A register-based study: cough - a frequent phenomenon in the adult population.

Background: Chronic cough, more than 8 weeks, can either be without co-morbidity called unexplained chronic cough (UCC) or with co-morbidity called refractory chronic cough (RCC). Using datasets from the Danish National Prescription Registry (Prescription Registry) and Danish National Patient Registry (Patient Registry) we wanted to investigate the prevalence and factors of importance of cough in a Nationwide registry.

Material And Methods: Inclusion criteria were patients 18-90 years with at least one final cough diagnosis (ICD-10 DR05/DR059) in Patient registry or patients who have redeemed ≥2 prescriptions for relevant cough-medication within a 90-day harvest in the Prescription registry from 2008 to 2017. To validate this study's chosen proxy on chronic cough an analysis of the Patient registry sub-population with a contact of ≥8 weeks and then final diagnosis code DR05/DR059 was also performed. The population was divided into UCC and RCC.

Results: Of the 104,216 patients from the Prescription registry, 52,727 were classified as having UCC and 51,489 were classified with RCC. From the Patient registry 34,260 were included, of whom 12,278 had UCC and 21,982 had RCC. Cough were frequently found among females (p < 0.0001). Both genders were around 2 years older in RCC than UCC (p < 0.0001) Spirometry was performed in 69 and 57%, X-ray in 73 and 58% and asthma challenge test performed in 13 and 5% (UCC and RCC, respectively, p < 0.0001). The frequency of co-morbidities such as heart failure, rheumatologic disease, pulmonary embolism, and diabetes was < 10%.

Conclusion: Many patients suffer from chronic cough or cough requiring medications, with or without co-morbidity; frequently found among menopausal women. Most patients had a substantial work-up performed. The high frequency and the resources consuming work-up program call for systematic coding of disease, systematic patient evaluation and more specific treatment options. The study was approved (ID: no. P-2019-191).