Longitudinal cough frequency monitoring in persistent coughers:Daily Variability and Predictability

Abstract Purpose We determined the cough counts and their variability in subjects with persistent cough for 30 days. Methods The Hyfe cough tracker app uses the mobile phone microphone to monitor sounds and recognizes cough with artificial intelligence-enabled algorithms. We analysed the daily cough counts including the daily predictability rates of 97 individuals who monitored their coughs over 30 days and had a daily cough rate of at least 5 coughs per hour. Results The mean (median) daily cough rates varied from 6.5 to 182 (6.2 to 160) coughs per hour, with standard deviations (interquartile ranges) varying from 0.99 to 124 (1.30 to 207) coughs per hour among all subjects. There was a positive association between cough rate and variability, as subjects with higher mean cough rates (OLS)have larger standard deviations. The accuracy of any given day for predicting all 30 days is the One Day Predictability for that day, defined as percentage of days when cough frequencies fall within that day’s 95% confidence interval. Overall Predictability was the mean of the 30 One Day Predictability percentages and ranged from 95% (best predictability) to 30% (least predictability). Conclusion There is substantial within-day and day-to-day variability for each subject with persistent cough recorded over 30 days. The clinical significance and the impact on the use of cough counts as a primary end-point of cough interventions of this variability need to be assessed.