A study published in JAMA Network Open examined salivary cortisol patterns over an 11-year span and found that both an irregular daily rhythm and consistently elevated cortisol levels were linked to cognitive decline in later years. The research adds to evidence that stress hormones may serve as early indicators of cognitive aging.
The study also reported a notable difference by race: Black participants had lower overall cortisol levels and less pronounced irregularity compared to other groups. However, the source does not specify whether this difference altered the association with cognitive decline, leaving that question open.
Because this is a single observational study, the findings point to a correlation rather than a proven cause. Further work would be needed to determine whether cortisol patterns can reliably predict individual cognitive trajectories or guide interventions.