APOE and dementia: Through multiple logistics regression analysis, we finally found that (1) the risk of mild cognitive impairment and dementia was significantly reduced in people who did not carry the APOE ε4 allele; (2) APOE ε4 carrying status may affect the impact of everyday life on cognitive decline; and (3) there was a significant interaction between APOE ε4 and sleep duration problems, both of which may contribute to cognitive impairment.