Table 2 Subgroup analysis of the relationship between hypertension and risk of breast cancer.

From: Hypertension and breast cancer risk: a systematic review and meta-analysis

Characteristics No. of studies RR (95% CI) I2 (%) P-valuea P-valueb
Total 30 1.15 (1.08,1.22) 72.30 <0.001  
Geographical region
 America 14 1.18 (1.06,1.31) 72.80 <0.001 0.84
 Europe 11 1.16 (1.05,1.29) 78.90 <0.001  
 Asia 5 1.07 (0.94,1.22) 29.40 0.23  
Study design
 Retrospective 18 1.29 (1.14,1.47) 77.80 <0.001 0.22
 Prospective 12 1.07 (1.01,1.14) 57.30 0.01  
Number of breast cancer cases
 <200 9 1.20 (0.97,1.47) 62.90 0.01 0.98
 ≥200 20 1.15 (1.07,1.25) 75.40 <0.001  
Data extracted from Mets studies
 Yes 7 1.26 (1.08,1.47) 59.40 0.02 0.38
 No 23 1.12 (1.05,1.20) 74.50 <0.001  
Study quality
 NOS < 7 16 1.21 (1.10,1.34) 80.10 <0.001 0.88
 NOS ≥ 7 14 1.09 (1.01,1.17) 45.30 0.03  
Definition of hypertension
 ≥130/85mmhg 11 1.14 (1.02,1.26) 54.40 0.02
 ≥140/90mmhg 3 2.18 (1.31,3.65) 42.40 0.18  
 ≥160/95mmhg 3 1.09 (0.91,1.31) 79.70 0.01  
Menopausal status
 Premenopausal 9 0.97 (0.84,1.12) 29.30 0.19
 Postmenopausal 13 1.20 (1.09,1.31) 63.20 0.001  
  1. RR, relative risk; CI, confidence interval; NOS, Newcastle–Ottawa Quality Assessment Scale; P-valuea, p for heterogeneity within each subgroup; P-valueb., p for heterogeneity between subgroups.