Compared with that in the NC group (1.65±0.35 ng/μL), the serum IL-6 levels in the MCI group (2.02±0.56 ng/μL) and the AD group (3.58±0.98 ng/μL) were significantly up-regulated (P< 0.05), as shown in Figure 2, and the serum Aβ1-42 level in the MCI group was significantly up-regulated (P< 0.05); that in the AD group was also up-regulated, but the difference was not significant (P> 0.05). Here, IL6 is linked to Alzheimer disease.