Hyperuricemia as a Protective Factor for Mild Cognitive Impairment in Non-Obese Elderly

Mild cognitive impairment (MCI) is regarded as incipient dementia. Patients with MCI have increased risk of later progressing to dementia. Blood uric acid (UA) is an important non-enzymatic antioxidant in peripheral circulation, and plays an unconfirmed protective role in MCI. Furthermore, obesity-induced inflammation, which affects UA metabolism and MCI onset, might regulate such protective role. Thus, the aim of the study was to determine the relationship of UA to MCI and the potential effect from inflammation. The study consisted of 933 MCI patients diagnosed by neuropsychological scales and 933 controls with normal cognitive function. All subjects were ≥ 60 years old. There were 378 obese subjects in MCI group and 410 obese subjects in control group. A relationship between lower serum UA levels and higher risk of MCI was found in all MCI patients and non-obese MCI patients (OR: 0.78, 95% CI: 0.72 ~ 0.86; OR: 0.66, 95% CI: 0.55 ~ 0.78), but not in obese MCI patients (OR: 0.94, 95% CI: 0.81 ~ 1.12). Serum UA and hypersensitive C reactive protein (hs-CRP) levels were higher in obese MCI patients than in non-obese MCI patients (P < 0.001 and P < 0.001). Serum UA levels showed a positive linear correlation with serum hs-CRP levels in obese MCI patients (r = 0.284, P < 0.001), but not in non-obese MCI patients (r = 0.030, P = 0.481). In conclusion, we show the significant association between lower serum UA levels and higher risk of MCI in non-obese subjects. Obesity-induced inflammation may weaken such relationship.