Short-term effect of pollen exposure on antiallergic drug consumption

Several studies have investigated the association between pollen exposure and asthma emergency admissions, but only 2 have investigated the effect of airborne allergens on consultations for rhinitis or conjunctivitis and none has used drug consumption as the health indicator.

To analyze the short-term association between pollen exposure and antiallergic drug consumption in the urban area of Clermont-Ferrand, France, taking into account the potentially confounding effect of air pollution and meteorological factors.

We used the French health insurance database to select all individuals from the Clermont-Ferrand urban area having benefited from reimbursement for antiallergic treatment from January 1, 2000, through December 31, 2001, and from January 1, 2003, through December 31, 2004. An episode of treated allergic rhinitis, rhinosinusitus, or conjunctivitis (ARC) was defined as the association of an oral antihistamine and a local antiallergic drug on the same prescription. The relations between daily changes in pollen concentrations and daily changes in the number of treated ARC cases were analyzed using a Poisson regression model with penalized spline functions.

The risk of treated ARC associated with an interquartile increase in pollen concentration increased significantly for Poaceae (5%, P < .001), Fraxinus (7%, P < .001), Betula (7%, P < .001), and Corylus (2%, P < .02). This increase was significant in all age groups for Poaceae and Fraxinus pollen and in people younger than 65 years for Betula pollen. The effect was mainly concentrated on the present day, except for Poaceae pollens, for which the risk remained significantly (P < .001) increased until 3 days lag time.

This study showed a significant increase in treated ARC cases related to Poaceae, Fraxinus, and Betula. Specific risks are difficult to evaluate for species that share the same pollination period. Time-series studies based on drug consumption are useful to highlight and to supervise pollen-related diseases requiring ambulatory care.