Abstract
Purpose :
Exfoliation syndrome (XFS) is a disorder of elastin metabolism that is characterized by accumulation of fibrillar, extracellular material and is associated with the LOXL1 locus. LOXL1 knockout mice develop emphysematous changes (Liu et al 2004). Since patients with COPD have increased elastin degradation we examined the impact of XFS on patients developing COPD and their survival.
Methods :
Retrospective, cross-sectional design using the University of Utah Health Care System database of patients ≥ age 40 seen between 1996-2014. Clinical Modification (ICD-9) diagnosis and Current Procedural Terminology (CPT) codes were used to identify subjects with a history of XFS or COPD. We identified 3,099 with XFS, 23,550 with COPD, and 165 with XFS and COPD. Controls were matched to patients 5:1 on age and sex. Conditional logistic regression, including body mass index categories and ever/never smoked as covariates, was performed. Models with and without a multiplicative interaction term of XFS and smoking status were examined. A case–case comparison within XFS patients determined if the risk of COPD differed between smokers and nonsmokers. Log-rank test was used for survival analysis.
Results :
XFS was associated with a 24% increased risk of having a diagnosis of COPD after adjusting for all variables (OR=1.24, 95%CI 1.02-1.50; p=0.03). The addition of an interaction term of smoking and XFS did not improve model fit according to a likelihood ratio test. Smoking conferred a ~5-fold increased risk of COPD independent of the main effect of XFS. In a case-case comparison of XFS patients, the risk of COPD in XFS patients who smoked was 6.3-fold greater than in nonsmoking XFS patients. Using a Mantel-Haenszel chi-square test, COPD patients with XFS were significantly more likely to be alive at last follow up if they had COPD and XFS compared with COPD patients with no XFS history (61.2% vs 54.7%). This was supported with a COPD survival curve (Fig 1).
Conclusions :
XFS patients are at an increased risk of developing COPD compared to their respective controls. Similarly, XFS smokers are at an increased risk of COPD versus non XFS smokers. Interestingly, XFS patients with COPD appear to live longer than non XFS COPD patients. Additional research is needed to determine if the etiology of XFS and COPD are related, and how tobacco exposure modulates this relationship.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.