Figure 8

Meta-analysis for the association between twinship and risk for breast cancer. The tests for homogeneity and for publication bias in the studies analyzed are as follows. Twinship: Q = 18.79 (13 degrees of freedom), P = 0.13; Begg test, P = 0.78; Egger test, P = 0.24. Monozygote twin: Q = 5.79 (6 degrees of freedom), P = 0.45; Begg test, P = 0.55; Egger test, P = 0.85. Dizygote twin: Q = 12.53 (6 degrees of freedom), P = 0.06; Begg test, P = 1.0; Egger test, P = 0.3. ¹The authors used the female twins as the proxy for the monozygote twin and the female twin with male twin as the proxy for the dizygote twin. ²Women aged 21 to 45 years. ³Women aged 50 to 64 years. CI, confidence interval; OR, odds ratio.