Chronic mild dehydration appears to function as an accelerant for biological aging processes, with serum sodium levels above 142 mmol/L correlating with shortened lifespan and increased disease burden in longitudinal cohort studies. The mechanism likely involves cellular stress responses and impaired protein folding that accumulate over decades of suboptimal hydration. This finding challenges the conventional wisdom that thirst is an adequate hydration guide for aging adults, whose thirst sensation diminishes with age while kidney function declines. The research suggests optimal hydration may be one of the most overlooked longevity interventions, potentially rivaling exercise and diet in importance for healthspan extension. However, the observational nature of current evidence leaves open whether dehydration is causal or merely correlated with poor health outcomes. Adults over 50 should consider monitoring urine color and frequency rather than relying on thirst cues, aiming for pale yellow output every 2-3 hours. The practical implication is profound: maintaining consistent fluid intake throughout the day may represent a simple, cost-free strategy for supporting healthy aging that most people currently underutilize.