Cognitive and Motor Decline in Dementia with Lewy Bodies and Parkinson's Disease Dementia

ABSTRACT Background There is a need to better understand the rate of cognitive and motor decline of Dementia with Lewy bodies (DLB) and Parkinson's disease Dementia (PDD). Objectives To compare the rate of cognitive and motor decline in patients with DLB and PDD from the E‐DLB Consortium and the Parkinson's Incidence Cohorts Collaboration (PICC) Cohorts. Methods The annual change in MMSE and MDS‐UPDRS part III was estimated using linear mixed regression models in patients with at least one follow‐up (DLB n = 837 and PDD n = 157). Results When adjusting for confounders, we found no difference in the annual change in MMSE between DLB and PDD (−1.8 [95% CI −2.3, −1.3] vs. −1.9 [95% CI −2.6, −1.2] [P = 0.74]). MDS‐UPDRS part III showed nearly identical annual changes (DLB 4.8 [95% CI 2.1, 7.5]) (PDD 4.8 [95% CI 2.7, 6.9], [P = 0.98]). Conclusions DLB and PDD showed similar rates of cognitive and motor decline. This is relevant for future clinical trial designs.