Table 3.
Meta-analysisa derived Odds Ratios (OR) and 95% Confidence Intervals (95% CI) on the association of parental age at birth of the index child with childhood (0–14 years) acute lymphoblastic leukemia in sub-analyses by index child’s age group, sex, ethnicity, and time period of diagnosis/recruitment, as determined by the 5 registry-based case-control studies (Canada-Quebec; Denmark; Finland; US, California State, CCLRP; US, Washington State).
| Variable | N ALL cases | N Controls | Paternal age (5-year increment) | Maternal age (5-year increment) | ||
|---|---|---|---|---|---|---|
| OR (95% CI) b | Heterogeneity I2, p | OR (95% CI) b | Heterogeneity I2, p | |||
| Index child’s age group (years) | ||||||
| <1 | 272 | 860 | 1.09 (0.92–1.29) | 0%, 0.53 | 0.98 (0.81–1.18) | 0%, 0.53 |
| 1–5 | 5270 | 16302 | 1.05 (1.01–1.09) | 0%, 0.83 | 1.04 (1.00–1.09) | 0%, 0.89 |
| 6–14 | 2621 | 8304 | 1.03 (0.90–1.19) | 74%, 0.004 | 1.06 (0.97–1.16) | 30%, 0.22 |
| Index child’s sex | ||||||
| Males | 4576 | 14293 | 1.07 (1.03–1.11) | 0%, 0.64 | 1.04 (1.00–1.09) | 0%, 0.54 |
| Females | 3586 | 11180 | 1.00 (0.96–1.05) | 0%, 0.96 | 1.05 (1.00–1.11) | 0%, 0.83 |
| Index child’s ethnicity | ||||||
| Caucasian | 4771 | 13898 | 1.06 (1.01–1.08) | 0%, 0.82 | 1.04 (0.99–1.08) | 0%, 0.67 |
| Non-Caucasian | 3348 | 11522 | 1.02 (0.97–1.06) | 0%, 0.38 | 1.06 (1.01–1.11) | 0%, 0.36 |
| Time period of diagnosis/recruitment | ||||||
| 1968–1993 | 2152 | 6076 | 1.01 (0.75–1.08) | 0%, 0.95 | 1.01 (0.89–1.15) | 56%, 0.06 |
| 1994–2003 | 3446 | 10939 | 1.04 (0.99–1.09) | 0%, 0.97 | 1.07 (1.00–1.15) | 20%, 0.29 |
| 2004–2015 | 2564 | 8458 | 1.06 (1.00–1.11) | 0%, 0.40 | 1.03 (0.98–1.10) | 0%, 0.50 |
Bold indicates statistical significance (p<0.05 for effect size and p<0.10 for heterogeneity). Maternal and paternal age are simultaneously introduced in all models.
Random-effect meta-analysis of maximally adjusted Odds Ratios from individual studies for any of the following variables that were available, apart if stratified for the specific variable: index child’s age (categorical; <1, 1–4 [reference], 5–9, 10–14 years), sex, ethnicity (Caucasian vs. non-Caucasian), birth weight (continuous; 500 gr increment), maternal education (categorical; low, intermediate [reference], high) pre-term birth (yes vs. no), maternal smoking during pregnancy (yes vs. no), multiple pregnancy (yes vs. no) and birth order (continuous; 1, 2, ≥3).