Adequate hydration
Mild chronic dehydration is common; 'pale yellow urine' is the simplest gauge.
Why
Mild chronic dehydration is associated with worse cognitive performance and faster cognitive decline. The 8-glass rule is folklore; actual needs vary by climate, body size, and activity. Urine colour is the simplest marker, pale straw to pale yellow is fine.
Slot in your day
How to do it
How
Drink to thirst plus a glass on waking. Pale-yellow urine = adequate. Increase in heat and during exercise.
Markers this may influence
Evidence
Nishi 2023 BMC Medicine prospective cohort (n=6,874): higher hydration biomarkers (serum osmolarity in the optimal range) were associated with slower cognitive decline over follow-up. The 8-glass rule is folklore, urine colour (pale straw to pale yellow) is the simplest practical marker. Effect direction is consistent but absolute magnitude is modest.