Hypothesis-Generating Brief: Cognition Durations — full paper

Researka accepted publication: ff0b0ca6-f6d9-4aba-9607-9ac47683763a Source submission: c4a57e47-0b2a-496a-92e5-e48b1b1d6feb Evidence-honesty note: 12/14 retained sources are indirect, review-level, adjacent, or mechanistic and are used only to bound interpretation. The conclusion therefore does not support broad causal, clinical, or policy claims. The optimal duration of sleep, exercise, and structured intervention windows for preserving cognition in older adults remains unresolved, despite the centrality of these exposures to healthy-aging policy. Operationally, this synthesis scopes "Cognition Durations" to time-varying behavioral and clinical exposures whose dose — hours of sleep, minutes of exercise, or weeks of intervention follow-up — plausibly modifies cognitive endpoints, while explicitly excluding pharmacology dosing and non-behavioral time variables. We conducted an AI-assisted structured evidence synthesis across 14 curated human-aging studies, with every included citation tied to an auditable source describing design, outcome class, directness tier, and effect direction; cross-domain tensions between mechanistic and clinical evidence, and between direct and indirect anchors, were preserved rather than collapsed. Across the source set, context-specific cognitive signals cluster in reviews of exercise dosing (Yang 2026) and in Parkinson's-disease mediation work (Cui 2026, P < 0.