Table 1.
Characteristics of breast cancer cases and age-matched controls.
| Characteristic | Cases N = 2129 | (%) | Controls N = 21297 | (%) | Unadjusted ORa |
|---|---|---|---|---|---|
| n | n | (95% CI) | |||
| Age (years) | |||||
| Mean (SD) | 60.4 | (11.4) | 60.3 | (11.4) | |
| Age categories | |||||
| <40 | 57 | (2.7) | 570 | (2.7) | 1.00 (Reference) |
| 40–55 | 685 | (32.2) | 6972 | (32.7) | 0.98 (0.74, 1.31) |
| >55 | 1387 | (65.2) | 13755 | (64.6) | 1.01 (0.76, 1.33) |
| Follow-up (years)b | |||||
| Mean (SD) | 28.9 | (3.5) | 28.8 | (3.7) | 1.01 (0.99, 1.02) |
| Median (range) | 30.0 | (10, 32) | 30.0 | (10.32) | |
| Marital statusc | |||||
| Other (widowed, separated, divorced) | 393 | (18.5) | 4386 | (20.6) | 1.00 (Reference) |
| Single | 139 | (6.5) | 1421 | (6.7) | 1.09 (0.89, 1.34) |
| Married | 1597 | (75.0) | 15490 | (72.7) | 1.15 (1.03, 1.29) |
| Income support statusd | |||||
| No income support | 1542 | (72.4) | 15049 | (70.7) | 1.00 (Reference) |
| Low income support | 507 | (23.8) | 5375 | (25.2) | 0.92 (0.83, 1.02) |
| High income support | 80 | (3.8) | 873 | (4.1) | 0.89 (0.71, 1.13) |
| Place of residencee | |||||
| Urban | 911 | (42.8) | 8837 | (41.5) | 1.00 (Reference) |
| Rural | 1218 | (57.2) | 12460 | (58.5) | 0.95 (0.87, 1.04) |
| Oral contraceptive (OC) usef | |||||
| None or light use (<12 prescriptions) | 1620 | (76.1) | 16775 | (78.8) | 1.00 (Reference) |
| Heavy use (≥12) | 509 | (23.9) | 4522 | (21.2) | 1.17 (1.05, 1.29) |
| Hormone therapy (HT) usef | |||||
| None or light use (<12 prescriptions) | 1503 | (70.6) | 15542 | (73.0) | 1.00 (Reference) |
| Heavy use (≥12) | 626 | (29.4) | 5755 | (27.0) | 1.13 (1.02, 1.24) |
OR, odds ratio(s); CI, confidence intervals.
aFrequency-matched on age in 5-year groups but not adjusted for the influence of other risk factors.
bFollow-up: number of years eligible to receive outpatient prescription drug benefits in Saskatchewan.
cMarital status: attributed to the marital state 6 years prior to index date.
dIncome support status: based on yearly demographic data and assigned to one of 3 categories based on the greatest proportion of time having received income support: i.e., no income support, ≤50% of time receiving income support = low income support, and >50% of time receiving income support = high income support.
ePlace of residence: based on yearly demographic data and assigned based on the greatest proportion of time spent in a given residence state: i.e., ≤50% of time in urban location (population > 100,000) = rural residence status and >50% of time as urban = urban residence status.
fOC and HT use: defined as total number of prescriptions 2 or more years prior to index date. These drugs are typically dispensed as a 2-month supply; therefore, in most cases, 12 prescriptions would correspond to a 2-year supply. All oral and injectable contraceptives were included as were all hormone therapy formulations except vaginal creams and rings.
Percentages may not add up to 100% due to rounding.