Table 2.
Risk factors for childhood leukemia.
| Characteristics | Patients | Controls | OR | 95% CI | p-Value |
|---|---|---|---|---|---|
| The family history of cancer | |||||
| No | 867 (90.5) | 767 (97.7) | 0.926 | 0.905–0.948 | <0.0001 |
| Yes | 91 (9.5) | 18 (2.3) | 4.413 | 2.521–6.808 | <0.0001 |
| The family history of neoplasm of the lymphatic/hematopoietic systems | |||||
| No | 930 (97.1) | 782 (99.6) | 0.947 | 0.963–0.986 | <0.0001 |
| Yes | 28 (2.9) | 3 (0.4) | 0.947 | 2.334–25.062 | <0.0001 |
| History of bedroom decoration | |||||
| No | 567 (59.2) | 490 (62.4) | 0.948 | 0.879–1.023 | 0.169 |
| Yes | 391 (40.8) | 295 (37.6) | 1.086 | 0.965–1.222 | 0.169 |
| Smoking during pregnancy | |||||
| No | 945 (98.6) | 782 (99.6) | 0.990 | 0.982–0.999 | 0.034 |
| Yes | 13 (1.4) | 3 (0.4) | 3.551 | 1.051–12.416 | 0.034 |
| The history of using birth control pills before pregnancy | |||||
| No | 912 (95.2) | 764 (97.3) | 0.978 | 0.960–0.996 | 0.022 |
| Yes | 46 (4.8) | 21 (2.7) | 1.795 | 1.081–2.982 | 0.022 |
| Abortion history | |||||
| No | 703 (73.4) | 629 (80.1) | 0.916 | 0.870–0.964 | 0.001 |
| Yes | 255 (26.6) | 156 (19.9) | 1.339 | 1.124–1.569 | 0.001 |
| Down’s syndrome | |||||
| No | 937 (97.8) | 785 (99.7) | 0.981 | 0.971–0.991 | <0.0001 |
| Yes | 21 (2.2) | 2 (0.3) | 8.640 | 2.024–36.581 | <0.0001 |
| Parents use of hair dye | |||||
| No | 826 (86.2) | 728 (92.7) | 0.252 | 0.54–1.171 | 0.079 |
| 3 months before pregnancy | 62 (6.5) | 54 (6.9) | 0.255 | 0.53–1.233 | 0.089 |
| During pregnancy | 9 (0.9) | 2 (0.3) | 1 | ||
| During breastfeeding | 61 (6.4) | 1 (0.1) | 13.556 | 1.112–125.206 | 0.041 |
| Breastfeeding | |||||
| Ever breastfed | 695 (72.5) | 756 (96.3) | 0.753 | 0.723–0.785 | <0.0001 |
| Never breastfed | 263 (27.5) | 29 (3.7) | 7.431 | 5.124–10.777 | <0.0001 |
| Breastfeeding period | |||||
| 0 month | 263 (27.5) | 29 (3.7) | 8.023 | 4.620–13.930 | <0.0001 |
| 1–3 months | 102 (10.6) | 87 (11.1) | 1.037 | 0.636–1.691 | 0.884 |
| 4–6 months | 158 (16.5) | 186 (23.7) | 0.751 | 0.479–1.178 | 0.213 |
| 7–9 months | 135 (14.1) | 240 (30.6) | 0.498 | 0.318–0.780 | 0.002 |
| 10–12 months | 248 (25.9) | 197 (25.1) | 1.114 | 0.718–1.727 | 0.631 |
| More than 13 months | 52 (5.4) | 46 (5.9) | 1 | ||
| Breastfeeding pattern | |||||
| Exclusive breastfeeding | 489 (51) | 529 (67.4) | 1.019 | 0.813–1.276 | 0.872 |
| Nonexclusive breast milk feeding | 206 (21.5) | 227 (28.9) | 1 | ||
| Pure milk powder | 263 (27.5) | 29 (3.7) | 9.993 | 6.518–15.322 | <0.0001 |
For multivariate analysis, non-conditional logistic regression analysis was applied. p < 0.05 compared with control group. Odds ratios (ORs) and 95% confidence intervals (CIs) are presented.