title: Longitudinal association between lung function and health-related quality of life in cystic fibrosis.
abstract: BACKGROUND
  Lung function is an important indicator of cystic fibrosis disease status and those with better forced expiratory volume in 1 s (FEV(1))% predicted have tended to report a better health-related quality of life (HRQoL) in cross-sectional studies. The relationship between lung function and HRQoL over time is unknown. This work assesses the natural progression of HRQoL reporting over many years and compares assessments across a whole decade and evaluates the relationship between lung function and HRQoL longitudinally.
  
  
  METHODS
  Demographic (age, gender), clinical (FEV(1)% predicted, body mass index, diabetes, Burkholderia cepacia complex, intravenous access device and nutritional status) and HRQoL (Cystic Fibrosis Quality of Life Questionnaire) variables were obtained every 2 years over a 12-year period (seven time points from 1998 to 2010).
  
  
  RESULTS
  HRQoL and lung function declined slowly over time and significant decade changes were observed for FEV(1)% predicted and the nine domains of the Cystic Fibrosis Quality of Life Questionnaire. The results of random coefficient modelling indicated that, at the population level, decreasing FEV(1)% predicted was associated with decreasing HRQoL after adjusting for confounding variables. However, the percentage of patients for whom a decrease in lung function was associated with a decrease in HRQoL differed according to the quality of life domain.
  
  
  CONCLUSIONS
  HRQoL and FEV(1)% predicted decline slowly; nevertheless, a decrease in lung function predicted a decrease in HRQoL over time.
authors.affiliation: School of Psychology, University of Central Lancashire, Preston, UK. jabbott@uclan.ac.uk
authors.forename: Janice
authors.initials: J
authors.lastname: Abbott
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Hurley
authors.forename: Alison M
authors.initials: AM
authors.lastname: Morton
authors.forename: Steven P
authors.initials: SP
authors.lastname: Conway
mesh_terms: D000293:Adolescent; D000328:Adult; D003550:Cystic Fibrosis / Q000503:physiopathology*; D005260:Female; D005541:Forced Expiratory Volume; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011788:Quality of Life; D055815:Young Adult