4.5 Limitations
Some limitations should be considered. Firstly, time of oophorectomy relative to hysterectomy is an important factor on CVD risk.10, 14 However, because of the insufficiency of data, we did not assess the association between the different time of oophorectomy relative to hysterectomy (having oophorectomy before hysterectomy, having hysterectomy and oophorectomy at the same time and having oophorectomy after hysterectomy) and the risk of CVD. Secondly, whether hysterectomy with oophorectomy is worse in risk of CVD than hysterectomy with ovarian preservation or not is still controversial.26, 48 In our meta-analysis, we found a 33% increase of ischemic heart disease risk in hysterectomy with ovarian preservation and a 31% increase in hysterectomy with oophorectomy. A statistical test is needed to assess whether there is a difference between hysterectomy only and hysterectomy with oophorectomy. But due to the deficiency of the data, we cannot compare the statistical difference between the two situations. Thirdly, moderate to high between-study heterogeneity was found, but it was not completely explained by subgroup analyses and meta-regressions. Presumably, confounders were different in each study, that may be an important determinant in the heterogeneity. And the underlying confounders may have contributed to the heterogeneity.
5 Conclusion In summary, hysterectomy, whether the ovarian preservation or not, might increase the risk of ischemic heart disease and hypertension, not of stroke. Hysterectomy might increase the risk of ischemic heart disease and stroke in women who had surgery before 50y; in women who had surgery after 50y, the results were nonsignificant.