Validation of the Cough Phenotype TBQ among Elderly Finnish Subjects

Background: Phenotypes are defined as the observable properties of disorders that are produced by the interactions of the genotype and the environment. The approaches to phenotype disorders have evolved from subjective expert opinion to data-driven methodologies. A previous cluster analysis among working-age subjects with cough revealed a phenotype TBQ (Triggers, Background disorders, Quality of life impairment), which included 38% of the subjects with cough. The present study was carried out to validate this phenotyping among elderly, retired subjects with cough. Methods This was an observational, cross-sectional study conducted via email among the members of the Finnish Pensioners` Federation (N = 26 205, 23.6% responded). The final analysis included 1109 subjects with current cough (mean age 72.9 years (range 64–90 years) with 67.7% females). All filled in a comprehensive 86-item questionnaire including the Leicester Cough Questionnaire. Phenotypes were identified utilizing K-means partitional clustering. Results Two clusters were identified. The cluster A included 75.2% and cluster B 24.8% of the subjects. The three most important variables to separate the clusters were the number of the cough triggers (mean 2.47 (SD 2.34) vs. 7.08 (3.16), respectively, p < 0.001), Leicester Cough Questionnaire physical domain (5.38 (0.68) vs. 4.21 (0.81), respectively, p < 0.001), and the number of the cough background disorders (0.82 (0.78) vs. 1.99 (0.89), respectively, p < 0.001). Conclusion The phenotype TBQ could be identified also among elderly, retired subjects with cough, thus validating the previous phenotyping among working-age subjects. The main underlying pathophysiological feature separating the phenotype TBQ from the rest of the coughing subjects is probably hypersensitivity of the cough reflex arc.