allow more effective interventions that will improve language and social skills.
In the 1990s, Karl Kuban, a School of Medicine professor of pediatrics and neurology and chief of pediatric neurology at Boston Medical Center (BMC), observed something that could help identify one of those risk factors: a high rate of autism among children who had participated as infants in an earlier study of premature birth.
To determine whether premature birth was associated with an increased autism risk, Kuban and fellow researchers from MED and BMC teamed up with scientists in other medical centers on a study led by Alan Leviton, director of neuroepidemiology at Children’s Hospital Boston.
Beginning in 2004, the researchers, working in 11 cities across 5 states, gave a standard autism screening to nearly 1,000 two-year-olds who had been born more than 12 weeks premature. The screening, known as M-CHAT, measures an infant’s ability to play and communicate with a caregiver.
What was found
While 5.7 percent of children in the general population evaluated with M-CHAT score positive for increased risk of developing autism, more than 21 percent of the study subjects screened positive. “It was pretty eye-popping for us,” says Kuban.
The researchers recognized that the prematurely born children in their study also had much higher rates of visual, hearing, and motor impairments, which have nothing to do with autism, but could lead to a false positive result on the screen. But after removing these cases from their analysis, they ended up with 16 percent scoring positive on the M-CHAT evaluation, nearly triple the normal percentage. And even when they also left out children who had cerebral palsy or other measurable cognitive impairments, the children in the study still screened positive at an elevated rate of about 10 percent.
Their findings appear in the January issue of the Journal of Pediatrics.
Why it matters
Kuban says that if follow-up studies of these children confirm an association between premature birth and autism, it will “open up avenues of research that may help us understand what contributes to autism risk.” It could also help clinicians diagnose autism at an earlier age, thereby increasing the effectiveness of interventions.
Word to the wise
The researchers note that M-CHAT is a screen for autism, not a predictor of the disorder. In fact, according to Kuban, the positive rate for the screening is 10 times the rate of autism. “There are many children who can screen positive and don’t end up with autism or any kind of disability,” he says.
Kuban also emphasizes that the study does not show a causative link between premature birth and autism. “It would be a mistake to think that because a baby is born very early, it causes this disorder,” he says. “We think there are some common risks associated with both premature birth and autism, and not that one causes the other.”
The researchers are applying for funding from the National Institutes of Health to continue following this cohort of children to see what percentage of them are, in fact, diagnosed with autism.
Submitted by Chris Berdik for BU Today.