DLG4 and Alzheimer disease: The results of the subgroup analysis showed that exercise before AD had a greater effect on escape latency (SMD = -0.88, 95% CI: -1.25 to -0.52, <i>P</i> < 0.001), platform crossover numbers (SMD = 1.71, 95% CI: 1.23-2.18, <i>P</i> < 0.001), time in the target quadrant (SMD = 2.03, 95% CI: 1.19-2.87, <i>P</i> < 0.001) and the expression of PSD95 (SMD = 0.94, 95% CI: 0.19-1.69, <i>P</i> = 0.014) than exercise after AD.