Improved survival at low lung function in cystic fibrosis: cohort study from 1990 to 2007

Abstract

Objectives: To evaluate the survival of patients with cystic fibrosis whose lung function has deteriorated to a forced expiratory volume in one second (FEV(1)) below 30% predicted in the recent treatment era and to explore factors associated with any change in survival. Design Cohort study.

Setting: Adult cystic fibrosis unit in London.

Participants: 276 patients (147 (53%) male) whose FEV(1) was first observed to be less than 30% predicted between 1 January 1990 and 31 December 2003.

Main outcome measure: Survival during follow-up to 31 December 2007 in two year sub-cohorts.

Results: Median survival improved from 1.2 years in the 1990-1 group to 5.3 years in the 2002-3 group, with a marked improvement in survival from 1994. The use of nebulised recombinant human DNase was significantly associated with a reduced risk of death (hazard ratio 0.59, 95% confidence interval 0.44 to 0.79). Significantly increased risks were associated with a body mass index under 19 (hazard ratio 1.52, 1.10 to 2.10), long term oxygen therapy (3.52, 2.49 to 4.99), and nebulised antibiotics (1.84, 1.05 to 3.22).

Conclusion: A marked improvement has occurred in the survival of patients with cystic fibrosis with an FEV(1) less than 30% predicted. Secondary analyses suggest that some of this improvement may be due to use of recombinant human DNase.

Fig 1 Kaplan-Meier survival curves subdivided into seven two year sub-cohorts from 1990 to 2003, showing survival up to 31 December 2007

Fig 2 Selected measures of disease status and important treatment modalities at time of entry to cohort shown as percentages, with corresponding unadjusted hazard ratios for death in each sub-cohort. BMI=body mass index