title: Does diurnal variation in cough reflex testing exist in healthy young adults?
abstract: The aim of this study was to investigate whether diurnal variation in cough reflex sensitivity exists in healthy young adults when a tidal-breathing method is used. Fifty-three participants (19-37 years) underwent cough reflex testing on two occasions: once in the morning (between 9 am - midday) and once in the afternoon (between 2-5 pm). The order of testing was counter-balanced. Within each assessment, participants inhaled successively higher citric acid concentrations via a facemask, with saline solution randomly interspersed to control for a placebo response. The lowest concentration that elicited a reflexive cough response was recorded. Morning cough thresholds (mean=0.6mol/L) were not different from afternoon cough thresholds (mean=0.6mol/L), p=0.16, T=101, r=-0.14. We found no evidence of diurnal variability in cough reflex testing. There was, however, an order effect irrespective of time of day, confirming that healthy participants are able to volitionally modulate their cough response.
authors.affiliation: Department of Communication Disorders, University of Canterbury Rose Centre for Stroke Recovery and Research at St George's Medical Centre, Leinster Chambers, Level One, 249 Papanui Road, Christchurch 8014, New Zealand. Electronic address: sep2180@tc.columbia.edu.
authors.forename: Sarah
authors.initials: S
authors.lastname: Perry
authors.affiliation: Department of Communication Disorders, University of Canterbury Rose Centre for Stroke Recovery and Research at St George's Medical Centre, Leinster Chambers, Level One, 249 Papanui Road, Christchurch 8014, New Zealand. Electronic address: maggie-lee.huckabee@canterbury.ac.nz.
authors.forename: Maggie-Lee
authors.initials: ML
authors.lastname: Huckabee
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D003371:Cough / Q000503:physiopathology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D012018:Reflex / Q000502:physiology*; D012119:Respiration; D013990:Tidal Volume / Q000502:physiology; D055815:Young Adult
keywords: Citric acid; Cough reflex; Diurnal