" LIVING WITH ASTHMA "

Asthma & coffee

Theophylline, a bronchodilator, is a drug frequently used in the treatment of asthma. Since caffeine is chemically similar to theophylline, could caffeine also work to dilate the airway passages in the lung?

The study: Researchers looked at all the published clinical trials studying the use of oral caffeine to treat asthma. They analysed only clinical trials that compared patients taking oral caffeine to those taking a placebo and evaluated the effect on lung function. Two studies used a 'low' caffeine dose of 5 mg per kg of body weight and four studies used a 'high' dose of 6-10 mg per kg of body weight. The average amount of caffeine per cup of coffee is between 30mg and 150 mg.

The results: Six methodologically sound trials with a total of 55 patients were included in this review. All found that oral caffeine improved lung function measured by forced expiratory volume in 1 second (FEV1) and peak expiratory flow (PEF). FEV1 showed a small improvement up to two hours after caffeine. Mid-expiratory flow rates also showed a small improvement with caffeine and this was sustained for up to four hours. Adverse effects observed in patients taking high doses of caffeine were tremor, nervousness, agitation and changes in heart rate and blood pressure.

The conclusion: The authors of this review of the literature found that caffeine was mildly effective in improving airway function. Results were so consistent that they felt asthmatics should avoid caffeine for 4 hours before any lung function test. However, they conclude that there is not enough evidence to determine if this improvement in lung function will reflect in improvements of asthma symptoms and quality of life.