Longitudinal association between multimorbidity, cognitive decline and neuropsychiatric symptoms

Abstract Background Alzheimer’s disease (AD) is the most common form of dementia afflicting more than 5.8 million older adults in the United States. In AD, cognitive decline and neuropsychiatric symptoms are more pronounced in those who have chronic conditions. These chronic conditions often co‐occur with other chronic conditions, known as multiple chronic conditions (MCCs). This study aimed to examine the longitudinal association between the number of chronic conditions with cognition and neuropsychiatric symptoms by cognitive status. Methods Participants were 21,219 community dwelling individuals from the longitudinal National Alzheimer’s Coordinating Center (NACC, U24 AG072122) database (mean age = 71.8 ± 9.8; 42.8% male). Participants completed a medical history interview, cognitive assessment, and the Neuropsychiatric Inventory (NPI), approximately every two years over a 15‐year period. Number of MCCs was characterized as the sum of clinician‐diagnosed chronic conditions (i.e., cardiovascular, metabolic, sleep, respiratory, and psychological conditions;range 0‐18). The analysis focused on memory (Craft Story 21 recall immediate and delayed), processing speed (Trails A), and executive function (Trails B, Coding, animal naming). We used mixed effect models to test whether the number of MCCs was associated with a change on each cognitive test and number neuropsychiatric symptoms by clinician diagnosed cognitive status (i.e., normal cognition, mild cognitive impairment (MCI) presumed AD etiology, MCI presumed without AD etiology, MCI with AD etiology, dementia with AD etiology, dementia with non‐AD etiology). Results We found that the mean number of chronic conditions were, 2.2 ± 1.8 in cognitively normal individuals, 2.8 ± 2.0 in MCI with AD etiology, 2.8 ± 2.0 in MCI with non AD etiology, 2.7±1.9 in dementia with AD etiology, 3.0±2.1 in dementia with non‐AD etiology. Compared to cognitively normal adults, individuals with more severe cognitive impairment (i.e., groups with dementia) and a higher number of MCCs demonstrated greater decline in immediate and delayed memory recall, Trails A, animal naming, and coding (p <0.05), as well as the number of neuropsychiatric symptoms (p <0.05) over time accounting for age, sex, and education. Conclusion The findings suggest that having a higher number of chronic conditions is associated with longitudinal decline in cognition and neuropsychiatric symptoms.