The DNA amplification multiples of DRP1 amplification significantly increased and the DNA amplification multiples of OPA1 amplification significantly decreased in the MCI and dementia groups compared with the normal group (DRP1: normal vs. MCI vs. dementia: 12.91 [8.3–27.91] vs. 30.71 [20.66–35.97] vs. 39.40 [33.56–88.16]; OPA1: normal vs. MCI vs. dementia: 0.90 [0.50–1.10] vs. 0.21 [0.16–0.45] vs. 0.15 [0.09–0.23]) (Fig. 2). This evidence concerns the gene OPA1 and dementia.