Water and Executive Function

Though it’s technically September, many of us are still reeling from one of the hottest summers on record. Everyone knows a hot day can be hard to handle; it’s sweaty, bright, and all around uncomfortable for many. Did you know that heat is also affecting your executive function? It’s not the glare in your eyes from the sun that’s causing the problem—thirst is to blame.

Extreme heat often leads to dehydration as the body sweats out moisture to stay cool. A recent study by Matthew Wittbrodt and Mindy Millard-Stafford at Georgia Tech found that even mild dehydration can impact executive function, attention, and motor coordination.

The study examined the performance of participants as they completed both mental and physical tests after being dehydrated. Subjects experienced dehydration from a variety of causes, including exercise in heat, exercise online, heat stress with exercise, or fluid restriction.

Though there was some variation between the causes of dehydration, evidence showed that across all cases dehydration had a negative effect on executive function performance.

These deficits were most notable once dehydration passed 2% loss of body mass. Willbrodt explains, “A distinct sensation of thirst appears as body water losses approach 2% body mass loss… Thus, if someone feels thirsty, they are likely within the range of dehydration we found results in cognitive impairment.”

Dehydration may be a major risk in the summer, but it’s a threat year round. A study by Erica Kenney and colleagues at Harvard’s T.H. Chan School of Public Health estimated that 25% of school-age students don’t drink any water at all, relying on sports drinks and soda to fill the gap, meaning they are at constant risk of being at least mildly dehydrated, with consequences for their academic achievement.

So what’s the answer? I’m not arguing that you should keep your students indoors and out of the sun or stop them from playing sports and exercising, especially when some sports are shown to boost executive function. Instead, we need to be aware of the importance of hydration.

Schools should provide students with easy access to clean, fresh drinking water. (One can only imagine the negative academic impact on students in Detroit schools who had their water turned off due to contamination with lead and copper.) Instead of discouraging bathroom breaks with threats and punishments, teachers should encourage their students to drink water if they want to really see what their students can do. Keeping students hydrated will help them perform to their ability.

  • Michael Greschler, M.Ed., SMARTS Director