Researchers say that as people age, they need to drink more water to compensate for changes in their body temperature regulation.
They say dehydration can cause a number of ailments, including muscle pain, fatigue, and heat exhaustion.
They urge older adults to drink water even when they aren’t thirsty and to limit beverages such as soda, coffee, and alcohol, which can cause dehydration.

As you get older, you need to drink more water.

That’s the advice from a new study published in The Journal of Physiology.

The researchers from the University of Ottawa point out that hydration is key in regulating body temperature and helping fight off a host of other health problems.

The researchers said that dehydration doesn’t reduce heat loss or increase body temperature in older adults during exercise as it does in younger people, which may seem on the surface like a beneficial response.

But that means that when older people exercise, their bodies don’t adjust the rate of sweat loss to prevent further dehydration.

This results in greater strain on the heart, evidenced by a more pronounced increase in heart rate compared to younger men.

The study featured older men, although the results pointed to all older adults as those affected.

The researchers added that “until recently, however, our understanding of the effects of dehydration on body temperature regulation came primarily from studies conducted on young adults.”

“This is an interesting study, as it delivers new insights into fundamental age-related changes to our physiology,” Dr. Scott A. Kaiser, a geriatrician at Providence Saint John’s Health Center in Santa Monica, California, told Healthline.

“While changes in the regulation of body heat, sweating, hydration, and thirst that tend to occur with age are well established, this study probes deeply into the specific changes of underlying mechanisms. In particular, changes in response to dehydration and heat with exercise,” he explained.

“It’s quite remarkable that, at this point in time, we are still learning such fundamental things about the way our bodies change with age,” Kaiser added.

“That said, given our aging population — with a 30-year gain in life expectancy over the last century, [with] roughly 10,000 baby boomers turning 65 each day, and declining birth rates — we are approaching the first time in human history in which our population will have more people over the age of 65 than under the age of 18. We need to continue to increase our understanding of the fundamental physiology of aging.”

Researchers said that a reduced sensitivity in older people to elevated blood osmolality (concentration of salt) could explain the blunted effect of dehydration on hearing loss and body temperature regulation in older adults during exercise and in greater heat.
Why body temperature matters

The researchers found that in contrast to young adults, the regulation of body temperature in the older subjects wasn’t influenced by the increase of saltiness in the blood.

Less efficient regulation of body temperature contributes to an increased risk of heat exhaustion, heat stroke, adverse heart problems.

“When it comes to the elderly, there are a couple things we need to remember,” Dr. Nodar Janas, medical director of Upper East Side Rehabilitation and Nursing Center in New York, told Healthline. “As we get older, our thirst center — which is located in the hypothalamus — isn’t as active as it used to be, so the brain doesn’t always give the signal that we need to drink. We need to make an extra effort to ensure that the elderly consume appropriate amounts of fluids, whether they’re thirsty or not.”

He continued, “If an elderly person gets dehydrated, one of the first organs to suffer are the kidneys, which can cause acute kidney failure. Dehydration also creates electrolyte imbalances, which can be deadly.

“Another anecdotal point to mention is that the elderly seem to have a worse tolerance to cold,” said Janas. “As we age, we prefer warmer temperatures and sometimes too warm of an environment can lead to excessive perspiration without realizing you’re dehydrated.”

Being aware of aging

Dr. Rand McClain, founder of Regenerative & Sports Medicine in Santa Monica, California, told Healthline that he sees one particular problem among older people, especially men, when it comes to dehydration: They’re not aware or accepting of how their body changes with age.

“They are less likely to be wary and more likely to ignore signs of dehydration and heat-related illness because they have a past history that is unrepresentative of their new status as older adult males,” McClain said.

He added that older men might think, I have been doing it like this my whole life without a problem, so why should I change now?

“Most people have never experienced the severe symptoms associated with dehydration and, if dehydrated, are usually mildly so and able to compensate without much effort,” McClain said.

“We have air-conditioned environments, water fountains, and fluids so easily accessed in most places. However, many people do indeed live in a mildly dehydrated state because of the diuretic beverages they consume, such as coffee, tea, and caffeinated soft drinks and alcohol.”

McClain said we tend to “dry out” as we age, as our water composition can change from roughly 70 percent to as little as 50 percent.

“We need water for everything to operate smoothly and at its best,” he said. “While we can go for weeks or months without food, we can go without water for only days. Even being slightly dehydrated to 98 percent of normal can affect one’s metabolism negatively and reduce athletic and organ performance.”
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How to hydrate

Dr. Nicole Avena, an assistant professor of neuroscience at Mount Sinai School of Medicine in New York, told Healthline that dehydration can cause other problems, such as fatigue and muscle weakness.

She said a 2015 studyTrusted Source found 37 percent of people 65 and older admitted to emergency rooms showed signs of dehydration.

When it comes to how to hydrate, she says sticking to water is best.

“When you drink things like sodas and beverages that contain ingredients other than water, your body needs to work to process those ingredients,” Avena said. “Plain water is the best hydrator because your body can benefit from it without having to simultaneously process sugars, additives, and other ingredients that don’t have any benefit to health.”

Kristin Gillespie, MS, CNSC, a registered dietician with the website Exercise with Style, told Healthline that the abundance of nutrients hyped for health benefits tend to muddy the waters, so to speak, when it comes to how to hydrate.

“This makes it hard for the public to decide what nutrients are more or less important than others,” Gillespie said. “Water consumption and hydration is hard for a lot of people to appreciate because water offers no nutritional value.”

She said that besides thirst, other symptoms of dehydration include dark or infrequent urination, dry skin and lips, muscle cramps (especially in legs, feet, and hands), low blood pressure, elevated heart rate, fatigue, and “general malaise.”

And staying hydrated can also help avoid illnesses.

“An added benefit of drinking lots of water is its positive effect on immunity,” Gillespie said. “Consuming adequate fluids helps keep you healthy by helping your body naturally rid itself of bacteria and other toxins.”