The Johns Hopkins University study also found that while inhalers helped, they did not extend a patient's life after a year of use, The Baltimore Sun reported Wednesday.

While medical experts have known for years that inhalers are effective in treating wheezing and breathlessness brought on by chronic obstructive pulmonary disease, doctors raised questions about steroid inhalers' side effects and whether they extended a patient's life, said the study's lead author, M. Bradley Drummond, a pulmonologist at the Johns Hopkins School of Medicine.

In the study, investigators examined 11 clinical trials, including 14,426 patients, comparing the incidence of pneumonia in those who used inhalers against those who did not.

Researchers said they weren't sure why inhalers increased the risk of pneumonia, but one theory is that they may weaken a person's immune system.

"Because these agents are so effective at controlling symptoms, we do feel there is a good role for inhaled steroids for treating COPD," Drummond said. "But for some patients there may be more harm than benefits."

Drummond said patients who use inhalers should not stop doing so, but talk with their physicians if they have concerns.