The influence of white matter hyperintensity on cognitive impairment in Parkinson's disease

The aim of this meta-analysis was to review systematically and to identify the relationship between the severity and location of white matter hyperintensities (WMHs) and the degree of cognitive decline in patients with Parkinson's disease (PD). We searched the PubMed, EMBASE, Web of Science, Ovid, and Cochrane Library databases for clinical trials of the severity and location of WMHs on the degree of cognitive impairment in PD through October 2020. We conducted the survey to compare the association of WMH burden in patients with PD with mild cognitive impairment (PD-MCI) versus those with normal cognition (PD-NC) and in patients with PD with dementia (PDD) versus those with PD without dementia (PD-ND). Nine studies with PD-MCI versus PD-NC and 10 studies with PDD versus PD-ND comparisons were included. The WMH burden in PD-MCI patients was significantly different compared to that in PD-NC patients (standard mean difference, SMD = 0.39, 95% CI: 0.12 to 0.66, p = 0.005), while there was no correlation shown in the age-matched subgroup of the comparison. In addition, PDD patients had a significantly higher burden of WMHs (SMD = 0.8, 95% CI: 0.44 to 1.71, p < 0.0001), especially deep white matter hyperintensities (SMD = 0.54, 95% CI: 0.36 to 0.73, p < 0.00001) and periventricular hyperintensities (SMD = 0.70, 95% CI: 0.36 to 1.04, p < 0.0001), than PD-NC patients, regardless of the adjustment of age. WMHs might be imaging markers for cognitive impairment in PDD but not in PD-MCI, regardless of age, vascular risk factors, or race. Further prospective studies are needed to validate the conclusions.