A study by researchers at the National Institutes of Health (NIH) shows that people who don't drink enough water are at greater risk for chronic disease and more likely to die prematurely. The study, published in 2023, was inspired by previous work by the same group of scientists at the National Institutes of Health studying the health effects of long-term water restriction in mice. That 2019 study found that chronically depriving mice of adequate water shortened their lifespan by about six months — the equivalent of 15 years in humans.
So this follow-up study set out to explore whether optimal hydration levels in humans impact health and aging. To do this, the team looked at data from a long-term heart health study that began in the late 1980s. The data includes more than 15,000 participants and was followed for an average of more than 25 years.
The researchers studied serum sodium levels in blood samples as a surrogate measure of water content. In healthy people, which has long been considered a valid measure of body hydration, normal serum sodium levels are between 135 and 146 mmol/L. Prolonged dehydration can lead to elevated serum sodium levels.
Serum sodium levels in the cohort were measured at multiple time periods over 25 years, and 15 health markers used to assess biological aging were also tracked. These include blood pressure, immune biomarkers and blood sugar levels.
Overall, the study found a significant correlation between participants with serum sodium levels above 142 mmol/L and increased rates of biological aging. More specifically, participants with serum sodium levels above 142 mmol/L were up to 15% more likely to be biologically older than their chronological age. That jumped to 50% among people with serum sodium levels above 144 mmol/L.
In terms of chronic diseases, people with serum sodium levels above 142 mmol/L had a 64% increased risk of developing chronic diseases, including heart failure, diabetes and dementia. People with the highest serum sodium levels (144.5-146 mmol/L) were 21% more likely to die prematurely compared with those with the lowest serum sodium levels.
Of course, it’s important to note that correlation does not necessarily imply causation. The researchers caution that these findings do not directly indicate that long-term reduced hydration leads to shortened lifespan. It's possible that low daily hydration levels are simply a proxy for a healthy lifestyle, and that people who stay well hydrated also happen to eat better and exercise more.
But the researchers did note that there is some laboratory evidence that low levels of hydration trigger signs of aging in animal and human cells. These studies suggest that increased serum sodium leads to pro-inflammatory activity and DNA damage associated with accelerated aging. Therefore, it can at least be hypothesized that chronic underhydration can lead to age-related diseases.
A recent review article published in 2024 found that "an increasing number of epidemiological studies have linked markers of water deprivation (such as elevated plasma vasopressin, sodium levels at the upper end of the normal range, low urine output, and high urine osmolarity) with an increased risk of adverse health outcomes, such as the future development of chronic disease and premature death."
People with serum sodium levels above 142 mmol/L may benefit from increased fluid intake, said Natalia Dmitrieva, co-author of the 2023 NIH study. It is estimated that about 50% of people do not meet the recommended daily fluid intake. Therefore, Dmitrieva believes that if further research can verify the link between hydration and overall health, this simple intervention could have a significant impact on global health.
"Globally, this could have a big impact," Dmitrieva explained. "Reduced water content in the body is the most common factor leading to increased serum sodium, which is why research results show that staying well hydrated can slow down the aging process and prevent or delay chronic diseases."
The new research is published in the journal eBioMedicine.