Introduction Objective cough monitoring is a useful tool to investigate patterns of cough frequency and to evaluate novel cough treatments. The VitaloJAKTM (Vitalograph Ltd, UK) ambulatory cough monitor is a validated semi-automated system for the quantification of cough over 24 hours. Objective cough rates have yet to be quantified in large groups of healthy controls and the influences of subject factors are unclear.
Objective To assess objective cough frequency in a large group of healthy adults across a range of ages.
Method Objective 24 hour cough monitoring was performed using the VitaloJAKTM in adult healthy volunteers; those with a smoking history of >20 pack years and <6 months abstinence were excluded. The recordings were compressed using custom-written software and cough counted manually by trained cough counters and the daytime, night-time and total cough rates calculated. Daytime and total cough rates were log transformed for analysis. Independent t-tests (daytime and total) and Mann-Whitney U test (night-time) assessed the effect of gender and previous smoking. Spearmans correlation coefficients evaluated the relationships between cough frequency, age, BMI, and pulmonary function.
Results Sixty healthy volunteers were recruited; 27 (45%) males, median age 40 yrs (range 20–74), median FEV1 103.0% predicted (81–141), median FVC 105.5% predicted (82–151), median BMI 24.6 kg/m2 (16.8–39.8), 48 (80%) of subjects had never smoked, median smoking history in the ex-smokers 2.9 (0.1–17) pack years. Median (IQR) 24 h cough rate was 0.17 c/h (0.05–0.87) with daytime rate of 0.26 c/h (0.63–1.35) and night-time rate of 0.00 c/h (0.00–0.12). Males coughed significantly more than females over 24hours [median 0.42 c/h (IQR 0.13–1.21) vs. 0.13 c/h (0.04–0.59), p = 0.038] and during the day [0.37 c/h (0.11–1.42) vs. 0.19 c/h (0.0–0.91), p = 0.036], but not during the night (p = 0.852). Cough frequency was not significantly correlated with age, BMI, FEV1 or FVC. Cough frequency was no different between never and ex-smokers for daytime or 24 h (p = 0.46 and p = 0.20) but overnight was slightly lower for ex- than never smokers [median 0.00 c/h (0.00–0.09) vs. 0.12 c/h (0.0–0.64), p = 0.037].
Conclusions In healthy adults, spontaneous cough frequency is unaffected by age, BMI, and pulmonary function. Interestingly, males coughed more frequently than females, in contrast to our current knowledge of gender differences in cough reflex sensitivity.