Cough in Adults with Undiagnosed Respiratory Symptoms

Rationale: Cough is a common symptom of undiagnosed respiratory conditions. Objectives: 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 postbronchodilator spirometry determined if participants met diagnostic criteria for asthma, chronic obstructive pulmonary disease (COPD), or preserved ratio impaired spirometry, 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 and Global Sleep Assessment Questionnaire were used to assess QoL and sleep quality, respectively. Results: Adults with undiagnosed respiratory symptoms (n = 2,857; mean score, 57.8; 95% confidence interval [CI], 56.9 to 58.6) reported higher cough scores than age-matched control subjects (n = 231; mean score, 17.7; 95% CI, 15.6 to 19.8). Participants found to have asthma (n = 265; mean score, 61.0; 95% CI, 58.2 to 63.7) and COPD (n = 330; mean score, 61.8; 95% CI, 59.3 to 64.3) had higher cough scores than those with preserved ratio impaired spirometry (n = 172; mean score, 54.5; 95% CI, 51.1 to 58.0) or normal spirometry (n = 2,090; mean score, 57.0; 95% CI, 56.0 to 58.0). Higher cough scores were associated with decreased QoL (lower 36-Item Short Form Survey score; regression coefficient, -0.19; 95% CI, -0.22 to -0.17; P < 0.001), worse sleep quality (higher Global Sleep Assessment Questionnaire score; regression coefficient, 0.16; 95% CI, 0.14 to 0.18; P < 0.001), and higher healthcare utilization for respiratory illness (incidence rate ratio, 1.007; 95% CI, 1.004 to 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 QoL, impaired sleep quality, and higher healthcare utilization for respiratory illness.