, according to research published in CHEST.
The results indicate “that chronic cough in individuals with COPD is associated with a more severe disease phenotype, which could be helpful for stratifying management of COPD in the future,” wrote Eskild Landt, PhD, a research assistant at Zealand University Hospital in Køge, Denmark, and colleagues.
A study by published in the Journal of Allergy and Clinical Immunology: In Practice (2019;7[6]:1783-92.e8) indicated that in patients with asthma, chronic cough was associated with worse respiratory symptoms, more health care utilization, decreased lung function, and increased inflammatory markers in blood. Dr. Landt and colleagues hypothesized that patients with COPD and chronic cough had a similar pattern of disease severity.
To test their hypothesis, they identified individuals with COPD and chronic cough among 43,271 participants in the Copenhagen General Population Study, a population-based cohort study. The researchers defined COPD as a ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) of less than 0.70 in individuals without asthma. Consecutive individuals answered questions about chronic cough, which was defined as a cough lasting more than 8 weeks, and responded to the Leicester Cough Questionnaire. They also underwent a physical health examination, including prebronchodilatory spirometry, and gave blood for biochemical analyses. The blood was analyzed for high-sensitive C-reactive protein, fibrinogen, leukocytes, eosinophils, neutrophils, and immunoglobulin E (i.e., inflammatory biomarkers).
Dr. Landt and colleagues identified 8,181 patients (19% of the population) with COPD, 796 (10%) of whom had chronic cough. Of the 33,364 participants without COPD, 1,585 (5%) had chronic cough. For patients with COPD and chronic cough, median total Leicester Cough Questionnaire score was 17.7, corresponding to 5.9 for the physical domain, 5.6 for the psychological domain, and 6.3 for the social domain.
Among participants with COPD, those with chronic cough had higher rates of sputum production (60% versus 8%), wheezing (46% versus 14%), dyspnea (66% versus 38%), chest pain or tightness (9% versus 4%), nighttime dyspnea (8% versus 3%), episodes of acute bronchitis or pneumonias in the past 10 years (45% versus 25%), and general practitioner visits in the past 12 months (53% versus 37%). In addition, these participants had lower FEV1% of predicted (81% versus 89%), lower ratio of FEV1 to FVC (0.64 versus 0.66), and higher levels of high-sensitive C-reactive protein, fibrinogen, leukocytes, neutrophils, eosinophils, and immunoglobulin E in blood.
“To our knowledge, this is the first study reporting Leicester Cough Questionnaire score for randomly selected individuals with COPD from a general population setting,” wrote Dr. Landt and colleagues. The study’s strengths include its randomly chosen population-based sample and investigator blinding to disease status and clinical outcome, they added. Some patients with the most severe types of COPD and chronic cough may not have attended the physical examination and participated in the study, however, and this factor could have biased the results. Furthermore, nearly the entire sample was white, so the results may not be generalizable to other ethnicities. “That said, we are not aware of results to suggest that our findings should not be relevant to individuals of all races,” wrote the investigators.
The study was funded by the private Lundbeck Foundation, as well as by the Danish Lung Association and the Danish Cancer Society. Several authors reported receiving grants and fees from AstraZeneca, GlaxoSmithKline, and Novartis that were unrelated to the study.
SOURCE: Landt E et al. CHEST. 2020 Jan 24. doi: 10.1016/j.chest.2019.12.038.