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Table 4 Subgroup analysis of association between breastfeeding and risk of childhood brain tumors for the comparison of breastfeeding versus non/occasional breastfeeding

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

  No. of studies No. of cases OR (95%CI) P value I2 (%) P value for heterogeneity P in meta-regression
Cancer type        0.396
 Ependymoma (C.1) 4 408 1.02 (0.65 ~ 1.60) 0.931 22.3 0.277  
 Astrocytoma (C.2) 4 475 0.91 (0.71 ~ 1.15) 0.411 0.0 0.589  
 Medulloblastoma (C.3) 2 148 0.89 (0.42 ~ 1.92) 0.770 53.4 0.143  
 Others (C.4) 3 446 1.13 (0.83 ~ 1.55) 0.446 22.1 0.274  
Year of publication        0.665
 In and before 2005 (C.5) 4 640 0.95 (0.69 ~ 1.30) 0.751 37.8 0.186  
 After 2005 (C.6) 3 1019 0.94 (0.80 ~ 1.10) 0.431 0.0 0.458  
Geographic location        0.296
 North America (C.7) 2 310 0.74 (0.55 ~ 1.01) 0.055 0.0 0.364  
 Europe (C.8) 4 1071 1.03 (0.90 ~ 1.19) 0.639 0.0 0.636  
 Oceania (C.9) 1 278 0.81 (0.47 ~ 1.39) 0.443 NA NA  
Study quality score        0.847
 ≤ 7 (C.10) 5 926 0.92 (0.72 ~ 1.16) 0.472 35.6 0.184  
 > 7 (C.11) 2 733 0.98 (0.82 ~ 1.17) 0.825 0.0 0.479  
Sample size        0.179
 ≤ 1000 (C.12) 4 631 0.81 (0.62 ~ 1.06) 0.121 4.7 0.369  
 > 1000 (C.13) 3 1028 1.02 (0.89 ~ 1.17) 0.772 0.0 0.560  
Definition of reference category        0.665
 Never breastfeeding (C.14) 3 1019 0.94 (0.80 ~ 1.10) 0.431 0.0 0.458  
 Occasional breastfeeding (C.15) 4 640 0.95 (0.69 ~ 1.30) 0.751 37.8 0.186 0.207
  ≤ 2 months (C.16) 3 602 1.08 (0.88 ~ 1.32) 0.482 0.0 0.489  
  ≤ 6 months (C.17) 1 38 0.57 (0.30 ~ 1.09) 0.088 NA NA  
  1. Abbreviations: PC-CS population-based case-control study; HC-CS hospital-based case-control study; NA not applicable