Table 1.
Characteristics of cases and controls
| Cases (n = 1262) | Controls (n = 12,620) | OR | (95% CI) | |
|---|---|---|---|---|
| Age, n (%) | ||||
| ≤ 50 | 234 (18.5) | 2891 (22.9) | 1.00 | 1 |
| 51–60 | 256 (20.3) | 2919 (23.1) | 1.08 | (0.90–1.30) |
| 61–70 | 310 (24.6) | 4155 (32.9) | 0.92 | (0.77–1.10) |
| 71–80 | 256 (20.3) | 1874 (14.8) | 1.70 | (1.41–2.04) |
| > 80 | 206 (16.3) | 781 (6.2) | 3.32 | (2.71–4.08) |
| Health care region | ||||
| Stockholm/Gotland | 531 (42.1) | 5908 (46.8) | 1.00 | 1 |
| Uppsala/Örebro | 529 (41.9) | 5005 (39.7) | 1.18 | (1.04–1.33) |
| Northern | 202 (16.0) | 1707 (13.5) | 1.32 | (1.11–1.56) |
| T stage | ||||
| T1 | 220 (17.4) | 6821 (54.0) | 1.00 | 1 |
| T2 | 772 (61.2) | 4961 (39.3) | 4.90 | (4.20–5.72) |
| T3 | 190 (15.1) | 648 (5.1) | 9.07 | (7.35–11.2) |
| T4 | 62 (4.9) | 123 (1.0) | 15.92 | (11.4–22.3) |
| TX | 18 (1.4) | 67 (0.5) | 8.37 | (4.88–14.34) |
| N stage | ||||
| N0 | 414 (32.8) | 8297 (65.7) | 1.00 | 1 |
| N + | 823 (65.2) | 4280 (33.9) | 3.86 | (3.41–4.37) |
| Missing | 25 (2.0) | 43 (0.3) | 12.39 | (7.39–20.77) |
| Chemotherapy | ||||
| No chemotherapy | 584 (46.3) | 7855 (62.2) | 1.00 | 1 |
| Chemotherapy | 678 (53.7) | 4765 (37.8) | 1.93 | (1.72–2.17) |
| Tamoxifen use | ||||
| No tamoxifen | 363 (28.8) | 3316 (26.3) | 1.00 | 1 |
| 0–2 years | 503 (39.9) | 3354 (26.6) | 1.41 | (1.22–1.63) |
| 2–5 years | 320 (25.4) | 3879 (30.7) | 0.74 | (0.63–0.86) |
| 5 + years | 76 (6.0) | 2071 (16.4) | 0.30 | (0.23–0.39) |
| AI use | ||||
| No AI | 137 (10.9) | 5549 (44.0) | 1.00 | 1 |
| 0–2 years | 506 (40.1) | 2777 (22.0) | 7.51 | (6.17–9.14) |
| 2–5 years | 463 (36.7) | 3122 (24.7) | 6.18 | (5.06–7.53) |
| 5 + years | 156 (12.4) | 1172 (9.3) | 5.56 | (4.34–7.11) |
| Marital status | ||||
| Married | 557 (44.1) | 6485 (51.4) | 1.00 | 1 |
| Not married | 705 (55.9) | 6135 (48.6) | 1.34 | (1.19–1.50) |
| Family income | ||||
| Low | 571 (45.2) | 4017 (31.8) | 1.00 | 1 |
| Intermediate | 397 (31.5) | 4189 (33.2) | 0.66 | (0.58–0.76) |
| High | 278 (22.0) | 4304 (34.1) | 0.45 | (0.39–0.52) |
| Missing | 16 (1.3) | 110 (0.9) | 1.01 | (0.60–1.72) |
| Educational level | ||||
| Low | 403 (31.9) | 2897 (23.0) | 1.00 | 1 |
| Intermediate | 496 (39.3) | 5178 (41.0) | 0.69 | (0.60–0.79) |
| High | 363 (28.8) | 4545 (36.0) | 0.57 | (0.49–0.67) |
| Drug Comorbidity Index (quartile) | ||||
| 1 (lowest) | 173 (13.7) | 3299 (26.1) | 1.00 | 1 |
| 2 | 244 (19.3) | 3225 (25.6) | 1.44 | (1.18–1.76) |
| 3 | 365 (28.9) | 3105 (24.6) | 2.23 | (1.85–2.69) |
| 4 (highest) | 480 (38.0) | 2991 (23.7) | 3.06 | (2.55–3.66) |
| Charlson comorbidity index | ||||
| 0 | 937 (74.2) | 10,344 (82.0) | 1.00 | 1 |
| 1 | 170 (13.5) | 1220 (9.7) | 1.53 | (1.29–1.82) |
| 2 + | 155 (12.3) | 1056 (8.4) | 1.62 | (1.35–1.94) |
| History of estrogen therapy | ||||
| No history | 1057 (83.8) | 10,466 (82.9) | 1.00 | 1 |
| History of estrogen therapy | 205 (16.2) | 2154 (17.1) | 0.94 | (0.81–1.10) |