3.2 Ischemic heart disease
3.2.1 Pooled RR The pooled RR (95% CI) of ischemic heart disease risk for hysterectomy versus no hysterectomy was 1.20 (95% CI : 1.08-1.35; I2 =73.0%;Pheterogeneity = 0.000; Figure 2).
3.2.2 Subgroup analysis and meta-regression In subgroup analysis stratified by study design, the pooled RR was 1.15 (95% CI : 1.03-1.29; I2 =77.3%;Pheterogeneity = 0.000) in cohort studies; 1.27 (95% CI : 0.70-2.28; I2 =78.8%;Pheterogeneity = 0.001) in case-control studies; 1.61 (95% CI : 1.09-2.38; I2 =0%;Pheterogeneity = 0.487) in cross-sectional studies, respectively. In subgroup analysis stratified by continent, the pooled RR was 1.22 (95% CI : 0.90-1.66;I2 =60.1%;Pheterogeneity = 0.028) in North America; 1.20 (95% CI : 1.02-1.41; I2 =80.9%;Pheterogeneity = 0.000) in Europe and 1.20 (95% CI : 1.01-1.42; I2 =41.5%;Pheterogeneity = 0.181) in Asian. We also conducted the subgroup analysis stratified by publication year, more details were shown in Table S2. Meta-regressions of publication year (P =0.353), continent (P =0.801), study design (P =0.797), sample size (P =0.446), case number (P =0.992) were conducted to explore the between-study heterogeneity.
3.2.3 Sensitivity analysis In sensitivity analysis, after excluding 2 studies of 2 articles14, 39, the pooledRR was 1.21 (95% CI : 1.12-1.31) and theI2 dropped from 73.0% to 36.9%.
3.2.4 Influence analysis and publication bias Influence analysis showed that 1 study14 had an excessive influence on the pooledRR (Figure S1). After excluding the excessive influential study, the pooled result did not change obviously (RR : 1.24; 95% CI : 1.12-1.37; I2 = 53.8%;Pheterogeneity = 0.006). No significant small-study effect was found by visual inspection of the funnel plot (Figure S2) and Egger test (P =0.394).
3.2.5 Ovarian status, age at operation In the analysis between hysterectomy with ovarian preservation and risk of ischemic heart disease, the pooled RR was 1.33 (95% CI : 1.05-1.68;I2 =54.4%;Pheterogeneity = 0.012). The pooled RR was 1.31 (95% CI : 1.02-1.67; I2 =0%;Pheterogeneity = 0.446) in the relationship between hysterectomy with oophorectomy and risk of ischemic heart disease. The pooled RR was 1.19 (95% CI : 1.01-1.41;I2 =47.0%;Pheterogeneity = 0.067) in the association between having surgery before 50 years old and risk of ischemic heart disease; 1.16 (95% CI : 0.87-1.54;I2 =73.6%;Pheterogeneity = 0.002) for the association between having surgery after 50 years old and risk of ischemic heart disease. More details were shown in Table 1.