Table 1.
Characteristics of the multiple sclerosis (MS) cases and controls in the administrative and clinical cohorts at the index date in British Columbia, Canada.
| Administrative cohort | Clinical cohort | |||
|---|---|---|---|---|
| Characteristics |
MS cases, N = 6,863 |
Controls, N = 31,865c |
MS cases, N = 966 |
Controls, N = 4,534c |
| Females, N (%) | 5,039 (73.4) | 23,311 (73.2) | 728 (75.4) | 3,398 (74.9) |
| Age at index date (years) | ||||
| < 30 | 859 (12.5) | 4,080 (12.8) | 232 (24.0) | 1,082 (23.9) |
| 30 to < 50 | 3,827 (55.8) | 17,899 (56.2) | 639 (66.1) | 2,992 (66.0) |
| ≥50 | 2,177 (31.7) | 9,886 (31.0) | 95 (9.8) | 460 (10.1) |
| Mean (SD) | 44.4 (13.5) | 44.2 (13.4) | 37.0 (10.2) | 36.9 (10.1) |
| Index year, N (%) | ||||
| 1996–2000 | 2,001 (29.2) | 9,216 (28.9) | 589 (61.0) | 2,764 (61.0) |
| 2001–2005 | 2,149 (31.3) | 9,914 (31.1) | 344 (35.6) | 1,618 (35.7) |
| 2006–2008a/2010b | 2,078 (30.3) | 9,736 (30.6) | 33 (3.42) | 152 (3.35) |
| 2011–2013 | 235 (9.3) | 2,999 (9.4) | ||
| SES at index date, N (%) | ||||
| 1 (lowest quintile) |
1,184 (17.3) | 5,476 (17.2) | 145 (15.0) | 763 (16.8) |
| 2 | 1,286 (18.7) | 5,950 (18.7) | 180 (18.6) | 812 (17.9) |
| 3 | 1,413 (20.6) | 6,329 (19.9) | 204 (21.1) | 895 (19.7) |
| 4 | 1,465 (21.3) | 6,826 (21.4) | 194 (20.1) | 962 (21.2) |
| 5 (highest quintile) |
1,365 (19.9) | 6,591 (20.7) | 210 (21.7) | 952 (21.0) |
| Missing | 150 (2.2) | 693 (2.2) | 33 (3.4) | 150 (3.3) |
aThe index year category for the clinical cohort was 2006–2008.
bThe index year category for the administrative cohort was 2006–2010.
cFive controls matching on sex, birth year and postal code were not available for each MS case. Therefore, some MS cases were matched to fewer than 5 controls.
SES, socio-economic status.