Trajectories of subjective cognitive decline, and the risk of mild cognitive impairment and dementia

Background In cognitively‐normal individuals, subjective cognitive decline (SCD) has been reported to predict MCI and dementia (MCI/dementia). However, prior studies mostly captured SCD at single time‐points without considering the longitudinal course of SCD. This study examined whether the trajectories of SCD provide any added information – beyond one‐time assessments of SCD – on the risk of MCI and dementia (MCI/dementia). Method This cohort study included 5,661 participants from the Alzheimer’s Disease Centers across USA, who were ≥50 years and had normal cognition in the first‐four annual visits (Year 1 to Year 4). The participants were evaluated for SCD in the first‐four annual visits (Year 1 to Year 4), and followed‐up almost annually (from Year 4 up to Year 14) for incident MCI/dementia. SCD trajectories – as identified from latent‐class‐growth‐curve‐analysis – were included in Cox‐regression to estimate their risks of MCI/dementia. Result Compared to those without SCD (in the first‐four annual visits), the presence of Intermittent SCD (i.e. reported in 1–2 of the first‐four annual visits) predicted a higher risk (HR 1.4) while Persistent SCD (i.e. reported in 3–4 of the first‐four annual visits) predicted the highest risk (HR 2.2). A quarter of those with Persistent SCD developed MCI/dementia within 4.7 years; in contrast to 5.8 years among those with Intermittent SCD , and 8.0 years among those without SCD. The results remained significant even after adjusting for baseline SCD. Conclusion The findings demonstrate the added utility of SCD trajectories – beyond cross‐sectional assessments of SCD – in identifying high‐risk populations for preventive interventions and trials. They also suggest a potential modification in the current SCD criteria, with the inclusion of ‘persistent SCD over several years’ as one of the key features within SCD plus .