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1-24-23

Link between hydration, aging studied

• Higher blood sodium in middle age was associated with increased mortality, chronic disease risk, and biological aging.
• The findings suggest that poor hydration may accelerate biological aging and increase the risk of chronic disease and death.

As people live longer, the world's population is aging. This has led to an epidemic of age-related chronic diseases. Finding ways to slow down aging and prevent such diseases has become a pressing task for medical research.

Studies in mice have shown that restricting water intake shortens the mouse lifespan and leads to organ degeneration. This suggests that staying properly hydrated might help slow down the aging process. A research team at NIH's National Heart, Lung, and Blood Institute (NHLBI), led by Dr. Natalia Dmitrieva, explored whether hydration might also be associated with aging in people. Their findings appeared in eBioMedicine on Jan. 2.

The team looked for associations between aging and hydration in data from a study that followed more than 15,000 people from four U.S. communities for more than 25 years. Participants were 45-66 years old at the beginning of the study. As part of the study, sodium levels in the participants' blood sera were measured at enrollment and at their first follow-up visit three years later. Serum sodium goes up as people drink less fluids, so serum sodium levels can serve as a proxy for hydration.

The team looked at study participants with normal levels of serum sodium-between 135 and 146 mmol/L. They found that, even within this range, differences in serum sodium were associated with differences in mortality. People with serum sodium near the middle of the normal range-137 mmol/L to 142 mmol/L-had the lowest mortality rate. Those with serum sodium above 144 mmol/L had 21% greater risk of dying at an earlier age. Higher serum sodium was also associated with increased risk of chronic diseases including heart failure, dementia, chronic lung disease, and stroke.

The researchers calculated the participants' biological age based on various biomarkers. The risks of premature mortality and chronic disease both increased with biological age. And people with serum sodium levels above 144 mmol/L were 50% more likely to have a biological age greater than their chronological age.

The results suggest that serum sodium above a certain threshold may be a risk factor for faster aging. This, in turn, increases the risk for chronic disease and premature death.

Reduced fluid intake is the most common reason for elevated serum sodium. Thus, Dmitrieva says, "proper hydration may slow down aging and prolong a disease-free life."

The researchers note that their results don't prove that elevated sodium causes accelerated aging. Establishing a causal link will require randomized controlled clinical trials. But the findings do suggest that a clinical evaluation could help people with elevated serum sodium. They may benefit from drinking more fluids, or may have underlying conditions that lead to fluid loss.

For further information on this and other health topics, visit the web site of the National Institute of Health at www.nih.gov.