An analysis released Friday by the Food and Drug Administration concluded that four drugs used to treat asthma are linked with an increased risk of asthma-related side effects, with higher risks seen in children. 

The drugs involved were GlaxoSmithKline PLC’s Serevent and Advair, Novartis AG’s and Schering-Plough Corp.’s Foradil and AstraZeneca PLC’s Symbicort. The drugs belong to a class of medications known as long-acting beta-agonists, or LABAs, and have been the subject of an ongoing FDA safety review.

The analysis involved 110 trials and 60,954 patients. The bulk of patients were from Serevent trials, with about 43,000 patients, the FDA said. There were 20 asthma-related deaths in the studies and of those, 16 were patients on Serevent and four were patients in the non-LABA group. The risk however “was not apparent when patients were also using inhaled corticosteroids, which current asthma treatment guidelines recommend.”

The drugs already carry strong warnings, but the findings could lead to more specific instructions for patients and greater restrictions on some of the medications. The analysis was prepared for an advisory committee meeting next week to discuss the safety of the drugs as a class. More exactly, the panel will be asked to vote on whether the drugs should continue to be marketed for children and adults.

Asthma is a chronic condition in which the airway occasionally constricts, becomes inflamed, and is lined with excessive amounts of mucus. It has become a problem in urban environments in the developed world, where up to one in four children are suffering from this condition. It is known in the medical field at least since Hippocrates in 450 BC.

Its causes are not fully understood, but a variety of combined factors is suspected. It appears that certain environmental and genetic factors may only affect asthma when combined. Some studies have linked asthma with the stress of a pregnant woman or with the violence some kids face during their childhood.