Asthma is a chronic lung condition that occurs widely in the US. According to the Centers for Disease Control and Prevention (CDC), around 25 million people (about 1 in 12) have asthma. This percentage is much higher in children; around 9.3% of children (6.8 million) are believed to have the condition.
The National Heart, Lung, and Blood Institute (NHLBI) have stated that inhaled corticosteroids (ICS) are the preferred medicine for long-term control of asthma, and that they are the most effective medicine for treating the inflammation and narrowing of the airways that are caused by the disease.
The NHLBI also state that young children who wheeze and develop respiratory infections frequently are most at risk from asthma. This fact suggests that the group of people who are most likely to require ICS are the same group who would be most affected by any growth suppressing side effects, should they be found to exist.
Inhaled corticosteroids and growth
A group of authors worked together on two systematic reviews of ICS, published by The Cochrane Library. One review focused on the effects of ICS on growth rates when compared with placebos or non-steroidal drugs, and the other review concentrated on investigating different dose levels.
The effect of ICS on growth
Inhaled corticosteroids are regarded as the best long-term form of asthma treatment but could come with a risk of growth suppression for children.
The first systematic review examined the results of 25 trials that involved a total of 8,471 children with mild to moderate asthma. Of the 25 trials, 14 - involving 5,717 of the participating children - measured growth over a year.
The majority of ICS were tested, and results suggested that they suppressed growth when measured against placebos or non-steroidal drugs. In these control groups, the average rate of growth was recorded as being around 6-9 cm a year, and in the groups receiving ICS, the average growth rate was reduced by 0.5 cm.
Linjie Zhang, from the Faculty of Medicine at the Federal University of Rio Grande, Brazil, and lead author of this review, says that the growth suppression "seems minor compared to the known benefits of the drugs for controlling asthma and ensuring full lung growth."
The effect of ICS dosage on growth
The second systematic review investigated the results of 22 trials in which asthmatic children were treated with low or medium doses of ICS, with the different trials testing varying doses of most of the available ICS. Of the 22 trials, only three followed the participating children for a year or longer, following 728 children. One of these trials also tested three different dosing plans.
In the three trials that reviewed the participants for a year or over, lower doses of ICS were found to improve growth by 0.25 cm a year.
Further studies required
The researchers found that across the different studies, growth suppression rates varied. The researchers could explain some of the variation on account of the different ICS being used, but as the drug types were indirectly compared, Zhang says "conclusions about the superiority of one drug over another should be confirmed by further trials that directly compare the drugs."
Another limitation found by the reviewing researchers was the length of time of the trials. Prof. Francine Ducharme, from the Department of Paediatrics at the University of Montreal, Canada, was the senior author of the second review and says:
"Only 14% of the trials we looked at monitored growth in a systematic way for over a year. This is a matter of major concern given the importance of this topic. We recommend that the minimal effective dose be used in children with asthma until further data on doses becomes available. Growth should be carefully documented in all children treated with ICS, as well in all future trials testing ICS in children."
The authors suggest that longer trials, trials directly comparing different doses and trials directly comparing different drugs are needed in order for the conclusions drawn from their systematic reviews to be fully authenticated.
Last month, Medical News Today reported on a study suggesting that infants who are exposed to allergens and bacteria during their first year of life are less likely to experience allergies, wheezing and asthma.