Beyond the one-size-fits-all hydration recommendation for older adults: a call for more research on age-related change in thirst and hydration behavior

In this perspective paper, I re-examine the evidence base behind the common advice that older adults should " drink plenty of water before feeling thirsty " especially during heat exposure and exercise. I first discuss the seminal mechanistic studies that have shaped current thinking, with particular attention to their dominant experimental paradigms. I then contrast this foundation with more recent studies quantifying ad libitum drinking during prolonged heat exposure or exercise in older vs. younger adults. Finally, I outline key research priorities needed to refine hydration guidance for aging populations. Overall, the aim is to prompt a more critical appraisal of long-standing assumptions and to highlight that our knowledge in this area remains surprisingly limited.