Everyone knows staying hydrated is important, but new research highlights just how important it is for a less obviously related area of health – sleep.
In the hypohydrated state, participants slept about an hour longer than their baselines on average, but, they reported having a significantly harder time falling asleep and feeling more fatigued the next morning.
This work was led by Elaine Choung-Hee Lee, professor of kinesiology in the College of Agriculture, Health and Natural Resources (CAHNR), and Lawrence Armstrong, professor emeritus, alongside Alan Ky, a Ph.D. student in Lee’s lab, and in collaboration with Yasuki Sekiguchi, assistant professor of kinesiology at Texas Tech University and a former Ph.D. student and postdoctoral fellow in Lee’s lab. Their findings were published in SN Comprehensive Clinical Medicine.
“Everyone says to drink water, but they don’t know why,” Ky says. “I think we’re providing really good context for what you should be doing and how it is affecting your health. And this is just the start.”
The study had 18 college-aged males report to the lab for four consecutive days. On the first day, they established a baseline hydration status. On the second day they were euhydrated, meaning they were well-hydrated from having consumed 500 milliliters of water the evening prior. Participants were instructed to not drink anything after the lab visit on day two so that they arrived at the lab in a hypohydrated state on day three. Following that, they were told to drink and eat as they normally would, and the final measurements were taken on the fourth morning.
The researchers tested participants’ urine specific gravity (the amount of solutes in urine – a lower solute concentration indicates better hydration), urine color, and body mass loss which are all indicators of hydration status.
Participants completed a survey about the length and quality of their sleep each night, answering questions about things like how long it took them to fall asleep, if they woke up throughout the night, and if they dreamed.
By giving participants such specific instructions and controls, the researchers were able to establish a confident connection between hydration and sleep.
“We used multiple well-accepted hydration markers,” Lee says. “We started them off in the study knowing they were euhydrated and started in that controlled state and additionally gave them instructions to only manipulate fluid consumption patterns. So, we know that between when you come to the lab and your next visit, we know that the big difference is how much fluid you’ve consumed.”
While this study was initially conceived of in the context of athletic performance, which can be impacted by poor sleep and fatigue, the dehydration levels imposed on study participants are not uncommon.
“These are levels of dehydration that we’re seeing people walk around with,” Lee says. “You may not know why all morning you feel a little fatigued, or you’re having trouble sleeping at night, and some of it may have to do with your daily, habitual fluid consumption habits.”
As part of this study, the researchers also collected blood samples which they are using to write a forthcoming paper about how dehydration impacts immune cell function. They are also interested in studying these factors in pregnant women and children who may be more vulnerable to the adverse effects of dehydration.
“This study and the design of it has built a foundation for a whole line of research to investigate multiple aspects of sleep,” Lee says. “We’re looking at performance during exercise, cardiovascular response over time, the effect on cells and immune response. So many aspects we know from other studies are related to sleep, but we’re able to do it in a really controlled way.”
This work relates to CAHNR’s Strategic Vision area focused on Enhancing Health and Promoting Diversity, Equity, Inclusion and Justice.
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