[Dementia with Lewy bodies and Parkinson disease dementia, their diagnoses and treatment strategies].

Parkinson's disease (PD), which has characteristic motor symptoms such as tremor, muscle rigidity, and akinesia, and as the disease progresses, Lewy bodies spread throughout the brain, eventually causing Parkinson disease dementia (PDD). The clinical picture of PDD is similar to Dementia with Lewy bodies (DLB) and their pathological features are indistinguishable from each other. More than 80% of PD cases will eventually develop dementia and their prognosis are generally 3 to 4 years from the onset of dementia, regardless of disease duration or age of onset. We found that patients with severe olfactory impairment had lower cognitive function scores, more frequent onset of dementia, brain atrophy, and prominent cerebral metabolic abnormalities in a 3-year longitudinal study (Brain 135:161-169, 2012). This study demonstrated for the first time in the world that olfaction tests are useful in predicting dementia in PD, and similar results have been followed up worldwide. Based on these results, a randomized, double-blind, multicenter comparative study of donepezil in PD with severe olfactory dysfunction (DASH-PD study) was conducted and completed a 4-year follow-up period. The results were recently published showing the efficacy and safety of cholinesterase inhibitors for PD without dementia (eClinicalMedicine 51: 101571, 2022).