Patterns of increasing β-agonist use and the risk of fatal or near-fatal asthma

Patterns of increasing β-agonist use and the risk of fatal or near-fatal asthma. ERS Journals Ltd 1994. ABSTRACT: The association between the use of inhaled β-agonists by metereddose inhaler and the risk of fatal or near-fatal asthma has been demonstrated. It shows that asthmatics who use one canister of β-agonist per month more than the number used by other similar asthmatics have twice the risk of fatal or near-fatal asthma. The present investigation assesses the magnitude of this excess risk when an asthmatic increases his/her own monthly use of inhaled β-agonists over time. From a previous nested case-control study of 129 deaths and near-deaths from asthma (cases) and 655 controls from a cohort of 12,301 asthmatics, the subset using at least 12 inhalers during the 12 month study period was identified (97 cases and 258 controls). A profile score, ranging 0–11, was formed to quantify the patterns of β-agonist use over time for each subject, covering the entire spectrum extending from decreasing to increasing use. The relative risk was 15.2 (95% confidence interval (CI) 2.4–96.2) per unit increase of the profile score in subjects with a pattern of increasing β-agonist use (profile score of 6.5 or more), but this relative risk was only 1.5 (95% CI 0.8–2.6) per unit when the profile score was less than 6.5 (non-increasing use). This relative risk was independent of the risk associated with the total quantity of β-agonist use in the 12 month period, which remained around 1.6 (95% CI 1.3–2.0) per inhaler per month. We conclude that above and beyond the quantity of β-agonist used during a one year period, a pattern of increasing use of β-agonist inhalers over that period is a major predictive factor of unfavourable outcomes in asthma. Any trend, over a six month span, of a doubling in the monthly use of β-agonists, or, alternatively, of an increase by one canister in this monthly use, should be regarded as a serious warning sign of an impending life-threatening attack of asthma. Eur Respir J., 1994, 1602–1609. *Dept of Epidemiology and Biostatistics and the Pharmacoepidemiology Research Unit, and †Dept of Medicine, Montreal General Hospital, McGill University, Montreal, Quebec, Canada.