Could levels of hydration affect cognitive function?

by Bhushan

Posted on March 17, 2020 at 12:00 PM

Dehydration can cause headaches and other physiological complications and older adults are at greater risk of developing it. But, does it affect executive ability too? And could overhydration impair mental output, too?

Dehydration may cause headaches, lethargy, dizziness and many other issues based on how serious it is. Studies have continued to concentrate on the impact of dehydration in younger populations — especially in sports and exercise, where over-exertion and sweating may cause people to lose more water than they consume.

One population group, though, is especially vulnerable to dehydration: the older adults.

"When we mature, our water supplies are decreasing due to body mass declines, our kidneys are becoming less effective at storing water, and hormonal signals that cause hunger and encourage water consumption are blunted," notes Hilary Bethancourt, Ph.D., of the Pennsylvania State University College of Health and Human Development at State College.

Older people have an elevated chance of neurological disability, too. Do their levels of hydration and cognitive capacity in some way relate? Bethancourt and colleagues have set out in a recent analysis to address the question. Our studies are now published in the European Nutrition Review.

Both under and overhydration are non-ideal

The researchers, in their study, analyzed data from 2,506 participants— 1,271 women and 1,235 men— aged 60 and over. Such data were gathered in 2011–2014 through the Diet and Health Review Study.

Many of the research participants were able to send blood samples. They also received detail about what they had eaten during the day preceding the collection of blood samples

The investigators looked at the concentration of various substances and compounds — including sodium, potassium, glucose, and urea nitrogen — in their blood to determine the hydration levels of each patient.

Both participants have carried out cognitive performance assessments, including tasks intended to measure speech retention and fluency, and concentrated experiments on levels of concentration and working memory.

At first glance, the researchers find a correlation in the executive function assessments between sufficient hydration and positive performance. Nevertheless, as the researchers tailored their study of mitigating variables, the conclusions were less apparent.

"When we adjusted for age, employment, hours of sleep, amount of physical activity, and diabetes status and evaluated the results separately for men and women, correlations with hydration status and water consumption decreased," Bethancourt says.

Just some of the connections remained of interest after these redeployments. The study in particular found that women tended to show lower executive efficiency when underhydrated. The same applied in overhydrated conditions.

"The most popular result left after we adjusted for other important variables was a regression towards lower scores on [one of the cognitive function tests] for women who were classified as either underhydrated or overhydrated," states Bethancourt.

"The test of concentration, processing speed, and working memory," she says, was the task where those who were overhydrated or underhydrated worked out the most of liquids.

"It was important that while [this test] lasted just a few minutes, it was the one most closely associated with lower rates of hydration," Bethancourt says.

"Similarly, other work has shown that concentration may be one of the cognitive realms most influenced by hydration. This left us wondering what the impact of insufficient hydration may have on more complex activities that require longer attention and concentrate cycles, "she adds.

However, the researchers were unable to determine that non-ideal levels of hydration induced poorer cognitive output, or whether people who may have already had cognitive impairments were also more likely to consume too little or too many liquids

For older people, too, the lack of a correlation between hydration levels and cognitive function remains a mystery.

While several questions need to be resolved, Prof. Asher Rosinger, co-author of the report, recommends older adults should not endanger their safety by ignoring proper hydrating.

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