To determine whether systemic medical factors, such as vascular risk factors, metabolic and inflammatory markers contribute to cognitive decline in Parkinson’s disease (PD); if confirmed to determine whether a clinically applicable risk factor model can predict the conversion from normal cognition (NC) to mild cognitive impairment (MCI). 58 patients who met the UK Brain Bank Criteria for PD underwent clinical and laboratory assessment at study entry; 47 patients were re-assessed after 2 years. Medical history, vascular risk (QRISK2), blood metabolic and inflammatory factors, brain vessel examinations, activity of daily living, and neuropsychological testing were performed. Forty patients had NC and 18 patients had MCI at baseline. Patients with MCI had higher level of interleukin 6, folic acid below normal range and higher l-dopa equivalent dose compared to cognitive normal patients at baseline. Patients with NC at baseline were classified into two groups: patients who remained cognitively normal (non-converters, n = 23) and patients who progressed to MCI (converters, n = 11). MCI converters were older at baseline and had higher QRISK2 than the non-converters. Patients with higher QRISK2, lower uric acid level and lower activity of daily living scale at baseline had a higher risk of converting from NC to MCI with a sensitivity of 72.2%, a specificity of 87%, and an overall accuracy of 82.4%. Systemic medical factors are associated with cognitive impairment in PD both cross-sectionally and longitudinally. A risk factor model predicting the decline from NC to MCI could be constructed.
