Breastfeeding and the risk of childhood cancer: a systematic review and dose-response meta-analysis

Table 3 Subgroup analysis of association between breastfeeding and childhood lymphoma risk for the comparison of breastfeeding versus non/occasional breastfeeding

	No. of studies	No. of cases	OR (95%CI)	P value	I² (%)	P value for heterogeneity	P in meta- regression
Cancer type							0.875
Hodgkin’s disease (B.1)	9	458	0.86 (0.63 ~ 1.18)	0.341	25.8	0.215
Non-Hodgkin’s lymphoma (B.2)	9	686	0.88 (0.67 ~ 1.15)	0.343	26.9	0.205
Year of publication							0.583
In and before 2000 (B.3)	4	244	0.75 (0.53 ~ 1.06)	0.103	0.0	0.908
After 2000 (B.4)	7	980	0.84 (0.63 ~ 1.12)	0.231	51.5	0.054
Geographic location							0.041
Europe (B.5)	6	939	0.98 (0.84 ~ 1.15)	0.826	0.0	0.571
Asia (B.6)	4	259	0.53 (0.37 ~ 0.76)	0.001	0.0	0.906
North America (B.7)	1	26	0.69 (0.30 ~ 1.58)	0.381	NA	NA
Study quality score							0.436
< 7 (B.8)	2	85	0.66 (0.31 ~ 1.42)	0.290	39.7	0.198
≥ 7 (B.9)	9	1139	0.86 (0.70 ~ 1.06)	0.152	28.0	0.196
Sample size							0.578
≤ 200 (B.10)	5	368	0.77 (0.44 ~ 1.35)	0.366	45.5	0.119
> 200 (B.11)	6	856	0.89 (0.75 ~ 1.06)	0.203	12.7	0.334
Study design							0.743
PC-CS (B.12)	8	1068	0.85 (0.68 ~ 1.05)	0.125	34.1	0.156
HC-CS (B.13)	3	156	0.78 (0.41 ~ 1.51)	0.461	31.4	0.233
Definition of reference category							0.044
Never breastfeeding (B.14)	6	831	0.97 (0.83 ~ 1.14)	0.732	0.0	0.879
Occasional breastfeeding (B.15)	5	393	0.66 (0.44 ~ 0.99)	0.042	40.8	0.149	0.170
≤ 2 months (B.16)	2	216	1.07 (0.42 ~ 2.72)	0.888	68.3	0.076
≤ 6 months (B.17)	3	177	0.50 (0.34 ~ 0.75)	0.001	0.0	0.937

Abbreviations: PC-CS population-based case-control study; HC-CS hospital-based case-control study; NA not applicable

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