Prevalence, incidence, and factors associated with chronic cough: a systematic review and meta-analysis

Abstract

Introduction: Chronic cough (CC) is a common and disabling symptom, associated with physical and psychological effects that interfere with patients’ daily activities. Previous studies showed that CC may be present in people without any underlying condition and that environmental and occupational factors increase the risk of developing CC. However, the prevalence and incidence of CC in the general population and in groups exposed to potential risk factors have been scarcely investigated. Objective: We aimed to study the prevalence and incidence of CC (productive and non-productive) in the general population and in people exposed to specific environmental (i.e., fumes, smoke, dust) or occupational (i.e., factories, farms, and mines) factors, which have shown to be associated with CC. Methods: A systematic literature review was conducted (ref.: CRD42022298240) and searches were performed in CENTRAL, CINAHL Plus with Full Text, MEDLINE ALL, SCOPUS, and Web of Science. Studies were included if investigated adults with CC (>8 weeks) and reported on its prevalence/incidence or exposure to potential environmental and occupational factors. Two independent reviewers assessed the titles, abstracts and full-texts according to the eligibility criteria. Data on prevalence/incidence and exposure factors of CC were extracted. Evidence of publication bias was assessed with the Risk Of Bias In Non-randomized Studies – Exposures scale by two reviewers. Results: Sixty studies were included, 59 reported on the prevalence, nine on the incidence and 46 on exposing factors related to CC. The prevalence of productive CC in the general population was 6.3% to 13.7% (n = 5) and of non-productive CC was 0.2% to 37% (n = 11). The incidence of productive CC was 6.9% (cumulative, n = 1) and of nonproductive CC varied from 6.1-34.7% (cumulative, n = 2) to 38-67% (non-cumulative, n = 1). Studies reporting factors associated to CC showed a prevalence of productive CC of 3 to 51% in the exposed group and of 1% to 20.6% in the unexposed group (n = 8). Non-productive CC showed a prevalence of 1.3% to 65.4% in the exposed group and of 0% to 69.5% in the unexposed group (n = 21). The incidence of productive CC varied from 2.2% (non-cumulative) to 9% (cumulative) in the exposed group and 1% (non-cumulative) to 6.6% (cumulative) in the unexposed group (n = 1), whilst the incidence of non-productive CC ranged from 11.3% to 70% in the exposed and from 6.3% to 49.8% in the unexposed groups (cumulative, n = 4). Factors associated with higher prevalence and incidence of CC were dusts, gases or fumes, biological and mineral dust in occupational exposures and pesticides and smoke in environmental exposures. Conclusions: Chronic cough affects up to 37% of the general population. People exposed to dusts, gases or fumes, biological and mineral dust, pesticides, and smoke seem to be the most affected by CC, especially non-productive cough. Addressing these factors seems of paramount importance in the treatment of people with CC.