Predicting cognitive decline using neuropsychiatric symptoms in prodromal Lewy body disease

Abstract:

AbstractBackgroundNeuropsychiatric symptoms (NPS) in Lewy body diseases, including dementia with Lewy bodies (DLB) and Parkinson’s disease (PD) dementia, occur frequently and at an early stage in disease progression. Such symptoms are significantly associated with quality of life, caregiver burden and functional limitations. Limited evidence exists, however, outlining the relationship between NPS and cognitive decline.MethodsData from 217 participants were derived from three cohort studies. Patients diagnosed with either MCI with Lewy bodies (MCI‐LB, n = 67), PD‐MCI (n = 56) or Alzheimer’s disease (MCI‐AD, n = 39) and a group of healthy older adults (n = 55) completed comprehensive neuropsychological and neuropsychiatric assessment and were followed up longitudinally for a median of three years. NPS identified at baseline by the Neuropsychiatric Inventory (NPI) were included as predictors in linear regressions and linear mixed effects models to assess the relationship between NPS and performance on a range of cognitive tests both at baseline and longitudinally.ResultsAt baseline, NPS were most prevalent and severe among the MCI‐LB group (49% with NPI score >4 in at least one symptom) and least prevalent in controls (7% with NPI score >4). Total NPI score was not related to baseline cognitive function in any domain in any group. Greater baseline total NPI score was associated with steeper rates of decline among PD‐MCI patients on a measure of processing speed (p = .01). Among healthy adults, only sleep disturbance was associated with steeper rates of decline on global cognition (p = .005). None of the patient groups showed any association between individual NPS and decline on a measure of global cognitive function.ConclusionsThe lack of a significant relationship found between NPS and either global cognitive function or decline in global cognition seen among MCI patients suggests that at this prodromal stage of disease, NPS appear to be of limited clinical impact and indicates that the mechanisms of cognitive and neuropsychiatric symptoms may differ in early Lewy body disease. Future work will investigate these mechanisms using multimodal imaging data from this cohort.