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As anyone walking around with a 40-ounce Stanley tumbler will tell you, hydration is important. New research shows it might even impact sleep.
In a study published earlier this year in the journal SN Comprehensive Clinical Medicine, researchers found that participants in a hypohydrated, or dehydrated, state slept more but had greater trouble falling asleep. Understanding sleep dynamics carries significant implications for a world where sacrificing health and sleep for work has become completely normalized.
“Sleep influences health and is affected by dehydration. Therefore, our aim was to assess the effects of mild dehydration and subsequent rehydration on sleep time and sleep quality using subjective measures,” the team wrote in the paper.
The team asked 18 college-aged males to come to the lab for four days in a row and follow a particular hydration pattern. On day one, the researchers identified their baseline hydration status and asked them to drink a little over two cups of water (500 milliliters) that evening. That meant that on day two, they were euhydrated, or well-hydrated. After visiting the lab that day, the team asked the men not to drink anything.
As such, they returned on day three in a hypohydrated state. They were then instructed to drink and eat normally until the final visit on day four. During this time the team investigated their hydration status by testing the amount of solutes in their urine (a lower concentration means better hydration), urine color, and body mass loss.
“We used multiple well-accepted hydration markers,” Elaine Choung-Hee Lee, study co-lead and a kinesiologist at the University of Connecticut, said in a university statement. “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.”
The participants reported the length and quality of their sleep each night, including things such as if they woke up during the night, if they dreamed, and how long it took them to fall asleep. This approach revealed an association between hydration and sleep. In a dehydrated state, the participants reported sleeping around an hour more on average than their baselines but also had more trouble falling asleep than when they were drinking normally. Interestingly, though, participants were more fatigued before sleep while dehydrated than when they were well-hydrated.
“During each hydration state, the subjects did not experience any statistically significant differences in sleep quality, number of dreams, or number of awakenings,” the researchers summarized in the paper. “Therefore, the main findings of this study are that sleep time significantly increased during mild dehydration (DEH) than on all other days (baseline, EUH [euhydrated], AD [normal hydration]), subjects reported falling asleep easier on AD compared to DEH, and evening fatigue was greater in DEH than in EUH.”
While such a controlled environment might feel far from normal life, Lee explained that people experience these same levels of dehydration outside of the context of a study. “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,” she explained in the statement. Moving forward, the team will analyze blood samples collected during this trial to investigate how dehydration impacts immune cell function.
Now you have another reason to buy that cute “stay hydrated” sticker for your laptop.
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