CCL2 and Alzheimer disease: When comparing AD with MCI, however, the CSF CCL2 (MCP-1) concentrations did not differ substantially (RoM, 1.04, 95% CI, 0.90–1.19, corrected p = 1.893; I2 = 56.3%; Fig. 4), suggesting that CSF CCL2 appears to be a marker reflecting the degree of cognitive impairment, although it has a slight elevation.