Table 1.
Crude incidence rate and adjusted relative risk of confirmed venous thrombosis according to age, calendar year, and length of education
| Variables | Woman years | Venous thrombosis | Incidence per 10 000 woman years | Adjusted relative risk* (95% CI) | P value | |
|---|---|---|---|---|---|---|
| All | Confirmed | |||||
| Age: | ||||||
| 15-19 | 1 403 925 | 365 | 251 | 1.79 | 0.16 (0.13 to 0.19) | <0.001 |
| 20-24 | 1 198 098 | 479 | 326 | 2.72 | 0.19 (0.16 to 0.22) | <0.001 |
| 25-29 | 1 145 729 | 594 | 387 | 3.38 | 0.30 (0.27 to 0.33) | <0.001 |
| 30-34 | 1 299 645 | 715 | 448 | 3.45 | 0.44 (0.40 to 0.48) | <0.001 |
| 35-39 | 1 509 447 | 930 | 601 | 3.98 | 0.60 (0.55 to 0.66) | <0.001 |
| 40-44 | 1 510 042 | 1105 | 705 | 4.67 | 0.82 (0.75 to 0.89) | <0.001 |
| 45-49 | 1 362 242 | 1099 | 716 | 5.26 | 1.00 (reference) | — |
| Year: | ||||||
| 2001 | 994 095 | 444 | 315 | 3.17 | 0.70 (0.61 to 0.79) | <0.001 |
| 2002 | 979 715 | 466 | 331 | 3.38 | 0.72 (0.64 to 0.82) | <0.001 |
| 2003 | 963 470 | 438 | 304 | 3.16 | 0.68 (0.60 to 0.77) | <0.001 |
| 2004 | 953 604 | 512 | 319 | 3.35 | 0.79 (0.70 to 0.89) | <0.001 |
| 2005 | 939 935 | 525 | 362 | 3.85 | 0.81 (0.72 to 0.91) | 0.0005 |
| 2006 | 929 975 | 537 | 363 | 3.90 | 0.84 (0.74 to 0.94) | 0.0028 |
| 2007 | 921 713 | 615 | 391 | 4.24 | 0.97 (0.87 to 1.09) | 0.6531 |
| 2008 | 918 349 | 538 | 347 | 3.78 | 0.87 (0.77 to 0.98) | 0.0171 |
| 2009 | 911 825 | 599 | 365 | 4.00 | 0.98 (0.87 to 1.09) | 0.6597 |
| 2010 | 916 449 | 613 | 337 | 3.68 | 1.00 (reference) | — |
| Education: | ||||||
| 1 (low) | 2 164 635 | 1819 | 1159 | 5.35 | 1.25 (1.11 to 1.42) | 0.0004 |
| 2 | 1 026 525 | 475 | 314 | 3.06 | 0.72 (0.62 to 0.83) | <0.001 |
| 3 | 2 236 972 | 1456 | 974 | 4.35 | 0.83 (0.73 to 0.95) | 0.0087 |
| 4 (high) | 1 385 214 | 602 | 382 | 2.76 | 0.61 (0.53 to 0.71) | <0.001 |
| Not available | 2 615 782 | 935 | 605 | 2.31 | 1.00 (reference) | — |
*Adjusted for age, calendar year, education, and use of hormonal contraception.