Predictors of physical and mental health-related quality of life in patients with interstitial lung disease: a multifactorial analysis

Objective: To determine predictors of health-related quality of life (HRQoL) in patients with interstitial lung disease (ILD). Methods: A cross-sectional study comprising 63 patients, all of whom underwent lung function testing and the six-minute walk test. The following instruments were used: the Medical Outcomes Study 36-item Short-form Survey (SF-36), the Saint George's Respiratory Questionnaire (SGRQ), the Beck Anxiety Inventory, the Beck Depression inventory, and the Modified Medical Research Council Dyspnea Scale. Principal component analysis was used in order to reduce the dimensionality of the data, thereby identifying the predictor variables, and multiple linear regression analysis was used in order to identify the explanatory variables. Results: Of the 63 patients, 34 were female. The mean age was 60.1 +/- 13.3 years, the mean FVC was 64.17 +/- 15.54% of predicted, and the mean DLCO was 44.21 +/- 14.47% of predicted. All of the patients evaluated had impaired HRQoL, scoring worst for the SF-36 physical functioning and SGRQ activity domains. Of the patients evaluated, 60.3% and 57.1% showed symptoms of anxiety and depression, respectively. The principal component analysis identified one predictor of physical HRQoL and one predictor of mental HRQoL. Depression had a strong influence on the predictor of mental HRQoL, and the degree of dyspnea had a strong influence on both predictors of HRQoL in the patients evaluated. Variables related to lung function, exercise capacity, and anxiety had no impact on these predictors. Conclusions: In our sample of patients with ILD, the degree of dyspnea had a major impact on the physical and mental HRQoL, and depression had an impact on mental HRQoL.