Study characteristics
Among the 2134 articles retrieved from the databases, 116 articles were finally screened: 96 Chinese articles (Supplementary) and 20 English articles17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36. The articles included a total of 23,396 patients with AD and 25,568 control individuals. Figure 1 depicts the literature screening process. The study area source distribution was as follows: a total of 115 studies clearly identified the specific source of cases covering 28 provincial-level regions (Fig. 2). Another multicentre study, which could not be consolidated, covered 30 provincial-level regions21. Fifty-one of the studies reported the age distribution of the subjects (Fig. 3). In conclusion, the case sources in this meta-analysis covered at least 30 provincial-level administrative regions (including Taiwan and China) out of 34, with good…
