In AD, the degree of region-specific synapse loss better correlates with cognitive decline than amyloid plaques, NFTs and neuron loss (173, 174) and genetic variants of complement receptor 1 (CR1) and clusterin (CLU, apolipoprotein J), which are parts of the complement system, are identified as AD risk factors by genome wide association studies (175). This evidence concerns the gene CR1 and Alzheimer disease.