Premature Infants at Increased Risk for Attention Deficit Disorder
In the United States, more than 500,000 babies are born each year before 37 completed weeks of pregnancy, representing a 36% increase since the early 1980’s. Premature infants are at a greater risk for health complications including breathing problems and developmental delays. Preemies are also at a modestly higher risk of attention deficit-hyperactivity disorder (ADHD) according to research presented by the Karolinska Institute in the May issue of the journal Pediatrics.
Socioeconomic Factors May Contribute to ADHD Risk
Researcher Anders Hjern MD PhD and colleagues used the Swedish Medical Birth Register to evaluate more than one million children born between 1987 and 2000. About 7,500 of them were prescribed ADHD medications between the ages of 6 and 19 according to the Swedish Prescribed Drug Register. Methylphenidate, atomoxetine, and amphetamine were the most commonly purchased ADHD drugs.
After controlling for age, gender and other factors, the researchers found that children born extremely prematurely – between 23 and 28 weeks of pregnancy – had a two and a half times greater risk of later developing ADHD over a child born at full term. Even those children born slightly early (37 to 38 weeks) were at a 20% increased risk of the disorder.
The researchers found essentially the same risk estimates in an analysis controlling for genetic factors by comparing the 34,334 children of women who had given birth to both preterm and term infants.
Low birth-weight and severe prematurity were already known to be risk factors for developing ADHD, but this is the first study to suggest that the risk exists even beyond the extreme cases. "The finding that early term birth carries an increased risk for ADHD has important implications for planned cesarean births, which are often performed during these very weeks," Hjern told Reuters Health.
Socioeconomic factors may partially explain the link in moderately preterm infants, as low maternal education appeared to increase the effect on the risk for ADHD. "In this study, low maternal education is most probably a marker for a complex web of risk factors associated with social adversity, such as relative poverty, living in low status housing areas and family discord," note the authors.
Lindström K, et al "Preterm birth and attention-deficit/hyperactivity disorder in schoolchildren"Pediatrics 2011; 127: 858–865.