MMP9 and hyperlipidemia: The differences between the three groups were statistically significant in age, hypertension, hyperlipidemia, glucose levels, serum CyPA levels, serum MMP-9 levels, NDE Aβ42 levels, WMH volume, total CSVD burden scores, AHI, arousal index, mean SaO2, T90, time ratio of N1, and time ratio of N3 (P = 0.027, P = 0.004, P = 0.028, P = 0.001, P = 0.006, P = 0.003, P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, respectively) by using one-way ANOVA tests, Kruskal-Wallis H test, or χ2 test.