Table 1

Characteristics of cases and controls*

(n=43 023)
Age at entry (SD)‡
 (median, (IQR))
28.0 (10.3)
(28.6 (18.7–37.3))
28.1 (10.3)
(28.6 (18.7–37.2))
Age at index date (SD)‡
 (median, (IQR))
32.6 (11.0)
(33.6 (23.3–42.1))
32.6 (11.0)
(33.5 (23.2–42.1))
% Female‡63.863.8
Variables ascertained in the 12-month baseline period
 Number of asthma-related hospitalisations in baseline‡0.200.05
Variables ascertained in the 12-month period prior to the index date
 Number of dispensations of short-acting β agonists7.346.43
 Number of dispensations of oral or nebulised β agonists0.480.31
 Number of dispensations of oral or injected corticosteroids1.381.05
 Number of asthma-related outpatient services§8.185.45
 Number of dispensations of other asthma-related medications9.738.49
 Charlson comorbidity index0.960.85
 Number of non-asthma-related hospitalisations1.151.07
 Number of non-asthma-related outpatient services§42.2938.16
 Number of dispensations of medications of all type26.3120.78
  • †All statistics for controls are weighted by the inverse of the number of controls in each stratum. Matching was complete on all 6 asthma-related variables for 87.5% of controls, and on at least 5 variables in 96.8% of controls.

  • ‡Variable is used for matching.

  • §An outpatient service is activity provided by a health practitioner that can be reimbursed by the government. A visit to a physician often results in billing for several services (see BC MSP Payment Schedule at for details).