Characteristics of cases and controls*
| Cases (n=3319) | 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‡ | 63.8 | 63.8 |
| Variables ascertained in the 12-month baseline period | ||
| Number of asthma-related hospitalisations in baseline‡ | 0.20 | 0.05 |
| Variables ascertained in the 12-month period prior to the index date | ||
| Number of dispensations of short-acting β agonists | 7.34 | 6.43 |
| Number of dispensations of oral or nebulised β agonists | 0.48 | 0.31 |
| Number of dispensations of oral or injected corticosteroids | 1.38 | 1.05 |
| Number of asthma-related outpatient services§ | 8.18 | 5.45 |
| Number of dispensations of other asthma-related medications | 9.73 | 8.49 |
| Charlson comorbidity index | 0.96 | 0.85 |
| Number of non-asthma-related hospitalisations | 1.15 | 1.07 |
| Number of non-asthma-related outpatient services§ | 42.29 | 38.16 |
| Number of dispensations of medications of all type | 26.31 | 20.78 |
†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 http://www.health.gov.bc.ca/msp/infoprac/physbilling/payschedule/index.html for details).