Long term cognitive outcome of prodromal and mild dementia with Lewy bodies: a cohort study

The cognitive evolution of early dementia with Lewy bodies (DLB) is less well known than that of Alzheimer's disease (AD). During dementia, DLB progresses like AD. The aim of this study was to analyze the long-term cognitive decline of early DLB. Participants were recruited for either mild cognitive impairment or mild dementia with a suspicion of DLB or AD, or as healthy older subjects (AlphaLewyMA study, NCT01876459, 2013). Using beta regression, we compared the slope of the Mini-Mental State Examination (MMSE) score of 110 DLB patients (DLB group), 57 AD patients (AD group), 19 DLB and AD patients (DLB + AD group), 30 patients with other cognitive diseases (DC group), and 31 healthy older controls (HC group). The mean follow-up was 4.8 years. All patients' groups had a significant decrease in MMSE score. The slope of MMSE decline of the DLB group (-0.49 point a year) was higher than the HC group (+ 0.03; P < .0001), lower than that of the AD (-2.78; P < .0001) and DLB + AD (-2.92; P < .0001) groups and not different from the DC group (-0.29; P = .8000). The variability of annual variations in MMSE score was greater in the DLB group (2.13 points) than in the AD group (1.73 points). There was no difference between patients' group in terms of death or admission to a nursing home. Patients with early DLB decline cognitively more slowly while fluctuating, whereas AD and DLB + AD patients decline markedly. These results suggest that there is a more dysfunctional than neurodegenerative phase at the beginning of DLB.