Table 2.
Pairwise distribution of Low back pain (LBP) frequency by sex and zygosity
| LBP twin 1 | LBP in twin 2, N (% of total FMZ twins) | |||
|---|---|---|---|---|
| No. | Monthly | Weekly | Total | |
| Monozygotic females (FMZ) | ||||
| No | 206 (69.4) | 20 (6.7) | 8 (2.7) | 234 |
| Monthly | 22 (7.4) | 16 (5.4) | 2 (0.7) | 40 |
| Weekly | 10 (3.7) | 7 (2.4) | 6 (2.0) | 23 |
| Total | 238 | 43 | 16 | 297 |
| Polychoric correlation = 0.58 (95% CI 0.43–0.73) | ||||
| LBP in twin 2, N (% of total MMZ twins) | ||||
| Monozygotic males (MMZ) | ||||
| No | 188 (60.1) | 29 (9.3) | 18 (5.8) | 235 |
| Monthly | 28 (9.0) | 19 (6.1) | 5 (1.6) | 52 |
| Weekly | 12 (3.8) | 7 (2.2) | 7 (2.2) | 26 |
| Total | 228 | 55 | 30 | 313 |
| Polychoric correlation = 0.41 (95% CI 0.25–0.57) | ||||
| LBP in twin 2, N (% of total FDZ twins) | ||||
| Dizygotic females (FDZ) | ||||
| No | 189 (9.7) | 28 (10.3) | 5 (1.8) | 222 |
| Monthly | 20 (7.4) | 10 (3.7) | 3 (1.1) | 33 |
| Weekly | 11 (4.1) | 1 (0.4) | 4 (1.5) | 16 |
| Total | 220 | 39 | 12 | 271 |
| Polychoric correlation = 0.40 (95% CI 0.19–0.61) | ||||
| LBP in twin 2, N (% of total MDZ twins) | ||||
| Dizygotic males (MDZ) | ||||
| No | 194 (59.3) | 37 (11.3) | 11 (3.4) | 242 |
| Monthly | 35 (10.7) | 16 (4.9) | 9 (2.8) | 60 |
| Weekly | 13 (4.0) | 4 (1.2) | 8 (2.4) | 25 |
| Total | 242 | 57 | 28 | 327 |
| Polychoric correlation = 0.40 (95% CI 0.24–0.56) | ||||
| LBP in female twins, N (% of total OSDZ twins) | ||||
| Dizygotic Opposite sex (OSDZ) | ||||
| No | 375 (64.4) | 65 (11.2) | 18 (3.1) | 458 |
| Monthly | 68 (11.7) | 18 (3.1) | 6 (1.0) | 92 |
| Weekly | 15 (2.6) | 9 (1.5) | 8 (1.4) | 32 |
| Total | 458 | 92 | 32 | 582 |
| Polychoric correlation = 0.32 (95% CI 0.18–0.46) | ||||