Predicting Cognitive Function in Mild Cognitive Impairment and Lewy Body Dementia: The Role of Neuropsychiatric, Motor, and Sleep Symptoms

Background Mild Cognitive Impairment (MCI) is often considered a prodromal phase of Lewy Body Dementia (LBD). While both conditions involve cognitive difficulties, they differ in the type and severity of non-cognitive symptoms. MCI is generally associated with mild cognitive changes and subtle neuropsychiatric, motor, and sleep disturbances. In contrast, LBD presents with more pronounced neuropsychiatric, motor, and sleep-related symptoms, which can affect cognitive performance. This study explores how these symptoms predict cognitive function in individuals with MCI and LBD, highlighting their distinct contribution to cognitive performance in each condition. Methods Data from N=36 patients with MCI, primarily Parkinson’s Disease-MCI (PD-MCI), and N=48 patients with LBD, including Parkinson’s Disease Dementia (PDD) and Dementia with Lewy Bodies (DLB) were analysed. Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory, sleep with the Epworth Sleepiness Scale, motor symptoms with the Hoehn and Yahr scale, and cognitive function with the Addenbrooke’s Cognitive Examination. Correlation and regression analyses explored the relationship between these factors and their role in predicting performance Results In the MCI group, neuropsychiatric symptoms were positively correlated with motor symptoms (p = 0.004). In the LBD group, neuropsychiatric (p < 0.001) and motor symptoms (p = 0.03) were significantly associated with lower cognitive functioning. Additionally, in LBD, neuropsychiatric symptoms were positively correlated with both motor (p = 0.02) and sleep symptoms (p < 0.001). In MCI, sleep symptoms significantly predicted poorer cognitive functioning (p = 0.03), whereas in LBD, neuropsychiatric symptoms were the strongest predictor of reduced cognitive functioning (p = 0.02), even after adjusting for age and gender. Conclusion Different patterns were observed in how neuropsychiatric, motor, and sleep symptoms influence cognitive functioning in the MCI and LBD groups, highlighting the distinct roles of non-cognitive symptoms in each condition. Early identification of these symptoms may offer valuable insights for monitoring cognitive functioning over time in these clinical populations.