Table 1.
Baseline Characteristics Presented as Mean (SD) or Proportions.
| Characteristic | Total | Denmark | Norway | Sweden | P |
|---|---|---|---|---|---|
| Number of patients, n | 1839 | 392 | 300 | 1147 | |
| Age, years, mean (SD) | 45.3 (9.9) | 48.1 (10.7) | 43.9 (10.3) | 44.7 (9.3) | <.001a |
| BMI, kg/m2, mean (SD) | 26.2 (3.9) | 26.6 (4.2) | 26.4 (4.3) | 26.0 (3.7) | <.02a |
| Females, n (%) | 1039 (56) | 238 (61) | 165 (55) | 636 (55) | .16b |
| Smokers, n (%) | 282 (15) | 107 (27) | 81 (27) | 94 (8) | <.001b |
| Preoperative pain medication, n (%) | 1635 (90) | 326 (84) | 270 (93) | 1039 (91) | <.001b |
| Neurological comorbidity, n (%) | 20 (1) | 3 (1) | 4 (1) | 13 (1%) | .75b |
| Heart comorbidity, n (%) | 26 (1.4) | 14 (3.6) | 2 (0.7) | 10 (0.9) | <.001b |
| Cancer comorbidity, n (%) | 9 (0.5) | 6 (1.5) | 1 (0.3) | 2 (0.2) | .004b |
| Preoperative duration of leg pain >12 months, n (%) | 1136 (63) | 253 (68) | 176 (61) | 707 (62) | .12b |
| Preoperative duration of back pain >12 months, n (%) | 1613 (88) | 331 (85) | 256 (88) | 1026 (90) | .04b |
| ODI, mean (SD) | 43 (14.2) | 44 (14.7) | 42 (14.0) | 44 (14.1) | .26a |
| NRS leg pain, mean (SD) | 4.3 (3.0) | 5.7 (2.8) | 4.2 (3.2) | 3.9 (2.9) | <.001a |
| NRS back pain, mean (SD) | 6.3 (2.2) | 6.9 (1.8) | 5.3 (2.9) | 6.4 (2.0) | <.001a |
| EQ-5D-3L, mean (SD) | 0.32 (0.32) | 0.29 (0.33) | 0.36 (0.30) | 0.32 (0.33) | .02a |
| Responding at the 1-year follow-up, n (%) | 1315 (72) | 259 (66) | 164 (55) | 892 (78) | <.001b |
Abbreviations: SD, standard deviation; BMI, body mass index; ODI, Oswestry Disability Index; NRS, numeric rating scale.
aAnalysis of variance F test.
bPearson’s chi-square test.