3.1 Literature search and study characteristics
A total of 6706 articles were identified by search strategy. Seven additional articles were found in reference lists of retrieved studies. After removing the duplications and uncorrelated articles which were checked by screening titles and abstracts, 264 articles were included. We excluded 250 articles because: reviews (n=11); full texts were not available (n=30); the association of interest was not evaluated (n=71);OR , RR or HR and corresponding 95% CI were not available (n=138). Ultimately, 14 articles10-16, 24-27, 31, 38, 39 which fulfilled the inclusion criteria were included in the meta-analysis (Figure 1).
Of the 17 studies about ischemic heart disease, there are 9 cohort studies, 3 cross-sectional studies, and 5 case-control studies. Twelve studies investigated the relationship between hysterectomy with ovarian preservation and ischemic heart disease, 4 studies researched the relationship between hysterectomy with oophorectomy and ischemic heart disease. The relationships between surgery before 50 years old or surgery after 50 years old and risk of ischemic heart disease were investigated in 8 studies and 6 studies respectively.
Furthermore, 6 studies explored the relationship between hysterectomy and CVD. And 5 studies for association with ovarian preservation and CVD. Nine studies evaluated the relation between hysterectomy with oophorectomy and CVD. Six studies assessing the relationship between hysterectomy and hypertension were found. Four studies and three studies were respectively used to evaluate the association between hysterectomy with ovarian preservation and hypertension, and the relationship between hysterectomy with oophorectomy and hypertension. There are 5 studies included to assess the relation of hysterectomy and heart failure, 3 studies for arrhythmia and 8 studies for stroke. More details about the included studies were shown in Table S1.