Depressive Symptoms Are Associated with Self-Reported Physical Limitations That Are Activity Dependent in a Cross-Sectional Analysis of Subjects with Chronic Obstructive Pulmonary Disease
One in four patients with chronic obstructive pulmonary disease (COPD) has depression. However, the effect of depressive symptoms on self-reported physical function among patients with COPD is not fully defined. We tested the hypothesis that depressive symptoms among patients with COPD are associated with increased self-reporting of physical limitations in a nationally representative sample of adults living in the USA. We sampled 775 adults with obstructive lung disease and history of regular smoking from 2007 to 2012 National Health and Nutrition Examination Survey (NHANES). Multivariable logistic regression was used to estimate odds ratios for the association between depressive symptoms and self-reported difficulty performing three activities. We used a Patient Health Questionnaire (PHQ-9) score ≥ 10 to define depressive symptoms. Covariates in the multivariable analysis were age, gender, percent predicted forced expiratory volume in 1 second, current smoking, low-income status, and number of co-morbidities. In models predicting any difficulty walking a quarter mile, walking up 10 stairs, and walking between rooms on a level surface, adjusted odds ratio estimates (95% CI) for depressive symptoms were 2.03 (1.06, 3.88), 3.40 (1.77, 6.50), and 4.92 (2.29, 10.60), respectively. The presence of depressive symptoms was associated with increased self-reported difficulty with physical activities in our sample. Unexpectedly, the effect of depressive symptoms was greater with easier activities in our sample. These results suggest that depressive symptoms are associated with activity-dependent self-reporting of physical limitations among patients with COPD.