Hydration, Biological Aging and Long-Term Health

Participants with serum sodium concentrations above 142 mmol/L had a higher risk of developing chronic diseases during follow-up.

At higher sodium concentrations, the relative hazard of developing chronic disease was up to 39% greater compared with the reference group.

The main analysis included heart failure, dementia, chronic lung disease and stroke. Additional analyses also considered diabetes, peripheral vascular disease and atrial fibrillation.

The lowest chronic disease risk was observed at serum sodium concentrations of approximately 138–140 mmol/L.

Importantly, this range represents an observational finding. It should not be interpreted as a therapeutic sodium target.

Participants with serum sodium concentrations above 144 mmol/L had a 21% higher relative hazard of all-cause mortality compared with the reference group.

Hazard ratio: 1.21 (95% CI: 1.02–1.45).

The lowest mortality was observed at serum sodium concentrations of approximately 137–142 mmol/L.

The relationship was not simply linear. Increased mortality was also observed toward the lower end of the sodium range.

This is important because both abnormally high and abnormally low sodium concentrations can reflect disturbances in water and electrolyte balance.

The researchers calculated biological age using the Klemera–Doubal method, which combines multiple age-related clinical biomarkers reflecting different physiological systems.

Participants with serum sodium concentrations above 142 mmol/L were more likely to have an estimated biological age exceeding their chronological age.

At higher sodium concentrations, the adjusted odds were up to approximately 50% greater.

Odds ratio: 1.50 (95% CI: 1.14–1.96).

This does not mean that serum sodium directly measures biological age.

It also does not establish that lower habitual hydration caused accelerated aging. The analysis identified an association between sodium concentration and an estimated biological age derived from clinical biomarkers.

The biological age measure itself was associated with subsequent health outcomes.

Participants whose estimated biological age was higher relative to their chronological age had greater risks of later chronic disease and premature mortality.

The study reported:

* HR 1.70 for chronic disease risk. * HR 1.59 for premature mortality.

This supports the clinical relevance of the biological age measure used in the study.

However, it does not demonstrate that increasing water intake can reduce biological age or improve survival.

Serum sodium reflects the relationship between water and dissolved substances in the blood.

When water availability decreases, sodium concentration can rise even while remaining within the conventional laboratory reference range.

The researchers therefore suggested that serum sodium above approximately 142 mmol/L could help identify individuals who may benefit from further evaluation of hydration and water balance.

But serum sodium is not a direct measurement of daily water intake.

Kidney function, hormonal regulation, medications and medical conditions can all influence serum sodium. A single result therefore cannot determine how much water a person drinks or establish chronic dehydration.