Evidence Based Medicine
Indian Pediatrics 1999;36: 1286-1287
Caffeine and Asthma
Caffeine is found in tea, coffee, beverages and cola drinks. It belongs to a group of drugs called methylxanthines which also have theophylline. The proposed mechanism of action of methylxanthines in alleviating symp-toms of asthma is by inhibition of phospho-diesterases. Caffeine has been recommended as a remedy for asthma(1). A study by Pagano et al. in Italy found an inverse correlation between prevalence of asthma and amount of coffee consumed(2). A systemic review by Bare and Barley does suggest that caffeine leads to improvement in lung functions in asthmatic individuals(3).
The Search strategy used was within the Cochrane Airways Group Register of Asthma and Wheeze randomized controlled trials (RCTs). The bibliography of each RCT was searched for additional trials. Authors of identified RCTs were contacted for other published and unpublished studies.
Thirty-nine references were obtained from the literature search and independently assessed by the two reviewers. Full texts of potentially relevant trials were obtained. From these, six matched the inclusion criteria for this review. The two reviewers extracted data independently. Since lung function outcomes were measured at different times and following different doses of caffeine, data for each outcome were grouped according to three time frames: `short' - less than or equal to 2 hours; `medium'_greater than 2 hours and less than or equal to 4 hours; `long' _greater than 4 hours. Analysis were carried out using all caffeine doses and two subgroups based on the median dose: `low-dose_5 mg or less of caffeine per kg of body weight; `high' dose_greater than 5 mg of caffeine per kg of body weight.
The authors showed caffeine, even at a low dose, compared to placebo to significantly improve lung function, measured in terms of FEV1, FEF 25-75 and specific airway conductance for up to 2 hours post ingestion. This effect was sustained for FEF 25-75 for over 4 hours. Improvement was also seen in FEV1 upto this time, however this effect did not reach statistical significance. No data were available for specific airway conductance after 2 hours. Hence it is recommended that patients be advised to withhold caffeine for atleast four hours prior to lung function testing. Subjective patient benefits and clinical implications have not yet been thoroughly investigated. Caffeine improves airway function by a modest amount in asthmatic patients for upto four hours. Good news for coffee and cola drinkers!
1. Becker AB, Simons KJ, Gillipsie CA, Simons FE. The bronchodilator effect and pharmako-kinetics of caffeine in asthma. N Engl J Med 1984; 310: 743-746.
2. Pagano R, Negri E, Decarli A, Vecchia C. Coffee drinking and prevalence of bronchial asthma. Chest 1988; 94: 386-389.
3. Bara AL, Barley EA. The bronchodilator effect of caffeine in asthma. The Cochrane library, 1998 Issue 2, Update Software, Oxford, UK.