Coffee drinking and prevalence of bronchial asthma.

The relationship between coffee consumption and the prevalence of bronchial asthma has been evaluated using data from the 1983 Italian National Health Survey, based on 72,284 individuals aged over 15 years randomly selected within strata of geographic area, size of the place of residence and of the household in order to be representative of the whole Italian population. The prevalence of bronchial asthma was inversely related with the level of coffee intake. Compared with subjects who did not drink coffee, the age- and sex-adjusted relative risks were 0.95 for one cup, 0.77 for two and 0.72 for three or more cups per day. This inverse relation was of comparable magnitude at younger and older ages, not explainable through selection, since the sample was representative of the general Italian population and the participation rate was 93.4 percent, or through confounding by several identified potential distorting factors. Thus, the results of this survey provide epidemiologic confirmation of previous clinical observations that caffeine intake has a bronchodilator effect in asthma, and indirectly suggest that long-term moderate coffee consumption may not only reduce symptoms, but also prevent the clinical manifestation of bronchial asthma. An alternative explanation of these findings is that subjects receiving treatment for asthma might tend to reduce their coffee consumption, in consequence of the side effects shared by sympathomimetics, theophylline and caffeine. Thus, further studies taking simultaneously into account methylxanthine intake from beverages and drug treatments are required before considering causal the apparent protection which emerged.