Year-to-year changes in lung function in individuals with cystic fibrosis

Background We examined the year-to-year change in FEV1 for individuals and the overall cystic fibrosis population to better understand how individual trends may differ from population trends. Methods We calculated individual yearly changes using the largest annual FEV1 percent predicted (FEV1%) measurement in 20,644 patients (6–45years old) included in the Epidemiologic Study of Cystic Fibrosis. We calculated yearly population changes using age-specific medians. Results FEV1% predicted decreased 1–3 points per year for individuals, with maximal decreases in 14–15year olds. Population changes agreed with individual changes up to age 15; however after age 30, yearly population change approximated zero while individual FEV1% predicted decreases were 1–2 points per year. Conclusions Adolescents have the greatest FEV1% predicted decreases; however, loss of FEV1 is a persistent risk in 6–45year old CF patients. Recognizing individual year-to-year changes may improve patient-specific care and may suggest new methods for measuring program quality.