APOE and Alzheimer disease: After adjusting for APOE ε4 mutations, there was no statistically significant difference in the risk association between DM and AD (HR = 1.07, 95% CI (0.97-1.19), <i>P</i> = 0.177), whereas without adjustment for APOE ε4 mutation, DM was associated with an increased AD risk (HR = 1.42, 95% CI (1.23-1.64), <i>P</i> < 0.00001).<h4>Conclusion</h4>This meta-analysis provides compelling evidence that DM is an independent risk factor for AD, offering important implications for clinical practice and future research.