Functional Comorbidity Index in Sleep Apnea

Abstract

Objectives (1) Measure the association between the Functional Comorbidity Index (range, 0-18) and physical function health status (SF-36 Physical Function domain), general physical health status (SF-36 Physical Component Score), and general mental health status (SF-36 Mental Component Score) outcome measures in a cohort of sleep apnea patients. (2) Test if the Functional Comorbidity Index is more strongly associated (a better predictor) than the well-known Charlson Comorbidity Index (range, 0-37) with these SF-36 outcome measures. Study Design Cross-sectional study. Setting University of Washington Sleep Center. Subjects and Methods In a cohort of newly diagnosed obstructive sleep apnea patients (N = 233), we obtained scores for the Functional Comorbidity Index, Charlson Comorbidity Index, and SF-36. We calculated Spearman correlations and adjusted coefficients of determination ( R2) with multiple linear regression, adjusted for demographic and health covariates. Bootstrapping generated R2 distributions for statistical comparison. Results Functional Comorbidity Index scores (mean ± standard deviation 2.4 ± 1.7) were more widely distributed than Charlson Comorbidity Index scores (0.7 ± 1.4). The Functional Comorbidity Index was significantly correlated with SF-36 Physical Function (–0.53, P < .001), Physical Component Score (–0.44, P < .001), and Mental Component Score (–0.38, P < .001). The Functional Comorbidity Index was a better predictor than the Charlson Comorbidity Index of SF-36 Physical Function ( R2 mean ± standard error 0.27 ± 0.05 vs 0.17 ± 0.05, P < .001), Physical Component Score (0.23 ± 0.05 vs 0.17 ± 0.05, P < .001), and Mental Component Score (0.23 ± 0.05 vs 0.13 ± 0.05, P < .001). Conclusion The Functional Comorbidity Index is a more robust predictor of general health status than the Charlson Comorbidity Index in obstructive sleep apnea patients.