The bodies of many premature babies do not yet make a chemical that keeps the lungs from collapsing when the infants exhale. Respirators keep them breathing but can stretch the fragile lungs. This causes inflammation and other damage, contributing to chronic lung disease.
To prevent chronic lung disease, doctors often give these babies the steroid dexamethasone to reduce inflammation.
To check its long-term safety, doctors at six hospitals in Taiwan looked at 146 school-age children who had been born prematurely and put on breathing machines. The children had been given dexamethasone or dummy shots for four weeks as infants.
As babies, 15 percent of those given dexamethasone developed chronic lung disease, compared with 28 percent of those who got placebos.
But eight years later, the children who had been on the steroid were shorter than the others by about an inch and a half, they were less coordinated, and they had lower IQ scores, Dr. Tsu-Fuh Yeh of China Medical University in Taiwan reported in Thursday's New England Journal of Medicine.
"Dexamethasone is widely used. Some doctors use dexamethasone like water. Not only in North America — in Europe, in Asia," he said.
Yeh said the long-term risks clearly outweigh the benefits. Although many people had known there might be long-term effects, he said, "because nobody's proved it, they still use it. Our paper is quite conclusive."
All premature babies are at risk for brain damage. But the 72 children who had been given dexamethasone had IQs an average of five points lower than the 74 who had received the dummy shots. They were also more easily distracted `n` scored an average of three points lower on a 36-point arithmetic test.
Those differences did not affect the youngsters' schoolwork. That is probably because many Taiwanese families with disabled children hire tutors or send them to special classes to help them catch up, Yeh said.
It is not clear exactly how widely dexamethasone is used. Over the past few years, three major pediatric associations in the United States, Canada and Europe — including the American Academy of Pediatrics — have recommended against using the steroid in premature babies, because of side effects that include holes in the stomach or intestine. Other types of steroids are available.
Dr. Alan Jobe of Cincinnati Children's Hospital Medical Center said the findings indicate that doctors need to be very cautious with any steroids given to premature babies, and that more tests are needed to find the safest way to give them.
Nearly one-third of the smallest babies who make it out of the hospital suffer from chronic lung disease. They are more prone to lung infections. Some need months on breathing machines or extra oxygen.
Jobe and Dr. Richard Auten of Duke University said doctors today are most likely to use steroids as a last resort and to use much less than the Taiwanese babies got. In very tiny babies, he said, doctors are more likely to use lower doses of a less potent steroid called hydrocortison.
Two U.S. surveys in 2002 found that about one-fifth of all babies with respiratory distress syndrome got some sort of steroid at some point in their treatment, Jobe said. The surveys did not ask which steroid was used, or how much of it and for how long.
Steroids have been proven to help these babies who are developing chronic lung disease — but tests are needed to find the lowest possible doses, and to see how these children do in the long term, Jobe said.
"The bottom line is that very few of the drugs used in preterm infants have ever been tested for use in preterm infants," he said.