Neuropsychiatric Inventory domains cluster into neuropsychiatric syndromes in Alzheimer's disease: A systematic review and meta‐analysis

Background: Studies of patients with Alzheimer's disease (AD) have observed that neuropsychiatric symptoms (NPS) tend to co‐occur as neuropsychiatric syndromes and have generally shown mixed results regarding the number and composition of syndromes. We systematically reviewed how neuropsychiatric syndromes in AD have been defined and compared the different published definitions in a pooled sample of AD patients using meta‐analytic structural equation modeling (MASEM). Methods: Studies examining the factor structure of the Neuropsychiatric Inventory (NPI) and published from 1994 to 2021 were included. We contacted the corresponding authors of eligible studies for correlation coefficients between NPI items. We pooled correlations under a random effects MASEM model and fitted and compared measurement models from published studies to identify a best‐fitting model. Results: Twenty‐five studies were included in the systematic review, and correlations were obtained from seven studies for MASEM. For the NPI‐10 (seven studies, n = 5185), a five‐factor structure was found to have a good fit to the data. For the NPI‐12 (four studies, n = 2397), we were unable to identify a factor structure that displayed a good model fit. Conclusion: This systematic review and meta‐analysis contribute to the development of a theoretical model of neuropsychiatric syndromes in AD and reveals the barriers that accompany MASEM methodology.