THUNDERSTORM ASSOCIATED ASTHMA - A DETAILED ANALYSIS OF ENVIRONMENTAL-FACTORS

Objectives-To seek meteorological factors, pollutants or pollen, and a n asthma epidemic which occurred in London on 24 and 25 June 1994 afte r a thunderstorm. Design-Retrospective study of patients' accident and emergency department records, with bivariate and multivariate analysi s of environmental factors and data collection for the two months surr ounding the epidemic. Setting-The accident and emergency department of St Mary's Hospital in west central London. Subjects-148 patients pres enting with asthma between 1 June and 31 July 1994, of whom 40 present ed in the 24 hours after the storm. Results-The asthma epidemic was si gnificantly associated with a drop in air temperature six hours previo usly and a high grass pollen concentration nine hours previously. Non- epidemic asthma was significantly associated with lightning strikes, i ncrease in humidity or sulphur dioxide concentration, a drop in temper ature or high rainfall the previous day, and a decrease in maximum air pressure or changes in grass pollen counts over the previous two days . Conclusions-New episodes of asthma during the epidemic on 24 and 25 June 1994 were associated with a fall in air temperature and a rise in grass pollen concentration. Non-epidemic asthma was significantly ass ociated with a greater number of environmental changes. This may indic ate that the patients with thunderstorm associated asthma were a separ ate population, sensitive to different environmental stimuli.