Consistent with the trend in CSF, serum SV2A levels also progressively decreased with the progression of dementia, as evidenced by a significant reduction in the mean serum SV2A levels of approximately 55.32% (p < 0.0001) and 74.94% (p < 0.0001) in aMCI and AD, respectively, relative to controls, and a significant reduction of approximately 43.92% (p < 0.0001) in AD relative to aMCI (Fig. 2d). Here, SV2A is linked to Alzheimer disease.