Asthma drugs may suppress children's growth, according to a recent study.

Researchers found that children's growth slowed in the first year of treatment with corticosteroid drugs which are administered via inhalers to children.

Inhaled corticosteroids are prescribed as first-line treatments for adults and children with persistent asthma. They are the most effective drugs for controlling asthma and have reduced asthma deaths, hospital visits and the number and severity of exacerbations, and improve quality of life.

For the study, researchers conducted two systematic reviews.

The first review focused on 25 trials involving more than 8,000 children up to 18 years old with mild to moderate persistent asthma. These trials tested all available inhaled corticosteroids except triamcinolone and showed that, as a group, they suppressed growth rates when compared to placebos or non-steroidal drugs. Fourteen of the trials, involving 5,717 children, reported growth over a year. The average growth rate, which was around 6 to 9 cm per year in control groups, was reduced by about 0.5 cm in treatment groups.

"The evidence we reviewed suggests that children treated daily with inhaled corticosteroids may grow approximately half a centimeter less during the first year of treatment," Linjie Zhang, lead author of the review, said in a statement. "But this effect is less pronounced in subsequent years, is not cumulative, and seems minor compared to the known benefits of the drugs for controlling asthma and ensuring full lung growth."

In the second review, the research team reviewed data from 22 trials in which children were treated with low or medium doses of inhaled corticosteroids. These trials tested different doses of all drugs except triamcinolone and flunisolide. Only three trials followed 728 children for a year or more, with one of these trials testing three different dosing regimens. In the three trials, using lower doses of the inhaled corticosteroids, by about one puff per day, improved growth by a quarter of a centimeter at one year.

Researchers found that growth suspension varied across studies, and so they looked at the relationship between a variety of factors and their effects on growth.

They said some of the variation could be explained by the drugs used, although since this was an indirect comparison the authors say more evidence is needed.

"Conclusions about the superiority of one drug over another should be confirmed by further trials that directly compare the drugs," Zhang said

The findings were recently published in The Cochrane Library.