Table 2:
Risk factors associated with venous and arterial thrombotic events among users of combined oral contraceptives
| Risk factor | Woman- years* | DVT and PE | TIA and CVA | ||
|---|---|---|---|---|---|
| No. (rate per 10 000 woman-years) | RR (95% CI) | No. (rate per 10 000 woman-years) | RR (95% CI) | ||
| Age, yr | |||||
| 12–19 | 97 161 | 34 (3.50) | Reference | 23 (2.37) | Reference |
| 20–24 | 307 850 | 139 (4.52) | 1.29 (0.89–1.88) | 100 (3.25) | 1.37 (1.06–1.78) |
| 25–29 | 193 552 | 115 (5.94) | 1.70 (1.16–2.49) | 84 (4.34) | 1.83 (1.41–2.39) |
| 30–34 | 101 578 | 73 (7.19) | 2.06 (1.37–3.09) | 78 (7.68) | 3.25 (2.48–4.25) |
| 35–39 | 63 020 | 70 (11.11) | 3.18 (2.11–4.79) | 84 (13.33) | 5.64 (4.32–7.36) |
| 40–44 | 39 549 | 62 (15.68) | 4.49 (2.96–6.83) | 72 (18.21) | 7.71 (5.88–10.10) |
| 45–50 | 17 016 | 25 (14.69) | 4.22 (2.52–7.07) | 58 (34.09) | 14.41 (10.91–19.05) |
| Diabetes mellitus | |||||
| No | 812 103 | 513 (6.32) | Reference | 482 (5.94) | Reference |
| Yes | 7 646 | 5 (6.54) | 1.04 (0.43–2.50) | 17 (22.23) | 3.75 (2.83–4.95) |
| Hyperlipidemia | |||||
| No | 758 616 | 466 (6.14) | Reference | 437 (5.76) | Reference |
| Yes | 61 133 | 52 (8.51) | 1.39 (1.04–1.85) | 62 (10.14) | 1.76 (1.51–2.06) |
| Hypertension | |||||
| No | 804 878 | 498 (6.19) | Reference | 453 (5.63) | Reference |
| Yes | 14 871 | 20 (13.45) | 2.19 (1.40–3.42) | 46 (30.93) | 5.50 (4.62–6.56) |
| Cancer | |||||
| No | 813 367 | 501 (6.16) | Reference | 491 (6.04) | Reference |
| Yes | 6 382 | 17 (26.64) | 4.33 (2.67–7.01) | 8 (12.54) | 2.09 (1.39–3.12) |
| Smoking | |||||
| No | 583 511 | 379 (6.50) | Reference | 353 (6.05) | Reference |
| Yes | 236 238 | 139 (5.88) | 0.91 (0.74–1.11) | 146 (6.18) | 1.02 (0.84–1.24) |
| Obesity | |||||
| No | 666 334 | 347 (5.21) | Reference | 331 (4.97) | Reference |
| Yes | 153 415 | 171 (11.15) | 2.15 (1.72–2.67) | 168 (10.95) | 2.21 (1.79–2.74) |
| Duration of use, mo | |||||
| ≤ 2 | 75 224 | 103 (13.69) | Reference | 97 (12.89) | Reference |
| 3–4 | 68 795 | 75 (10.90) | 0.80 (0.59–1.07) | 83 (12.06) | 0.94 (0.79–1.11) |
| 5–13 | 211 942 | 141 (6.65) | 0.49 (0.38–0.63) | 154 (7.27) | 0.56 (0.49–0.65) |
| ≥ 14 | 463 788 | 199 (4.29) | 0.31 (0.25–0.40) | 165 (3.56) | 0.28 (0.24–0.32) |
Note: CI = confidence interval, CVA = cerebrovascular accident, DVT = deep vein thrombosis, PE = pulmonary embolism, RR = rate ratio, TIA = transient ischemic attack.
*
Data on age were missing for 26 use episodes (23 woman-years of follow-up).