Trends in the clinical characteristics of the U.S. cystic fibrosis patient population from 1995 to 2005

Rationale: Respiratory signs and symptoms (cough, sputum production, or crackles) are considered bellwethers of underlying cystic fibrosis (CF) lung disease. If respiratory signs and symptoms predict future lung function loss, then improvements in population lung function over the past decade should have been paralleled by a decrease in the prevalence of these variables in the same population. Additionally, changes in these variables over the past decade may provide insight into the improving health of the CF population. Methods: Cross-sectional data from the Epidemiologic Study of Cystic Fibrosis for each year between 1995 and 2005 were analyzed to characterize changes in pulmonary function and respiratory signs and symptoms over time. Patients were separated into five age groups: <6, 6-12, 13-17, 18-24, and ≥25 years. Results: Serial cross-sectional analyses of an average of 13,381 patients per year indicated that mean pulmonary function for the CF population improved and the percent of patients reporting cough or sputum production or having crackles or wheeze at their clinic visit decreased over the study period. Observed changes in pulmonary function were not consistently mirrored by changes in symptoms, which differed as a function of the variable studied and the age group. Conclusions: Reductions in respiratory signs and symptoms have paralleled improvements in pulmonary function. Both the absolute and relative magnitude of changes in prevalence for cough, sputum production, crackles, and wheeze differed among age groups and among variables. These results suggest the possibility that differences in respiratory signs and symptoms may arise from different underlying pathologies and may be influenced differently by therapeutic interventions.