. Author manuscript; available in PMC: 2019 Oct 1.

Published in final edited form as: Eur J Epidemiol. 2018 May 14;33(10):965–976. doi: 10.1007/s10654-018-0402-z

Table 2.

Meta-analysis derived Odds Ratios (OR) and 95% Confidence Intervals (95% CI) from the five registry-based case-control studies (Canada-Quebec; Denmark; Finland; US, California State, CCLRP; US, Washington State) on the association of the combined effect of maternal and paternal age at birth of the index child with childhood (0–14 years) acute lymphoblastic leukemia.

ALL cases/ controls, OR (95% CI)^a	Paternal age <25 years	Paternal age 25–34 years	Paternal age ≥35 years
Maternal age <25 years	1181/4318 0.84 (0.77–0.91) I²: 0%, p=0.53	1036/3357 0.96 (0.82–1.12) I²: 55%, p=0.07	87/279 1.17 (0.77–1.77) I²:45%, p=0.12
Maternal age 25–34 years	192/678 0.88 (0.74–1.04) I²: 0%, p=0.71	3382/10122 Reference	1114/3343 1.05 (0.97–1.13) I²: 0%, p=0.80
Maternal age ≥35 years	192/678 0.88 (0.74–1.04) I²: 0%, p=0.71	264/793 1.07 (0.92–1.24) I²: 0%, p=0.64	906/2582 1.16 (1.04–1.28) I²: 11%, p=0.34

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 with <20% missing values in the total dataset: 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).