No gene-by-environment interaction between APOE and PA in cognitive decline was found in multiplicative scale (APOE × moderate PA: OR = 1.03, 95% CI: 0.80–1.33; APOE × high PA: OR = 1.02, 95% CI: 0.78–1.32) and there was no heterogeneity between studies (APOE × moderate PA: I2 = 0.0%, p = .79; APOE × high PA: I2 = 0.0%, p = .66; Figure 3). This evidence concerns the gene APOE and Mental deterioration.