Sample characteristics at baseline by zygosity, showing mean MRI trait scores for whole group and by age strata
| Age, years | Monozygotic twins | Dizygotic twins | p Value | |
|---|---|---|---|---|
| Sample size | 180 | 288 | ||
| Age, years, mean (range) | 55.42 (40.89–68.74) | 52.64 (40.08–68.75) | <0.01 | |
| Males, n (%) | 12 | 12 | 0.233 | |
| Body mass index, kg/m2 (range) | 24.39 (18.85–42.31) | 25.01 (17.51–45.14) | 0.10 | |
| Lumbar disc height score, mean (range) | All ages | 4.07 (0–13) | 3.80 (0–12) | 0.25 |
| <50 | 3.08 (1.59) | 3.48 (2.24) | 0.33 | |
| 50–60 | 3.95 (2.44) | 3.80 (3.36) | 0.64 | |
| >60 | 5.2142 (3.15) | 4.49 (2.71) | 0.23 | |
| Lumbar disc signal score, mean (range) | All ages | 6.21 (0–11) | 5.65 (0–12) | 0.03 |
| <50 | 4.19 (2.29) | 4.64 (2.69) | 0.37 | |
| 50–60 | 6.37 (2.44) | 5.80 (2.60) | 0.09 | |
| >60 | 7.57 (2.20) | 7.41 (2.15) | 0.73 | |
| Lumbar disc bulge score, mean (range) | All ages | 2.15 (0–8) | 1.97 (0–10) | 0.24 |
| <50 | 1.83 (1.42) | 1.87 (1.64) | 0.89 | |
| 50–60 | 2.12 (1.707) | 1.84 (1.54) | 0.20 | |
| >60 | 2.5 (1.81) | 2.47 (1.77) | 0.94 | |
| Lumbar anterior osteophyte score, mean (range) | All ages | 1.40 (0–7) | 0.99 (0–10) | <0.01 |
| <50 | 1.14 (1.59) | 0.77 (1.11) | 0.13 | |
| 50–60 | 1.24 (1.16) | 0.96 (1.22) | 0.08 | |
| >60 | 2.0 (1.82) | 1.53 (2.06) | 0.25 | |
| Summary lumbar score, mean (range) | All ages | 13.84 (0–38) | 12.41 (0–40) | 0.02 |
| <50 | 10.25 (4.93) | 10.77 (5.78) | 0.63 | |
| 50–60 | 13.68 (6.08) | 12.39 (6.05) | 0.12 | |
| >60 | 17.29 (6.55) | 15.91 (6.86) | 0.32 |
Summary lumbar score represente for all four traits over five lumbar disc levels. p Value is significance value comparing monozygotic with dizygotic twins.