Table 1. Characteristics of the Study Population.
| Characteristic | No. (%) | ||
|---|---|---|---|
| Warfarin Users | Nonusers | Total | |
| Sex | |||
| Male | 57 370 (61.7) | 549 980 (47.3) | 607 350 (48.3) |
| Female | 35 572 (38.3) | 613 803 (52.7) | 649 375 (51.7) |
| Total | 92 942 (7.4) | 1 163 783 (92.6) | 1 256 725 |
| Person-years | 430 266 (5.4) | 7 577 952 (94.6) | 8 008 218 |
| Follow-up time, mean (SD), y | 4.6 (2.2) | 6.3 (1.7) | 6.2 (1.8) |
| Year of birth | |||
| 1924-1933 | 42 830 (46.1) | 226 079 (19.4) | 268 909 (21.4) |
| 1934-1943 | 30 166 (32.4) | 323 003 (27.8) | 353 169 (28.1) |
| 1944-1954 | 19 942 (21.5) | 614 701 (52.8) | 634 647 (50.5) |
| Age, mean (SD), y | 70.2 (8.2) | 63.9 (8.6) | |
| Deaths in study period | 20 502 (22.1) | 124 480 (10.7) | 144 982 (11.5) |
| Cancer diagnosis | 8754 (9.4) | 123 933 (10.6) | 132 687 (10.6) |
| Duration of warfarin use, mo | |||
| 6 to 11 | 9520 (10.2) | NA | |
| 12-24 | 11 734 (12.7) | NA | |
| >24 | 71 688 (77.1) | NA | |
| Duration of use, mean (SD), y | 4.8 (2.8) | NA | |
| Duration of use, median (IQR), y | 4.7 (2.2-7.8) | NA | |
| Reason for warfarin usea | |||
| Atrial fibrillation or atrial flutter (ICD-10-CM I48; ICPC K78) | 33 313 (35.8) | NA | |
| Pulmonary embolism (ICD-10-CM I26; ICPC K93) | 3141 (3.4) | NA | |
| Phlebitis (ICD-10-CM I80, I82; ICPC K94) | 2173 (2.3) | NA | |
| Ischemic heart disease (ICD-10-CM -22, I20-I22, I25; ICPC -22, -26, -27, K74-K76) | 9055 (9.7) | NA | |
| Cerebral ischemia (ICD-10-CM G45, I63; ICPC K89, K90) | 2121 (2.3) | NA | |
| Valvular defect (ICD-10-CM I34, I35, Z94, Z95; ICPC -51, A89, K83) | 1425 (1.5) | NA | |
| Other | 41 714 (44.8) | NA | |
Abbreviations: ICD-10-CM, International Classification of Diseases, Tenth Edition, Clinical Modification; ICPC, International Classification of Primary Care, Second Edition; IQR, interquartile range; NA, not applicable.
a
The following designations represent reimbursement codes used by the Norwegian Medicines Agency in addition to ICD-10 and ICPC: -22 indicates secondary prophylaxis after heart attack; -26, atherosclerotic disease (secondary prophylaxis); -27, increased risk of developing atherosclerotic disease (primary prophylaxis); and -51, organ transplant (transplanted heart valve).