The study, presented recently at American Physiological Society annual meeting at Experimental Biology 2018 in San Diego, explores the association between hydration status before exercising and exercise-enhanced cognition in older adults.

Dehydration has been shown to impair exercise performance and brain function in young people, but less is known about its impact on older populations. “Middle-age and older adults often display a blunted thirst perception, which places them at risk for dehydration and subsequently may reduce the cognitive health-related benefits of exercise,” a team of New England-based researchers wrote.

The researchers recruited recreational cyclists (average age 55) who participated in a large cycling event on a warm day (78–86 degrees F). The cyclists performed a “trail-making” executive function test—quickly and accurately connecting numbered dots using paper and pencil—before and after the event. Executive function includes the skills needed to plan, focus, remember and multitask. Exercise has been shown to improve intellectual health, including executive function.

The research team tested the volunteers’ urine before they exercised and divided them into two groups—normal hydration and dehydrated—based on their hydration status. The normal hydration group showed noticeable improvement in the completion time of the trail-making test after cycling when compared to their pre-cycling test. The dehydration group also completed their post-cycling test more quickly, but the time reduction was not significant. “This suggests that older adults should adopt adequate drinking behaviours to reduce cognitive fatigue and potentially enhance the cognitive benefits of regular exercise participation,” the researchers wrote.