Behavioral Changes May Emerge Years Before Cognitive Decline

Neuropsychiatric symptoms such as irritability, anxiety, and mood changes may follow distinct, measurable trajectories in the years before people develop mild cognitive impairment (MCI) and dementia, according to a new study published in Alzheimer’s Research & Therapy. The findings suggest that behavioral changes, often dismissed as normal aging or life stress, could serve as an early signal of underlying neurodegenerative disease.

Researchers analyzed data from 11,781 cognitively normal participants aged 60 or older drawn from the National Alzheimer’s Coordinating Center. Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory Questionnaire and domains derived from the Mild Behavioral Impairment framework. Using event-anchored models, the team tracked symptom trajectories relative to two key transitions: the shift from normal cognition to MCI, and the later progression from MCI to dementia. Among the full cohort, 2,865 participants developed MCI, and 731 of those subsequently developed dementia.

The results point to remarkably early separation between those who would later decline and those who would not. Overall neuropsychiatric symptom scores already differed at the earliest evaluated time point, 12 years before an MCI diagnosis, with a relative ratio of 1.42 (95% CI 1.09–1.84). Before dementia, symptom separation first became statistically significant 5 years ahead of diagnosis, with a relative ratio of 1.41 (95% CI 1.15–1.74). Both time points met the study’s prespecified acceleration criteria, although the researchers caution that the 12-year estimate sat at the boundary of the observation window, meaning the true onset of divergence could lie even earlier.

The timing differed across symptom domains. Emotional dysregulation showed the earliest sustained separation before MCI, while the acceleration of specific symptom domains preceding dementia was staggered, unfolding between 5 and 1 years before diagnosis. This staggered pattern hints that different behavioral symptoms may mark different stages of the neurodegenerative process, rather than emerging as a single uniform wave.

To probe the biology behind these trajectories, the team examined autopsy findings and cerebrospinal fluid (CSF) biomarkers. Neuropathological associations proved heterogeneous: links varied across Alzheimer Disease–Related Neuropathologic Measures, Lewy Body Pathology, and Cerebrovascular Pathologies, suggesting that no single pathology fully explains pre-diagnostic behavioral change.

The authors conclude that distinct nonlinear neuropsychiatric symptom trajectories precede both MCI and dementia and show heterogeneous neuropathological correlates. They note that longitudinal assessment of these symptoms may offer complementary information about behavioral progression, but they stress that the individual predictive value of such assessment still requires validation. In other words, while the population-level patterns are striking, the findings do not yet establish that tracking neuropsychiatric symptoms in a single person can reliably forecast who will develop MCI or dementia.

Subject of Research: Trajectories of neuropsychiatric symptoms preceding incident mild cognitive impairment and dementia

Article Title: Neuropsychiatric symptoms trajectories preceding incident mild cognitive impairment and dementia

Article References: Zhou, Z., Xiao, Y., Jin, M., Zhao, W., Qian, X., Wang, C., & Jia, F. (2026). Neuropsychiatric symptoms trajectories preceding incident mild cognitive impairment and dementia. Alzheimer's Research & Therapy. https://doi.org/10.1186/s13195-026-02228-9

Image Credits: AI Generated

DOI: 10.1186/s13195-026-02228-9

Keywords: neuropsychiatric symptoms, mild cognitive impairment, dementia, Alzheimer's disease, National Alzheimer's Coordinating Center, p-tau, Lewy body pathology, cerebrovascular pathology, mild behavioral impairment, CSF biomarkers, Neuropsychiatric, symptoms