Is chronic cough an additional marker for lung function decline?

Abstract

Rationale: Recent studies show that the CT measured total airway count (TAC) is reduced in COPD and is associated with FEV1 decline over time. In addition to TAC, we aimed to investigate whether chronic cough is an independent determinant of FEV1 decline.

Methods: From CanCOLD, a Canadian multi-center, population-based study, 1183 participants aged ≥40 years were included: 286 were never-smokers with normal lung function, 297 ever-smokers with normal lung function at risk for COPD, and 600 with COPD of different severity stages (n = 361 GOLD I, n = 239 GOLD II-IV). CT imaging parameters included TAC and emphysema (LAA950= percentage of the lung with low attenuation areas below -950 Hounsfield units). Spirometry (FEV1) before and after bronchodilation according to ATS/ERS guidelines was done at four times (at baseline, after 18 months, 36 months, and 54 months). Linear mixed effects regression models were performed for determining longitudinal changes (in ml). Chronic cough was defined as cough on most days for at least 3 months in two consecutive years.

Results: Adjusted for age, sex, BMI, race, smoking status, and baseline FEV1, chronic cough was highly associated (p<0.0001) with FEV1 decline over time in the entire study population. This was preserved even after adjustment for TAC and emphysema (p<0.0001).

Conclusion: Our data indicate that chronic cough is - besides TAC and emphysema score -an independent determinant of decline in FEV1 in non-COPD and COPD subjects. Further studies are needed to assess underlying pathophysiological or structural characteristics behind chronic cough.