Stability of the factor structure of the Neuropsychiatric Inventory in a 31-month follow-up study of a large sample of nursing-home patients with dementia

Abstract

Neuropsychiatric symptoms (NPS) are highly prevalent among nursing home patients with dementia. Several studies have investigated subsyndromes of NPS but the stability of these subsyndromes over time has rarely been examined. We have examined the stability over time of the factor structure of the Neuropsychiatric Inventory-Nursing Home version (NPI-NH) in a large sample of nursing-home patients with dementia. Nursing-home patients with dementia were assessed with the NPI-NH at baseline (n = 895), and at 12-month (n = 592) and 31-month (n = 278) follow-up assessments, giving three partly overlapping samples. Exploratory factor analysis was done to investigate neuropsychiatric subsyndromes of the NPI-NH at each assessment in these samples. Three- or four-factor solutions were found, termed agitation, psychosis, apathy, and affective symptoms. Depression and anxiety (affective), delusion and hallucination (psychosis), and agitation and irritability (agitation) were the symptoms that most often co-occurred in the same factor. Apathy did not load together with affective symptoms at any of the assessments. Subsyndromes of the NPI-NH are relatively stable over 31-month follow-up assessments in nursing-home patients with dementia, indicating that these subsyndromes may be useful for following the natural course of symptoms as well as observing the effect of interventions. Our findings lend support to the distinction between apathy and affective symptoms, which may have important clinical implications.