EAST LANSING, Mich. - An international study developed at Michigan State University shows that children who are born weighing less than two pounds exhibit a number of behavioral problems later in life - including hyperactivity and social problems - despite their cultural differences.
The study, published in the May 26 issue of the journal The Lancet, found that behavioral problems among extremely low birthweight (ELBW) children were similar in the four participating countries, thus strengthening the suggestion that such behavior is biological in origin.
"These findings are quite striking," said Nigel S. Paneth, chairperson of MSU's Department of Epidemiology and one of the study's authors. "In spite of language differences and cultural differences, we got pretty much the same picture from each country."
The study looked at more than 400 ELBW children from the United States, Canada, Germany and the Netherlands. The children's parents completed the Child Behavior Checklist, a standard test designed to measure behavioral problems.
Paneth said that two types of behavior problems - internalized behaviors, such as loneliness and anxiety, and externalizing behaviors, such as aggression - were not more frequent in ELBW children than in normal birthweight children. However, a somewhat uncharted middle ground of behavior problems was distinctively more common in the children in all four countries studied.
"What emerges is a profile of a kid who tends to be hyperactive, probably doesn't have too many friends and expresses unusual thoughts," Paneth said. "They're neither sad or depressed nor disruptive."
Extremely low birthweight and behavioral problems have been linked for a number of years, said Paneth. What has changed, he said, is the technology to keep these tiny babies alive.
"It's really a whole new world," he said. "In 1960, approximately 100 to 200 children who were born in the United States weighing two pounds or less survived. By 2000, that number had increased to between 15,000 and 20,000."
Why does this behavioral pattern develop? Theories abound, said Paneth, including brain and other central nervous system injuries that can occur at birth, as well as the extreme circumstances that surround such a birth.
"These babies have very unusual experiences," he said. "They're in incubators; some are on respirators. There is isolation and sensory deprivation. We don't yet know the long-term effects of those experiences."
Other participants in this study were TNO Prevention and Health of the Netherlands; McMaster University of Hamilton, Ont.; the University of Hertfordshire of the United Kingdom; the University of Munich Children's Hospital; Columbia University; and the University of Pennsylvania.
The research was funded by the Agency for Healthcare Research and Quality, a division of the U.S. Department of Health and Human Services.
A copy of the paper is available at http://www.thelancet.com
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