Parallel associations between cognitive and neuropsychiatric symptom domains in older adults

TL;DR

This study finds that as cognitive abilities decline in early Alzheimer's disease, neuropsychiatric symptoms like mood and impulse control tend to increase over time.

Contribution

The study reveals longitudinal associations between specific cognitive and neuropsychiatric symptom domains in early-stage Alzheimer’s disease.

Findings

Cognitive decline is associated with increasing neuropsychiatric symptoms over 48 months.

Impulse dyscontrol shows a stronger longitudinal link with language than with other cognitive domains.

Mood and somatic disturbance symptoms correlate similarly with cognitive decline across domains.

Abstract

Despite the high prevalence of neuropsychiatric symptoms (NPS) in those with Alzheimer’s disease and Alzheimer’s disease-related dementias (AD/ADRD), longitudinal research examining the co-occurrence of NPS and cognition has been underexplored, especially during earlier stages of the disease. Our study aimed to investigate the co-occurring trajectories between specific domains of NPS and cognition in those with preclinical or prodromal AD/ADRD. Participants were 1,255 individuals from the Alzheimer’s Disease Neuroimaging Initiative (ADNI)-2 and ADNI-3 cohorts who were cognitively normal (CN) or had mild cognitive impairment (MCI) at baseline. This cohort was evenly split by sex and was predominantly White and non-Hispanic. Parallel process models were used to examine how a change in cognition was associated with a change in NPS as measured by the Neuropsychiatric Inventory (NPI) over 48 months. We ran 9 models total to examine relationships between 3 cognitive domains (memory, executive function, and language) and 3 NPS domains (impulse dyscontrol, mood, and somatic disturbance). Cognitive domain and NPS slopes were negatively correlated in each model, such that as cognition decreased, NPS increased. Follow-up testing using Steiger’s z-test to compare the correlations across domains suggested no significant differences in the strength of the relationship between mood or somatic disturbance with cognition across domains. However, impulse dyscontrol had a significantly stronger relationship with language than with other cognitive domains. These findings extend prior cross-sectional work that found communication-impulse dyscontrol behavior (e.g., aggression) associations to demonstrate strong co-occurrence longitudinally in those with early-stage AD/ADRD.