The spectrum of bipolar disorder in older adults.

The absolute number and relative proportion of individuals with older-age bipolar disorder (OABD) is expected to rise due to the global aging of the population, necessitating a greater understanding of the unique characteristics of OABD and the trajectory of aging with BD in order to improve the health span of people with BD. This review summarizes current knowledge on OABD, examining its clinical presentation, neurobiology, and treatment, as well as identifying key gaps and future directions for research. OABD is characterized by relatively greater cognitive impairment and somatic burden, despite potentially reduced mood symptom severity compared to younger-age bipolar disorder (YABD). This significantly impacts functional outcomes in older age, highlighting the need for age-adjusted clinical strategies. Individual differences in illness course, treatment history, and psychotic features influence the clinical presentation and prognosis in OABD. One powerful strategy to better understand OABD is to bring together existing data from across the globe through large-scale collaborations. In the realm of BD, this is exemplified by several ongoing efforts including the Global Aging and Geriatric Experiments in Bipolar Disorder (GAGE-BD) initiative and the Enhancing NeuroImaging Genetics through Meta-Analysis Bipolar Disorder (ENIGMA-BD) working group. Evidence on the trajectory of bipolar disorder (BD) across the lifespan is mixed, with some individuals showing accelerated cognitive and biological aging. Biomarker studies reveal overlaps between YABD and OABD, but also suggest age-specific alterations in inflammation and oxidative stress pathways. Lithium remains a first-line pharmacological treatment in OABD, with emerging evidence supporting other pharmacologic and behavioral interventions, although large-scale, age-specific trials remain limited. Neuromodulation treatment approaches appear promising but remain relatively unexplored in OABD. The review highlights current knowledge gaps, particularly the need for longitudinal research to identify early predictors of impairment, and to guide potential preventative strategies. This summary emphasizes the potential of global consortia and multi-center studies to deepen insights into BD aging trajectories with high generalizability. Ultimately, a lifespan approach that incorporates lived experience, early intervention, and global collaboration is essential to promoting health and well-being in individuals with OABD.