Functional Comorbidity Index and health-related quality of life in patients with obstructive sleep apnea

Introduction: The role of comorbidities in determining health-related quality of life (HRQL) in obstructive sleep apnea (OSA) patients has not been thoroughly investigated. Commonly used comorbidity tools, such as Charlson Comorbidity Index (CCI), have been designed with mortality as the outcome variable. A new tool, the Functional Comorbidity Index (FCI), has been especially developed to assess the effect of comorbidities on the "physical functioning" subscale of the Medical Outcomes Short Form-36 Health Survey (SF-36). 1) To determine the role of FCI in the prediction of the effect of comorbidities on HRQL in OSA. 2) To determine whether FCI and CCI are equally robust in predicting the effect of comorbidities on HRQL in OSA. Material and methods: Two hundred and fifty-five OSA patients were enrolled. Patients completed the SF-36 and the Medical Outcomes Study Sleep Scale (MOS-SS) forms, while their comorbidity status was assessed by FCI and CCI. The SF-36 physical (PCS-36) and mental component summary (MCS-36) scores were also calculated. Results: PCS-36 was predicted by FCI (p < 0.001), male gender (p = 0.001), BMI (p = 0.002) and the "awakening with "breathlessness/headache" MOS- SS subscale (p = 0.011) (R-2 = 0.348). Among these predictors, FCI exerted the most important quantitative effect. MCS-36 was predicted only by the "sleep disturbance" (p = 0.005) and the "awakening with breathlessness/headache" MOS-SS subscales (p < 0.001) (R-2 = 0.221). Conclusions: In patients with OSA, FCI is an independent predictor of the physical aspect of their HRQL. FCI is more robust than CCI in assessing the effect of comorbidities on HRQL in OSA.