Paths of Aging Minds: Health Journeys of Older Adults with Mild Cognitive Impairment

Abstract Background: Mild cognitive impairment (MCI) is often conceptualized as an intermediate stage between normal cognition and dementia. However, emerging evidence suggests that cognitive status may change bidirectionally, with individuals experiencing reversion to normal cognition, persistent impairment, or progression to dementia. Previous studies have focused on single transitions or clinical samples frequently. This study aimed to characterize dynamic transitions among normal cognition, MCI, and dementia following incident MCI using longitudinal population-based data. Methods: We conducted a retrospective cohort study using data from the Health and Retirement Study (HRS) from 1992 to 2022. Cognitive status was classified at each biennial assessment using the Langa-Weir cognitive classification based on the modified TICS and proxy assessments. Incident MCI was defined as a transition from previously observed normal cognition to MCI. Participants were followed for up to five subsequent HRS waves (approximately 10 years). Descriptive statistics were used to describe changes of cognitive status between waves. A continuous-time multistate Markov model wase used to estimate transition intensities and transition probabilities among normal cognition, MCI, and dementia, including both progression and reversion. Results: Among 10,489 participants with incident MCI, the mean age at the incident MCI wave was 70.6 years (SD = 11.53), and 56.6% were female. Two years after incident MCI, 62.3% of observed participants were classified as having normal cognition, 31.2% remained in MCI, and 6.5% were classified as having dementia. At 4, 6, 8, and 10 years after incident MCI, the proportion classified as normal cognition declined while the proportion of participants with dementia increased. The multistate model demonstrated substantial bidirectional movement among cognitive states. The estimated transition intensity from MCI to normal cognition was 0.453 (95% CI 0.443–0.463), compared with 0.126 (95% CI 0.121–0.131) for MCI to dementia. Transitions also occurred from normal cognition to MCI (0.265; 95% CI 0.257–0.273) and dementia (0.037; 95% CI 0.035–0.041), as well as from dementia to MCI (0.226; 95% CI 0.209–0.245) and normal cognition (0.064; 95% CI 0.055–0.074). Conclusions: Cognitive trajectories following incident MCI were heterogeneous and dynamic, involving reversion, persistence, progression, and recurrent transitions among cognitive states. These findings support a multistate conceptualization of cognitive aging rather than a predominantly unidirectional model of progression toward dementia. Although reversion in cognitive classification should not be interpreted as definitive biological recovery, its frequent occurrence highlights the importance of repeated longitudinal assessment and further investigation of factors associated with cognitive resilience and dementia risk.