The following is a guest article by LMNT community member Dr. Peter Attia, a Stanford/Johns Hopkins/NIH-trained physician focusing on the applied science of longevity, the extension of human life, and well-being. His new book, Outlive: The Science & Art of Longevity, is available now.
For most of my life, I never gave much thought to hydration. I would drink when thirsty, and as far as health and longevity were concerned, that seemed like it would always be enough. I was painfully wrong: Blunted thirst responses, as are common for older folks, can result in dehydration. Dehydration impairs balance and can raise the risk of falls, a leading cause of death for seniors. Hydrating for longevity, therefore, means adopting strategies as we age that boost fluid intake, absorption, and retention.
About a year and a half ago, the truth about blunted thirst responses literally hit me in the face. A few days after donating three units of blood and flying the next day for 12 hours, with no awareness that my thirst mechanisms had been impaired due to these unique circumstances, I stood up too quickly, briefly passed out, and fell into a table. Had I been 20 years older, more frail, or even just in a more treacherous environment than my hotel room, such a fall could have resulted in serious injury or even spelled the end for me, but I was lucky – the only consequences were some forehead stitches, a couple of small scars, and an important lesson: take hydration seriously. When I returned home from my trip, I made it my mission to better understand how to hydrate properly, and how my hydration strategy may need to evolve over time.
The damage caused by falls
Despite being a common feature in slapstick comedy, falls are no laughing matter, especially as we advance in years. Falls are the seventh leading cause of death among adults over age 65, with a quarter of older adults in the United States reporting a fall each year. The Center for Disease Control (CDC) estimates that accidental falls were directly responsible for over 42,000 deaths in 2020, and the numbers have been steadily increasing for more than a decade.
Even when falls are not directly fatal, they can often result in debilitating injuries which drastically reduce quality of life and cause more rapid deterioration of health than would occur otherwise. For instance, falls account for 95% of hip fractures, which are associated with high mortality rates within one year after injury in older adults. Falls are also the leading cause of traumatic brain injuries and related deaths.
In all, approximately one in five nonfatal falls results in serious injury, and nearly 7 million emergency room visits across ages each year in the U.S. involve nonfatal fall-related injuries – nearly two out of every hundred individuals.
How does dehydration increase fall risk?
Blood is mostly made up of water, so when we become dehydrated, blood volume decreases. The resulting drop in blood pressure makes it harder for blood to supply sufficient oxygen and nutrients throughout the body, especially to elevated areas such as the brain. For this reason, even mild dehydration can cause lightheadedness and dizziness, increasing the risk of losing balance. According to one 2020 study, older adults who are dehydrated are at 13% higher risk of falls than their euhydrated (optimally hydrated) counterparts, as determined in a three-year follow up period.
The risk is particularly high for individuals who experience postural orthostatic hypotension (POTS) – an exaggerated drop in blood pressure when transitioning from sitting or lying down to standing upright. Orthostasis is its own risk factor for falls, and when these effects are compounded with those of dehydration, they can, as in my case, easily be enough to cause a momentary loss of consciousness upon rising, resulting in collapse.
Dehydration is common in older adults
For many of us, “dehydration” conjures images of running marathons or wasting away in a desert with an empty canteen, but dehydration can be much more subtle and, particularly in older adults, is alarmingly common. In the 2020 study cited above, a staggering 38% of the >30,000 patients were found to be at least mildly dehydrated, while others report that dehydration prevalence among the elderly may be as high as 60%.
Why are older adults at such high risk of dehydration? While there are multiple underlying causes, one critical factor is that, as we age, our thirst responses gradually become blunted, so we are less aware of our dehydration and therefore tend not to consume enough water to replace losses. So not only are elderly adults at greatest risk of serious injury or death from falls, they are also at greater risk for dehydration contributing to those falls. Together, these facts underscore the necessity for devoting increasing attention to hydration as we age.
Strategies to prevent dehydration
Fortunately, as far as health risks are concerned, the prevention strategy for dehydration is remarkably simple and effective. If you’re young and have not recently lost fluid unusually quickly (such as from donating blood or exercising in high heat), drink to thirst. For older folks, or if you find yourself in unique or medical circumstances that may blunt your thirst mechanism, make a conscious effort to drink more fluids. Many fitness and diet apps provide functionality for logging water intake and setting reminders, which can be helpful for ensuring adequate intake despite situations that could result in blunted thirst. For seniors, making fluids more palatable is another way to encourage greater intake, as numerous studies have shown that the addition of pleasant, non-caloric flavoring to water raises voluntary intake.
An important component of everyone’s hydration strategy should be to consume fluids with sodium and other electrolytes. Electrolytes boost absorption of fluids in the gastrointestinal tract when present at concentrations up to about 200 mg/fl oz, so for the same fluid volume, an electrolyte solution is more hydrating than pure water.
Sodium is the most important, in part because it can be consumed safely in the quantities that render water “isotonic,” meaning at a concentration that restores the critical balance of sodium in the body. Further, sodium is essential for making use of the fluid we consume and absorb. The body’s sodium level is the major determinant of how much of our body water is distributed into the blood and other tissues versus excreted, so consuming fluids with sodium can help ensure that we are getting the most out of the water we consume.
Hydrate for longevity
As we get older or when we lose fluid too quickly, we cannot rely on thirst alone to tell us that our bodies need water, so adopting strategies to boost fluid intake, absorption, and retention in these circumstances deserve special attention. If there is one silver lining in my face-to-face (or face-to-table) encounter with this fact, it is that I walked away with a new awareness of the importance of hydration for longevity before it was too late – and I hope that in sharing this lesson, I have spared some of you from learning in the same painful way that I did.
