It's perfectly normal to feel ugly after the night rolls over and turns or stays up. But new research shows that there may be more than just sleep deprivation to blame: You might also be dehydrated, say the researchers, and drinking more water can help you feel better.
Studies published this week in the journal Sleep, found that people who reported sleeping regularly for only six hours a night were 16 to 59% more likely to "not be adequately hydrated" (based on their urine sample analysis) than those who said they usually slept eight. Both Americans and Chinese adults participated in the study – around 25,000 people – and the results were consistent in both populations.
That does not mean that people who lack sleep also drink less; in fact, the study authors actually controlled total fluid consumption among several participants. They found that even when people reported drinking the same amount, those who slept less were more likely to have more concentrated urine and other signs of dehydration.
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So what happened? The study author said it might have something to do with a hormone called vasopressin, which helps regulate the body's hydration status.
Vasopressin is released both day and night, but production actually rises later in the sleep cycle, said lead author Asher Rosinger, assistant professor of biobehavioral health and anthropology at Penn State University, in a press release. "So, if you wake up early, you might lose a window where more hormones are released, causing a disruption in the body's hydration," he added.
The authors point out that poor sleep has been linked in previous studies with chronic kidney disease, and they say that dehydration might be a significant driver of that relationship. Long-term dehydration can also increase a person's risk of kidney stones and urinary tract infections.
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Because this study relies on self-reported sleep data and only sees urine output at one point in time, it can only find a connection between the two – not a causal relationship. Future research should look at this relationship for one week, the authors wrote in their paper, to understand how people's hydration and sleep status changes every day.
The National Sleep Foundation states that adults must sleep seven to nine hours a night and should keep your sleep and wake time as consistent as possible. (In this study, sleeping more than nine hours a night did not seem to have any effect, in either direction, on hydration status.)
Of course, you really don't need to other the reasons for reducing sleep are not good for you: This is also associated with a higher risk of cardiovascular disease, overeating, weight gain (although not related to overeating), and diabetes, to name a few. This can also cause short-term problems, such as irritability, difficulty concentrating, memory problems, and driving drowsiness.
But dehydration itself has also been shown to cause headaches and fatigue and to influence mood, cognition, and physical performance – which might add to the already negative effects of sleepless nights, the authors said. "This study shows that if you don't get enough sleep, and you feel bad or tired the next day, drink extra water," Rosinger said.
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