Mild cool air--a risk factor for asthma exacerbations: results of a retrospective study

Worldwide incidence of bronchial asthma is on rise. Infections either viral or bacterial and various environmental factors are considered as major risk factors for exacerbations in various studies. Despite of awareness and preventive strategies to risk factors, exacerbations largely remain uncontrolled, therefore the study was planned to review the existing risk factors and to find out some other risk factor/factors which could help us in understanding the other causes of exacerbations.

The study was done in Ajmer, the central part of Rajasthan state, India, at Mittal Hospital & Research Centre and J. L. N. Medical college hospital by collecting data for the period of four years (January 2006 - December 2009). Monthly record of 300 regular cases of bronchial asthma was taken. This record included symptoms, history of exposure to various risk factors, and PEFR. Environmental data was also collected. On the basis of record monthly attack rate was calculated. RESULTS/OBSERVATIONS: Maximum attack rate (> 90%) was found in October, November (early winter) and February and March (spring) during all the four years studied except in October 2009. A common precipitant present during these months was mild cool air (environmental temperature of 23-27 degrees c). Attack rate was very less above and below of this temperature. No clear association was present with any other known precipitants.

It is concluded that inhalation of mild coolair (23-27 degrees c) may be an important risk factor besides other risk factors for asthma exacerbation.