Characteristics of the OA population from the BOA Register and the reference cohort and differences in comorbidities between the populations identified by the comorbidity indices
| OA population (n=72 069) | Reference cohort (n=216 207) | |
| Age (years) mean (SD) | 66.4 (9.6) | 66.4 (9.6) |
| Women, % (n) | 69 (49 494) | 69 (148 482) |
| Most affect joint in the OA population, % (n) | ||
| Hip | 32 (22 703) | |
| Knee | 68 (49 366) | |
| OA in multiple joints,* % (n) | 62 (44 384) | |
| Missing | n=443 | |
| Born outside Sweden, % (n) | 9 (6474) | 13 (28 554) |
| Missing | n=0 | n=12 |
| Married, % (n) | 59 (42 359) | 54 (117 616) |
| Missing | n=9 | n=162 |
| Educational level, % (n) | ||
| Low (≤9 years) | 22.5 (16 276) | 28.5 (61 212) |
| Medium (10–14 years) | 60.5 (43 492) | 56 (119 416) |
| High (≥15 years) | 17 (12 111) | 15.5 (33 260) |
| Missing | n=190 | n=2319 |
| Comorbidities indices | ||
| Missing | n=0 | n=0 |
| RxRisk Index† median (IQR); min-max scores | 3 (4); 0–18 | 2 (4); 0–18 |
| 0 (no comorbidities), % (95% CI) | 16 (15.7 to 16.3) | 23 (22.8 to 23.2) |
| 1–3 | 44 (43.6 to 44.4) | 40.5 (40.3 to 40.7) |
| ≥4 | 40 (39.6 to 40.4) | 36.5 (36.3 to 36.7) |
| Elixhauser Comorbidity Index, median (IQR); min-max scores | 0 (1); 0–11 | 0 (1); 0–13 |
| 0 (no comorbidities), % (95% CI) | 69.5 (69.2 to 69.8) | 69 (68.8 to 69.2) |
| 1 | 16.5 (16.2 to 16.8) | 16 (15.8 to 16.2) |
| ≥2 | 14 (13.7 to 14.3) | 15 (14.8 to 15.2) |
| Charlson Comorbidity Index, median (IQR); min-max scores | 0 (0); 0-11 | 0 (0); 0-15 |
| 0 (no comorbidities), % (95% CI) | 81 (80.7 to 81.3) | 78 (77.8 to 78.2) |
| 1 | 9.5 (9.3 to 9.7) | 10 (9.9 to 10.1) |
| ≥2 | 9.5 (9.3 to 9.7) | 12 (11.9 to 12.1) |
| Comorbidities (≥1) grouped by age, % (95% CI)† | ||
| <45 years (OA n=1583; ref n=4749) | 65 (62.7 to 67.3) | 51 (49.6 to 52.4) |
| 46–65 years (OA n=29 225; ref n=87 675) | 79 (78.5 to 79.5) | 69 (68.7 to 69.3) |
| 66–80 years (OA n=36 993; ref n=110 979) | 90 (89.7 to 90.3) | 84.5 (84.3 to 84.7) |
| >81 years (OA n=4268; ref n=12 804) | 96 (95.4 to 96.6) | 94 (93.6 to 94.4) |
*Osteoarthritis in multiple joints, identified as B or C Charley Class, a self-reported classification of musculoskeletal impairment. Class A indicates unilateral hip or knee OA, class B; bilateral hip or knee OA and class C; multiple joint OA or some other condition affecting the patient’s ability to walk.
†The conditions ‘inflammation/pain’ and ‘pain’ are excluded from the score count.
BOA, Better Management of Patients with Osteoarthritis; n, numbers; OA, osteoarthritis.