Trajectories of Cognitive Functioning in Older Age Bipolar Disorder

OBJECTIVES: The prevalence of cognitive impairment is high in older age bipolar disorder (OABD). It remains unclear whether the course of cognitive functioning in these individuals follows a course of cognitive decline, whether this is different among subgroups, and if so, which factors are associated with cognitive decline. METHODS: Our clinical sample included 206 patients aged over 50 years from the Dutch Older Bipolar (DOBi) cohort with a total range of included measures of 306 months (1997-2022). Growth Mixture Modeling (GMM) was used to find homogeneous subgroups based on their longitudinal trajectories of the Mini-Mental State Examination (MMSE) scores. Patients were categorized in classes based on similar trajectories, and these classes were compared based on their performance on nine cognitive tests using mixed models. RESULTS: Three classes could be identified through GMM, each demonstrating a modest, parallel decline in MMSE scores: one class showed consistently high cognitive performance; another with moderate cognitive functioning; and a third group with significant cognitive impairment. Multivariate analyses showed that an advanced age at baseline and an earlier onset of the disorder were predictive of a more impaired cognitive trajectory. Furthermore, nine supplementary cognitive assessments demonstrated pronounced disparities across these three groups, with the most substantial cognitive deficits in individuals with the most unfavorable MMSE trajectories. DISCUSSION: Our findings underscore the heterogeneous nature of cognitive aging in OABD, revealing a spectrum of cognitive longitudinal trajectories. Findings indicate that the MMSE is a valid screener in order to broadly predict cognitive functioning and its course in OABD. Identifying individuals who are particularly susceptible to cognitive decline is crucial for initiating tailored rehabilitation strategies.