Characteristics of the UK Twins Spine study sample by LBP status
| LBP1 absent | LBP1 present | ||||||
|---|---|---|---|---|---|---|---|
| Predictor variable | X | SD | N | X | SD | N | ANOVA (F), p value |
| Age (year) | 49.95 | 11.78 | 1710 | 51.48 | 10.28 | 546 | 7.34, 0.007* |
| Height (m) | 1.62 | 0.06 | 1710 | 1.63 | 0.06 | 546 | 12.00, 0.0004* |
| Weight (kg) | 64.89 | 11.32 | 1709 | 68.97 | 12.93 | 544 | 49.97, 0.0001* |
| BMI (kg/m2) | 24.69 | 4.29 | 1709 | 25.92 | 4.79 | 544 | 33.21, 0.0001* |
| Smoking (packs/year) | 4.10 | 9.68 | 1050 | 4.19 | 10.27 | 302 | 0.7, 0.413† |
| (672.70)† | (689.72)† | ||||||
| Manual work | 2.19 | 6.46 | 1710 | 2.97 | 6.92 | 546 | 5.80, 0.016† |
| (1120.03)† | (1208.80)† | ||||||
| PhysExers‡ (yes) | 60.73% | 753 | 80.76% | 361 | χ2=58.8, <0.0001 | ||
| LHT | 3.45 | 2.56 | 654 | 4.93 | 2.83 | 182 | 45.40, 0.001* |
| LSIG | 5.70 | 3.28 | 656 | 7.07 | 2.99 | 183 | 25.96, 0.001* |
| LBUL | 2.00 | 1.74 | 656 | 2.86 | 1.84 | 183 | 33.87, 0.001* |
| LOST | 1.35 | 1.85 | 654 | 1.99 | 2.42 | 183 | 14.98, 0.001* |
| LSUM | 12.52 | 7.30 | 652 | 16.82 | 7.92 | 182 | 47.67, 0.001* |
| LBP1_Q¶ | 0.714 | 1.887 | 1730 | 5.083 | 2.622 | 522 | 1256.02, 0.0001† |
| (902.75)† | (1889.75)† | ||||||
LBP_1 represents low back pain (LBP) defined as pain associated with disability lasting more than a month over life time (other LBP phenotypes defined in the Patients and methods section).
* The analysis of variance (ANOVA) result was confirmed by Kruskal–Wallis test.
† Kruskal–Wallis test (χ2 and p value), mean group ranks are provided in parentheses.
‡ Percentage who exercised.
§ Percentage who complained.
¶ LBP1-absent individuals can have LBP1_Q>0, if the length of time they have had back pain is less than 1 month throughout their whole life. For an individual to be LBP1-present, they need to have disabling pain lasting longer than 1 month.
BMI, body mass index; LBUL, disc bulge; LHT, disc height; LOST, anterior osteophytes; LSIG, disc signal intensity; LSUM, summary rank for four lumbar disc degeneration traits; N, sample size; X, mean or proportion.