Decline in everyday function is a hallmark of dementia and is associated with increased caregiver burden, medical spending, and poorer quality of life. Neuropsychiatric symptoms (e.g., apathy, hallucinations) can also occur in those with dementia and have been associated with worse everyday functioning cross-sectionally. However, research on which neuropsychiatric symptoms are most associated with everyday functioning in those with dementia longitudinally has been more limited. Further, it is unknown which neuropsychiatric symptoms may add incremental validity beyond cognition in predicting everyday function longitudinally. The current study aimed to address both of these gaps in the literature by identifying which neuropsychiatric symptoms are most associated with everyday function over time and if symptoms add incremental validity in predicting everyday function beyond cognition in those with dementia.

Older adult participants (N = 4525), classified as having dementia at baseline by the National Alzheimer's Coordinating Center, were examined. Severity of neuropsychiatric symptoms were measured via the Neuropsychiatric Symptoms Questionnaire-Informant. Everyday function was assessed via the Functional Activities Questionnaire-Informant. Memory (Logical Memory immediate and delayed) and executive function (Digit Symbol Test, TMT-A and TMT-B) composites were created to assess cognition. Severity of neuropsychiatric symptoms at baseline were analyzed as predictors of everyday functioning beyond demographic factors and cognition at baseline and over the course of five years using multilevel modeling.

At baseline, severity of the majority of symptoms, excluding irritability, manic symptoms, and changes in appetite, were associated with everyday function (all p < .05). When examining everyday functioning longitudinally, only severity of hallucinations, apathy, motor dysfunction, and sleep dysfunction were associated with differences in everyday function over time (all p < .01).

There is heterogeneity in the degree to which neuropsychiatric symptoms are associated with everyday functioning over time in those with dementia. Additionally, our results show that some neuropsychiatric symptoms are associated with longitudinal changes in everyday function beyond domains of cognition show to be associated with function. Clinicians should pay particular attention to which neuropsychiatric symptoms individuals with dementia and their families are reporting to aid with treatment planning and clinical decision making related to autonomy. Future research would benefit from examining pathways through which neuropsychiatric symptoms are associated with everyday functioning over time in this population, and if treatments of neuropsychiatric symptoms may improve everyday function in this population.