Describing results that contrast sharply with those from several prior observational studies by other biomedical scientists, investigators found that, in a large cohort of patients with chronic obstructive pulmonary disease (COPD), there was no significant effect from inhaled corticosteroid use on either patient mortality rate, the number of COPD exacerbations, or COPD-related hospital stays. Researchers presented data from 2,654 COPD patients who were prescribed inhaled corticosteroids for at least 80 percent of a 90-day period during the trial. There were 5,398 COPD patients who never had used inhaled corticosteroids also involved in the analysis. (COPD patients have a persistent obstruction of the airways associated with either severe emphysema or chronic bronchitis. The disease usually results from smoking.) The study authors said that they did not find a significant reduction in mortality for average inhaled steroid use at either a low, medium, or high dose. Nor did they see any association between inhaled corticosteroid use and reduced hospitalizations or exacerbations due to COPD. According to the authors, during a mean follow-up period of 544 days, 1,052 patients of the total included in the study died, 559 were hospitalized for COPD-associated symptoms, and 1,287 made an outpatient visit for a COPD exacerbation. The authors noted that several large prior observational studies had shown that inhaled corticosteorids, as used in clinical practice, were associated with a significant reduction in mortality or exacerbations. They attributed the difference in results to a statistical bias during the prior studies. The research is published in the second issue for December 2003 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.