Struggling to Concentrate? It Might Be Dehydration, Study Says

A man drinks from a water bottle in the northern French city of Lille on July 25. The National Academies of Science, Engineering, and Medicine suggests that men, on average, should consume around 125 ounces of water a day. DENIS CHARLET/AFP/Getty Images

Even mild dehydration can negatively affect your cognitive performance, according to a new meta-analysis of existing research published in the journal Medicine & Science in Sports & Exercise.

Researchers from the Georgia Institute of Technology examined the results of more than 30 studies looking at dehydration. They found that just a small deficit of total body water can impair our mood and our thinking, especially when it comes to tasks that require complex processing or significant amounts of concentration.

"The previous literature on this topic is extremely mixed as to whether dehydration impairs cognitive performance," Mindy Millard-Stafford, director of the Exercise Physiology Laboratory at Georgia Tech's School of Biological Sciences and a co-author of the study, told Newsweek. "By utilizing a meta-analytical approach, we attempted to provide an objective summary of this previous work."

"The key finding was that dehydration impaired cognitive performance," she said. "Specifically, we found tasks involving executive function (complex thinking, applying logic, etc.), attention, and motor coordination appear to be more impaired.

Furthermore, the team found that cognition was impaired to a greater extent with increased dehydration, or a body mass loss of more than 2 percent. Mild dehydration, or a body mass loss of less than 2 percent, did still impair cognitive performance, although not to the same extent.

"There's already a lot of quantitative documentation that if you lose 2 percent in water, it affects physical abilities like muscle endurance or sports tasks and your ability to regulate your body temperature," Millard-Stafford said in a statement. "We wanted to see if that was similar for cognitive function."

Most people may be unable to tell whether they are mildly dehydrated or not, especially because it could happen relatively quickly, perhaps after just half an hour of running, an hour or two of moderate-intensity hiking or even working in a hot environment.

"[Dehydration] could compromise occupational safety, especially in those working in hot factories or outside in summer months," she said. "For those in office settings, dehydration may also impact work proficiency as demonstrated by the deterioration in complex cognitive domains required for integrative thinking—i.e., planning, logic, attentive capacity."

While there are no specific daily requirements for water intake, the National Academies of Science, Engineering, and Medicine suggests that men, on average, should consume around 125 ounces of water per day, while women should take in around 91 ounces.

This will vary from person to person and includes water from all sources, such as food and other drinks. Exposure to heat or strenuous exercise will also increase the amount of water a person needs to drink.

Older people may become dehydrated more easily because they lose their sensation of thirst and their kidneys are less able to concentrate urine, meaning they retain less fluid. Meanwhile, people with high body fat are also at higher risk of dehydration because they tend to have less water reserves than leaner individuals.

Nevertheless, too much water may also be harmful, for example, when people aggrressively drink very large quantities of water in a short time. This can lead to a condition known as hyponatremia, Millard-Stafford said, where the blood becomes diluted and the brain swells. In extreme cases, this can even be deadly.