Table 4.

Assessment of heterogeneity among studies examining the association between global DNA methylation and breast cancer risk

SubgroupEstimates (n)RR (95% CI); PI2Meta-regression P
Study demographics
 Mean age
  <5050.83 (0.58–1.19); P = 0.310.0%0.08
  50–<6050.47 (0.32–0.69); P = 0.0264.7%
  60+41.01 (0.54–1.90); P = 0.9792.0%
 Country
  North American100.83 (0.55–1.25); P = 0.3786.6%0.14
  Other40.47 (0.28–0.79); P = 0.00467.9%
Study design
 Type
  Prospectivea50.62 (0.43–0.87); P = 0.00758.1%0.49
  Case–control90.77 (0.45–1.32); P = 0.3490.1%
 Blood draw type
  >3 years prior to diagnosis30.52 (0.28–0.97); P = 0.0471.5%0.37
  <3 years prior to diagnosis110.77 (0.49–1.20); P = 0.2488.8%
DNA methylation assessment
 Genomic context
  Illumina 450k30.53 (0.27–1.06); P = 0.0769.8%0.26
  Global30.59 (0.33–1.04); P = 0.0769.9%
  Repetitive elements60.84 (0.63–1.13); P = 0.2554.0%
  LUMA41.02 (0.28–3.76); P = 0.9896.4%
 Assay type
  Non-LUMA120.64 (0.50–0.83); P < 0.00158.3%0.25
  LUMA31.02 (0.28–3.76); P = 0.9896.4%
  • aIncludes nested case–control studies.