Effects of depressive symptoms on health-related quality of life in asthma patients

Abstract

Objective: To assess the effects of depressive symptoms on asthma patients' reports of functional status and health-related quality of life.

Design: Cross-sectional study.

Setting: Primary care internal medicine practice at a tertiary care center in New York City.

Patients: We studied 230 outpatients between the ages of 18 and 62 years with moderate asthma.

Measurements and main results: Patients were interviewed in person in English or Spanish with two health-related quality-of-life measures, the disease-specific Asthma Quality of Life Questionnaire (AQLQ) (possible score range, 1 to 7; higher scores reflect better function) and the generic Medical Outcomes Study SF-36 (general population mean is 50 for both the Physical Component Summary [PCS] score and Mental Component Summary [MCS] score). Patients also completed a screen for depressive symptoms, the Geriatric Depression Scale (GDS), and a global question regarding current disease activity. Stepwise multivariate analyses were conducted with the AQLQ and SF-36 scores as the dependent variables and depressive symptoms, comorbidity, asthma, and demographic characteristics as independent variables. The mean age of patients was 41 +/- SD 11 years and 83% were women. The mean GDS score was 11 +/- SD 8 (possible range, 0 to 30; higher scores reflect more depressive symptoms), and a large percentage of patients, 45%, scored above the threshold considered positive for depression screening. Compared with patients with a negative screen for depressive symptoms, patients with a positive screen had worse composite AQLQ scores (3.9 +/- SD 1.3 vs 2.8 +/- SD 0.8, P <.0001) and worse PCS scores (40 +/- SD 11 vs 34 +/- SD 8, P <.0001) and worse MCS scores (48 +/- SD 11 vs 32 +/- SD 10, P <.0001) scores. In stepwise analyses, current asthma activity and GDS scores had the greatest effects on patient-reported health-related quality of life, accounting for 36% and 11% of the variance, respectively, for the composite AQLQ, and 11% and 38% of the variance, respectively, for the MCS in multivariate analyses.

Conclusions: Nearly half of asthma patients in this study had a positive screen for depressive symptoms. Asthma patients with more depressive symptoms reported worse health-related quality of life than asthma patients with similar disease activity but fewer depressive symptoms. Given the new emphasis on functional status and health-related quality of life measured by disease-specific and general health scales, we conclude that psychological status indicators should also be considered when patient-derived measures are used to assess outcomes in asthma.

FIGURE 1

Medical Outcomes Study SF-36 and Asthma Quality of Life Questionnaire (AQLQ) scores according to depressive symptoms measured by the Geriatric Depression Scale. SF-36 Physical Component Summary (PCS) and Mental Component Summary (MCS) scores are based on a mean score of 50 in the general population. The composite AQLQ score is transformed to range from 0 (worst score) to 100 (best score) according to the following equation: [(Raw Score − Minimum Possible Score)/Possible Score Range]× 100. For both the SF-36 and the AQLQ, higher scores reflect better condition.