Table 3 Summary relative risks and 95%CI for the association between endometriosis and breast cancer by study characteristics
Subgroup | No.of studies | Pooled RR(95%CI) | Heterogeneity | ||
|---|---|---|---|---|---|
Random effect | Fixed effect | P | I2(%) | ||
| Â | 16 | 1.082 (1.001,1.169) | 1.048 (1.022,1.074) | 0.000 | 82.7 |
The way of information collection | |||||
 questionnaire | 3 | 0.711 (0.450,1.124) | 0.933 (0.852,1.022) | 0.027 | 72.3 |
 database | 11 | 1.134 (1.037,1.241) | 1.058 (1.030,1.086) | 0.000 | 86.1 |
 both questionnaire and database | 1 | 1.120 (0.930,1.349) | 1.120 (0.930,1.350) | – | – |
 telephone interview | 1 | 0.990 (0.805,1.218) | 0.990 (0.805,1.219) | – | – |
Study design | |||||
 Case-control studies | 4 | 0.877 (1.001,1.169) | 1.071 (0.929,1.234) | 0.000 | 83.3 |
 Cohort studies | 12 | 1.094 (1.011,1.183) | 1.047 (1.021,1.074) | 0.000 | 83.9 |
Endometriosis assessment | |||||
 Self-report | 4 | 0.859 (0.642,1.149) | 0.989 (0.868,1.128) | 0.018 | 70.3 |
 surgery | 3 | 1.030 (0.925,1.148) | 0.996 (0.957,1.037) | 0.022 | 73.7 |
 ICD | 7 | 1.206 (1.000,1.455) | 1.127 (1.079,1.178) | 0.000 | 88.1 |
 Other | 2 | 1.040 (0.991,1.092) | 1.040 (0.991,1.092) | 0.341 | 0.0 |
Ascertainment of breast cancer | |||||
 Histopathology reports | 2 | 0.547 (0.365,0.821) | 0.547 (0.365,0.821) | 0.632 | 0.0 |
 ICD | 11 | 1.134 (1.037,1.241) | 1.058 (1.030,1.086) | 0.000 | 86.1 |
 Other | 3 | 0.992 (0.915,1.076) | 0.990 (0.916,1.069) | 0.349 | 5.0 |
NOS score | |||||
 <7 | 9 | 1.051 (0.991,1.114) | 1.026 (0.999,1.055) | 0.006 | 63.0 |
  ≥ 7 | 7 | 1.052 (0.836,1.327) | 1.159 (1.091,1.230) | 0.000 | 88.4 |
Adjustment for age | |||||
 Yes | 11 | 1.060 (0.924,1.217) | 1.083 (1.042,1.125) | 0.000 | 85.4 |
 No | 5 | 1.055 (0.977,1.138) | 1.024 (0.991,1.058) | 0.010 | 69.7 |
Adjustment for BMI | |||||
 Yes | 4 | 0.860 (0.696,1.164) | 0.942 (0.867,1.024) | 0.058 | 59.9 |
 No | 12 | 1.133 (1.041,1.233) | 1.059 (1.032,1.087) | 0.000 | 84.8 |
Adjustment for oral contraceptive use history | |||||
 Yes | 3 | 0.968 (0.890,1.053) | 1.968 (0.890,1.053) | 0.834 | 0.000 |
 No | 13 | 1.101 (1.008,1.203) | 1.056 (1.029,1.084) | 0.000 | 85.5 |
Adjustment for pregnancies | |||||
 Yes | 3 | 1.004 (0.959,1.051) | 1.004 (0.959,1.052) | 0.539 | 0.000 |
 No | 13 | 1.108 (0.998,1.231) | 1.067 (1.036,1.099) | 0.000 | 85.1 |
Adjustment for smoking | |||||
 Yes | 3 | 0.711 (0.450,1.124) | 0.933 (0.852,1.022) | 0.027 | 72.3 |
 No | 13 | 1.122 (1.035,1.216) | 1.058 (1.031,1.085) | 0.000 | 83.5 |
Adjustment for family history of breast cancer | |||||
 Yes | 4 | 0.860 (0.696,1.064) | 0.942 (0.867,1.024) | 0.058 | 59.9 |
 No | 12 | 1.133 (1.041,1.233) | 1.059 (1.032,1.087) | 0.000 | 84.8 |