Sex differences and predictors of objective cough frequency in chronic cough.

BACKGROUND: Women are consistently over-represented in specialist cough clinics and known to have a more sensitive cough reflex than men. Whether female sex and other patient characteristics are associated with higher cough rates is not known. A study was conducted to determine the predictors of objective cough frequency in patients presenting to a tertiary referral clinic with chronic cough. METHODS: 100 subjects (65 women) of mean (SD) age 55.8 (11.0) years and median cough duration 4 years (IQR 2.0-10.0) with unexplained chronic cough completed flow-volume loops (mean (SD) forced expiratory volume in 1 s 103 (15.2)% predicted; forced expiratory flow (FEF(50)) 68.8 (24.1)% predicted), methacholine challenge (42% positive), citric acid cough reflex sensitivity (C5; 0.12 M (IQR 0.06-0.50)) and the Leicester Cough Questionnaire. 24-h ambulatory cough monitoring was performed in 86 subjects; manually counted coughs were quantified as the number of explosive cough sounds per hour. RESULTS: Women coughed significantly more than men (geometric mean 16.6 coughs/h (95% CI 13.1 to 21.0) vs 9.4 coughs/h (95% CI 6.4 to 13.9), p = 0.01)). The cough reflex was also more sensitive in women than in men (median logC5 -0.9 M vs -0.6 M, p = 0.002), but cough-related quality of life was similar in women and men (12.0 (3.6) and 12.2 (3.2), respectively, p = 0.76). Linear regression analysis showed that 38.6% of the variation in cough rate was predicted by sex (p = 0.01), logC5 (p<0.001) and age (p = 0.002) but not lung function or bronchial hyper-reactivity. CONCLUSIONS: Ambulatory objective cough monitoring provides novel insights into factors modulating chronic cough. These findings suggest that effects of sex and age must be taken into account in the study of cough and when designing clinical trials testing novel antitussive agents.

How to quantify coughing: correlations with quality of life in chronic cough.

Different methods are used for quantifying coughing in sound recordings, but as yet no method has been shown to be more valid than any other. In the present study, the relationships between three different units of cough were examined and their ability to predict subjective ratings of cough and cough-related quality of life were evaluated. In total, 70 subjects (mean+/-SD age 55+/-11.7 yrs, 51 (73%) females) with chronic unexplained cough (median duration 4.8 yrs, interquartile range 2.5-10.1 yrs) performed fully ambulatory 24-h sound recordings, which were manually counted by trained observers and quantified by 1) explosive phases, 2) cough seconds and 3) cough epochs. Subjects also completed cough visual analogue scales (VAS) and the Leicester Cough Questionnaire (LCQ). All units of cough were strongly correlated; explosive phases and cough seconds correlated slightly more strongly than cough seconds with cough epochs or explosive phases with cough epochs. LCQ scores correlated moderately with explosive phases and seconds; epochs correlated slightly less well. Cough VAS scores showed a similar pattern. Explosive phases and seconds are interchangeable units of cough, moderately related to subjective measures and cough-related quality of life; epochs are a less satisfactory alternative.

Airway abnormalities at flexible bronchoscopy in patients with chronic cough.

The algorithms utilised in the diagnosis of chronic cough advocate sequential investigations and treatment trials for asthma-like syndromes, post-nasal drip and gastro-oesophageal reflux disease; however, the role of bronchoscopy is unclear. In the present authors' specialist clinic (North West Lung Centre Cough Clinic, Manchester, UK), flexible bronchoscopy is included in the diagnostic work-up of patients with chronic unexplained cough. In a retrospective review, the authors report on their experiences. Over an 18-month period, patients followed a diagnostic algorithm that included: chest radiography; pulmonary function; methacholine challenge; ear, nose and throat examination; and empirical reflux treatment. Where diagnosis remained elusive, bronchoscopy was performed. A total of 82 bronchoscopies were carried out for the sole indication of chronic cough. Patient age (mean+/-SD) was 54.9+/-11.22 yrs, with a median (range) cough duration of 5 (0.5-30) yrs. In nine (11%) subjects, a diagnosis was made on inspection or biopsy. These included seven cases of tracheobronchopathia osteochondroplastica (TPO), one case of elongated uvula and one case of endobronchial amyloidosis. All TPO patients had early changes, with a typical nodular appearance to the tracheal cartilage, without significant airway obstruction. These subtle changes could not have been predicted from less invasive procedures and would have been missed without bronchoscopy. Flexible bronchoscopy is indicated in persistent unexplained cough and may reveal contributing pathology.