Precisely, the CSF complement protein levels were obviously lower in the A + individuals than in A − individuals and the A + T + group had significantly lower levels of CSF complement proteins compared to A + T − and A − T − groups; (2) lower complement protein levels might contribute to faster cognitive decline and atrophy of multiple brain regions in the MCI population; (3) mediation studies showed that whole brain volume, regional ventricular, middle temporal, or fusiform volume mediated the association between low levels of CSF complement proteins and accelerated cognitive decline. The gene discussed is VTN; the disease is Mental deterioration.