No large study has described seasonal variation in asthma attacks in population based asthmatics in whom sensitisation to allergen has been measured.
2,637 young adults with asthma living in 15 countries reported months in which they usually had attacks of asthma and had skin prick tests performed. Differences in seasonal patterns by sensitisation status were assessed using generalised estimating equations.
Most young adults with asthma reported periods of the year when their asthma attacks were more common (range 47% in Sweden to 86% in Spain). Seasonal variation in asthma was not modified by sensitisation to house dust mite or cat. Asthmatics sensitised to grass, birch and Alternaria had different seasonal patterns to those not sensitised to each allergen, with some geographical variation. In Southern Europe, those sensitised to grass were more likely to report attacks occurred in spring/summer than in winter (ORMarch/April=2.60; 95%CI 1.70–3.97; ORMay/June=4.43; 95%CI 2.34–8.39) and smaller later peaks were observed in Northern Europe (ORMay/June=1.25; 95%CI 0.60–2.64; ORJuly/August1.66; 95%CI 0.89–3.10). Asthmatics reporting hayfever but who were not sensitised to grass showed no seasonal variations.
Seasonal variation in asthma attacks in young adults is common and is different depending on sensitisation to outdoor, but not indoor, allergens.
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