Short-term effects of airborne pollen on the risk of allergic rhinoconjunctivitis.

The authors carried out a pilot study in Clermont-Ferrand (France) over the period from 2000 to 2001 to analyze the short-term relationship between daily variations in rhinitis and allergic conjunctivitis and daily variations in pollen counts. Data from the ERASME database made it possible to identify all the individuals for whom at least one drug was prescribed to treat rhinitis or allergic conjunctivitis. Ten allergenic pollens were studied, and a Poisson regression model with penalized spline functions was used. A positive and significant association was found for pollens of Betula, Cupressaceae, Quercus, Fraxinus, and Poaceae. The relative risks varied between 1.3 (95% confidence interval [CI] = 1.0-1.5) and 1.2 (95% CI = 1.1-1.5) for an interquartile range increase of daily pollen counts of Cupressaceae (13 grains/m3) and of Betula (45 grains/m3), respectively. Further analyses, in particular, those using longer time series, are necessary to confirm these results.