Nearly-term babies have elevated risk for ADHD

By Kathryn Doyle

(Reuters Health) - Very premature babies are known to have an increased risk for attention-deficit hyperactivity disorder (ADHD), and a new study suggests this may be true also for babies born only slightly early.

"There has been quite a lot of research on very preterm birth and the increased risk for ADHD but less evidence when it comes to late preterm birth (weeks 34-36) and even less regarding babies born early term (weeks 37-38)," lead author Dr. Minna Sucksdorff of the University of Turku in Finland, told Reuters Health by email.

The researchers used three Finnish health registries to identify 10,321 children diagnosed with ADHD who had been born between 1991 and 2005. They compared each child with ADHD to four children without ADHD who had a similar birth date, gender and place of birth.

The registries included data on gestational age at birth, which was calculated using the mother's last menstrual period and first trimester ultrasound.

Based on standards for each week of gestational age, the researchers noted which babies had been born of average weight, smaller than average or larger than average.

Mother's age, substance abuse and smoking during pregnancy, number of previous births, marital status, father's age, and the urbanity of the child's birthplace were associated with gestational age, birth weight and ADHD, the authors reported online August 24 in Pediatrics.

Accounting for other factors, premature birth was still associated with ADHD, with the risk increasing steadily as gestational age decreased.

Babies born at 25 weeks gestational age were more than five times more likely to be diagnosed with ADHD as those born at 40 weeks.

At 38 weeks, babies were about 12% more likely to develop ADHD than those born full term.

Infants born significantly small or large for their gestational age also had an increased risk of ADHD.

This is not surprising, said Guilherme Polanczyk of the University of Sao Paulo Medical School in Brazil, as there is good evidence showing that prematurity and poor fetal growth are associated with a variety of chronic disorders such as high blood pressure, cardiovascular disease, diabetes, and mental disorders, including ADHD.

The fact that even some early term babies, who would not be considered premature, had an increased risk may indicate that the risk is continuous, with no specific cut-off point, he said by email.

"It is very interesting that those big for gestational age also have an increased risk," he said. "This is consistent with a large body of evidence showing that deviations of brain development may also occur in this population, probably because of different disease mechanisms."

"It is more and more established that prenatal health is very important also for mental, emotional, and cognitive development," added Polanczyk who was not involved in the study. "Preventing preterm birth is always an important goal, because it has a causal role to a variety of other negative outcomes."

Identifying children with increased ADHD risk may improve early detection and intervention, which can help reduce the adverse outcomes of ADHD, he said.

SOURCE: http://bit.ly/1NPjxue

Pediatrics 2015.

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