Early Time-Restricted Eating, Circadian Alignment, and Cognitive Preservation in Older Adults: A Neurobiological Hypothesis

Nearly half of dementia cases are attributed to fourteen modifiable risk factors listed by the 2024 Lancet Commission; meal timing is not among them. Disrupted daily (circadian) rhythms are linked to faster neurodegeneration, yet it is unknown whether meal timing affects cognitive ageing. We review the evidence for the hypothesis that early time-restricted eating (eTRE) helps preserve cognition in older adults. We define eTRE as eating within a window of no more than 10 h, with at least 80% of daily energy eaten before 16:00. We evaluate three candidate pathways: daily rhythms in the removal of amyloid-beta and tau from the brain (glymphatic clearance), daily rhythms that keep brain inflammation low, and clock genes that support memory-related plasticity in the hippocampus. Nutrient-sensing and gut microbiota pathways are considered as alternatives. An AI co-scientist analysis, checked by the authors, suggested a “Dual-Gating” model: finishing meals early may lower nervous-system arousal and insulin levels at night, and both changes may favour brain clearance during sleep. We outline a three-arm trial (eTRE, late time-restricted eating, habitual eating) that tests whether any cognitive benefit is explained by changes in markers of clearance and inflammation. Meal timing remains a candidate exposure that needs prospective testing.