Chronic cough associated with gastro oesophageal reflux is a common but frequently under diagnosed condition. This is due to the ‘atypical’ presentation with symptoms of non-peptic, extra-oesophageal origin. To define this syndrome a variety of questionnaires such as the Reflux Symptom Index have been developed. In this study we have used the HARQ, a questionnaire developed specifically to quantify the symptoms of airway reflux underlying cough hypersensitivity. Our patients all exhibited HARQ scores above the cut off of 13/70 required to diagnose airway reflux and represent a distinctive population of patients with reflux induced cough hypersensitivity syndrome .
There is a dearth of treatment options available to patients with airway reflux. Pharmacotherapy with conventional acid suppression has recently been shown to be no more effective than placebo  presumably because of the non-peptic nature of the tussive stimulus. Pro-motility agents such as metoclopramide, domperidone and macrolides have been advocated, but there is a lack of randomised control trials supporting their use. The only evidence based therapy is oral opiates , which do not treat reflux but suppresses cough reflex hypersensitivity centrally.
Non-pharmacological treatment has been shown to be effective. Specific cough related speech therapy has been demonstrated to diminish cough reflex sensitivity and improve quality of life . We had previously observed a significant relationship between obesity and chronic cough in a survey of the general population . This observation is mirrored in studies showing an increase of obesity related GORD . This led us to hypothesize that weight reduction may offer a further non-pharmacological treatment option in obese chronic cough patients.
We have tested this hypothesis by comparing two dietary measures that may aid resolution of airway reflux. The traditional ‘textbook’ GORD anti-reflux diet was compared to an EP diet, targeting weight control. We showed no difference between these two strategies, both of which produced weight loss and a reduction in cough score. Surprisingly, percentage weight loss was slightly greater in the traditional ‘textbook’ GORD anti-reflux diet group, and there appears to be little evidence that dietary intervention needs to follow a restriction of foods of any particular ‘refluxogenic’ type for improvement to be manifest.
Analyses of the food diaries at baseline showed current high intakes of calories and fat had an adverse effect on cough quality of life suggesting that this may contribute to chronic cough. Other studies in GORD have demonstrated an association of a high fat intake and the occurrence of reflux [11, 12]. Moreover, weight loss has been shown to improve pH profiles and symptoms in GORD patients . An alternative mechanism to explain our observation may be that the high fat and calorie intake leads to weight gain which in turn causes reflux. This is supported by research suggesting that reflux is more prevalent in the overweight and obese population rather than the lean [5–8].
Since there was no non-intervention group in our study it is impossible to say whether the dietary measures directly contributed to the improvement in cough quality of life. Chronic cough may follow a waxing and waning course  and it is possible that the improvement in cough score may be explicable by regression to the mean from the pre study baseline. The effectiveness of a dietary intervention on cough however, with all of the patients who completed the study showing a greater than MCS improvement in cough quality of life score, would tend to suggest a clinically important effect of this intervention.
In interpreting our observations one needs to take into account some limitations in our study. Firstly, recruitment to the study was slower than expected due to 21 patients who declined to take part from the outset despite encouragement from the medical team. Patients in the Hull Cough Clinic often request advice on lifestyle modification and it was perhaps surprising that these proposals were rejected when offered. There are many factors that contribute to a person’s motivation to lose weight which include their readiness for change and barriers to change such as how diet and exercise affects health. As our study required that the patient to be reviewed monthly over a seven month period, study duration may have been a contributing factor. An individual’s perceived lack of time is one of the barriers to change . NICE Guidelines on Obesity however, recommends that ‘regular, non-discriminatory long term follow up by a trained professional should be offered’ . It is possible that these recommendations may hamper rather than aid compliance. Secondly, as with many studies into the effect of lifestyle change, this study could not use a blinded methodology. As a consequence all patients recruited were aware of our hypothesis that weight loss would contribute to a reduction in reflux cough. Thirteen of the recruited subjects dropped out of the study, with 8 subjects providing no reason. A number who completed the study stated that they were disappointed to be allocated into what was perceived as the control group, i.e. the traditional anti-reflux diet. Moreover, the overall number of patients who completed the study was small. Thirdly, we did not perform objective assessments of GORD since existing techniques are poorly correlated with non acid reflux as determined by symptom assessment. There is an urgent need for such measurements to be developed. Additionally we did not study objective parameters of cough and we acknowledge this as a weakness of the study. The above may have diminished our understanding of the pathobiological basis of the cough reduction seen. In particular, Obstructive Sleep Apnoea (OSA) in obese subjects can rarely precipitate cough , and maybe improved by weight reduction. While we have shown statistical significance effects however, studies on larger numbers of patients will be required to draw definitive conclusions.