Cough in Adults with Undiagnosed Respiratory Symptoms

Abstract

Rationale: Cough is a common symptom of undiagnosed respiratory conditions.

Objective: To investigate cough in adults with undiagnosed respiratory symptoms and its association with quality of life (QoL), sleep quality, and healthcare utilization for respiratory illness.

Methods: We used a case-finding strategy to find community-dwelling adults with respiratory symptoms but no previous history of diagnosed lung disease. Pre- and post-bronchodilator spirometry determined if participants met diagnostic criteria for asthma, chronic obstructive pulmonary disease (COPD), preserved ratio impaired spirometry (PRISm), or if they had normal spirometry. Twelve questions from the Asthma Screening Questionnaire, COPD Assessment Test, and the St. George's Respiratory Questionnaire were used to develop a cough score. The 36-Item Short Form Survey (SF-36) and Global Sleep Assessment Questionnaire (GSAQ) were used to assess QoL and sleep quality, respectively.

Results: Adults with undiagnosed respiratory symptoms (N=2857, mean score 57.8, 95%CI 56.9-58.6) reported higher cough scores than age-matched controls (N=231, mean score 17.7, 95%CI 15.6-19.8). Participants found to have asthma (N=265, mean score 61.0, 95%CI 58.2-63.7) and COPD (N=330, mean score 61.8, 95%CI 59.3 to 64.3) had higher cough scores than those with PRISm (N=172, mean score 54.5, 95%CI 51.1-58.0) or normal spirometry (N=2090, mean score 57.0, 95%CI 56.0-58.0). Higher cough scores were associated with decreased QoL (lower SF-36 score, regression coefficient -0.19; 95%CI -0.22 to -0.17, P <0.001), worse sleep quality (higher GSAQ score, regression coefficient 0.16, 95%CI 0.14-0.18, P <0.001), and higher healthcare utilization for respiratory illness (incidence rate ratio 1.007, 95%CI 1.004-1.010, P <0.001).

Conclusions: In adults with undiagnosed respiratory symptoms, cough was most severe in those with undiagnosed asthma or COPD and was independently associated with worse quality of life, impaired sleep quality, and higher healthcare utilization for respiratory illness.