Parkinson's disease dementia and dementia with Lewy bodies – epidemiology, risk factors and biomarkers

Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are common and debilitating dementia syndromes accompanied by Parkinsonism and a range of other psychiatric, sleep and autonomic disturbances. Disease mechanisms are unknown, but aggregated Lewy bodies containing alpha-synuclein are believed to play a central role in the pathogenesis. Point-prevalence of dementia in Parkinson's disease (PD) is approximately 30%, and the majority develop dementia as the disease progresses. Recent studies suggest that 25-30% of non-demented PD patients have mild cognitive impairment (MCI), and 15-20% already have it at the time of the diagnosis. PD-MCI is a strong predictor of PDD. There are few welldesigned epidemiological studies of DLB, but available evidence suggests that 15-20% of the total dementia population have DLB. Predicting future cognitive impairment is a priority, but the pre-dementia stage of DLB is essentially unexplored. Promising biomarkers are being researched, but, given the complexity of this disease, a multimodal approach is more likely to permit diagnostic precision in the future.