Table 2.
Incidence rates per 10,000 person-years and incidence rate ratios of venous thrombosis in starters vs switchers, overall and per combined oral contraceptive generation in the Netherlands.
| Starters |
||||||
|---|---|---|---|---|---|---|
| N of starters (%) | N of VT events | Person-years | IR per 10,000 person-years (95% CI) | IRR (95% CI) switchers vs starters (ref.) | aIRRa (95% CI) switchers vs starters (ref.) |
|
| Total, N | 5,053,024 | 2005 | 3,361,434 | 5.96 (5.70-6.23) | Reference | Reference |
| Second-generation | 3,769,077 (74.59) | 1375 | 2,543,654 | 5.41 (5.12-5.69) | Reference | Reference |
| Third-generation | 556,017 (11.00) | 345 | 387,240 | 8.91 (7.97-9.85) | Reference | Reference |
| Fourth-generation | 727,930 (14.41) | 285 | 430,539 | 6.62 (5.85-7.39) | Reference | Reference |
| N of switchers (%) Switchers | ||||||
| Total, N | 153,797 | 70 | 111,241 | 6.29 (4.82-7.77) | 1.05 (1.02-1.09) | 1.27 (1.00-1.62) |
| Second-generation | 58,036 (37.74) | 18 | 42,781 | 4.21 (2.26-6.15) | 0.78 (0.70-0.87) | 0.91 (0.57-1.45) |
| Third-generation | 27,110 (17.63) | 17 | 19,178 | 8.86 (4.65-13.08) | 0.99 (0.88-1.12) | 1.72 (1.05-2.80) |
| Fourth-generation | 68,651 (44.64) | 35 | 49,282 | 7.10 (4.75-9.45) | 1.07 (1.01-1.14) | 1.38 (0.97-1.96) |
aIRR, adjusted incidence rate ratio; IR, incidence rate; IRR, incidence rate ratio; N, number; Ref., reference; VT, venous thrombosis.
a
Adjusted for age and type of combined oral contraceptives in the Total group; adjusted for age only in the different generation groups.