ATLANTA – The perception of dyspnea among patients with chronic obstructive pulmonary disorder plays a bigger role in quality of life, functional status, and depression than do objective measures of disease severity, according to findings from cross-sectional study involving 158 patients.
The findings suggest that assessing and addressing dyspnea in COPD patients could play an important role in improving quality of life outcomes, Dr. Sandra Adams reported at the annual meeting of the American College of Chest Physicians.
The patients included in this analysis are part of the CASCADE study, a 2-year longitudinal observational study of genes and depression in COPD. They completed spirometry, the modified Medical Research Council (mMRC) dyspnea scale, questions related to exacerbation risk within the last year, the Chronic Respiratory Questionnaire (CRQ), a nine-item depression interview, the Personal Health Questionnaire (PHQ-9), and a 6-minute walk test at baseline.
Study participants had a mean age of about 67 years, about 25% were women, 40% were on supplemental oxygen, and the mean forced expiratory volume in 1 second (FEV1) percent predicted was 43%. Exacerbations were self-reported.
More than 60% had a self-reported physician diagnosis of depression.
About 20% of the patients were found to be grade A patients, based on the revised Global Initiative for Chronic Obstructive Lung Disease (GOLD) released in December 2011, about 10% were grade B patients, about 20% were grade C patients, and about 50% were grade D patients, said Dr. Adams of the University of Texas Health Science Center, San Antonio.
Patients with grade A disease have mild disease severity, airflow limitation, and few exacerbations; those with grade B disease are similar to those with grade A, except they have more symptoms (in this study, the grade B patients had no exacerbations). Those with grade C disease have minimal symptoms, severe airflow limitation, and/or two or more exacerbations each year; those with grade D disease are similar to those with grade C disease, except they have more symptoms.
"One thing we were actually really surprised to find is that the group of A and C with minimal symptoms may be a lot more similar than we think, whereas D and B with the severe symptoms – even though they have significant differences in exacerbations and/or airflow limitation, may be very similar," she said.
Indeed, no differences on the various measures used in this study were seen between the A and C patients, and between the B and D patients. But when the A and C patients were combined and compared with the combined group of B and D patients, significant differences emerged for every measure.
"Again, the big difference is symptoms; A and C have minimal symptoms and B and D have severe symptoms," Dr. Adams said.
As it turned out, grades A and C patients had significantly higher CRQ scores (higher scores are better) than did grades B and D patients (mean of 105 and 98 for A and C vs. 80 and 84 for B and D, respectively). Grades A and C also had statistically and clinically significantly greater 6-minute walk test distances, Dr. Adams noted.
On a physical function measure of steps walked in a day, the A and C patients averaged 7,900, and the B and D patients averaged only 4,800, she added.
That’s 3,900 fewer steps despite inclusion of B-group patient (10% of the total study population) in the B/D combined group, Dr. Adams noted.
"Again ... grade B had relatively normal lung function and no exacerbations, but yet they’re severely dyspneic," she noted.
As for depression, the history was similar across all grades, although more grade B and D patients than A and C patients had PHQ-9 scores of 10 or greater, which indicates significant depression. On linear regression, an mMRC dyspnea scale score of 2 or higher was associated with a significant increase in depression (odds ratio, 2.8).
"So the bottom line to this is grades A and C have similar levels of depression, quality of life, physical function, and physical activity despite significant differences in FEV1 percent predicted and and/or the number of exacerbations," she said, explaining that it appears that the perception of dyspnea is the main factor associated with these outcomes.
"And, in fact, those who report severe dyspnea may be even more limited than those with frequent exacerbations," she said.
What are the clinical implications of the findings?
"We ask our patients, ‘How are you doing? How is your shortness of breath?’ but actually getting an assessment and also trying to really address the dyspnea in addition to the exacerbations is going to be really key in this population," Dr. Adams concluded.