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Hydration, Heart Health, and Aging Well

By Heather Davis, MS, RDN, LDN

Hiding in plain sight, the importance of hydration is often underestimated. For some, reaching for an expensive supplement claiming to enhance cardiovascular health and blunt cellular aging may seem like a more compelling option—with or without supporting evidence—than simply increasing daily water intake. But what if one of the most effective ways to support cardiometabolic health through the lifespan was also one of the most accessible? With the help of new research, it’s time to get back to basics and appreciate all that hydration brings to the table.

The human body is composed of roughly 60% water—a vital component for biochemical reactions, cellular structure, and physiological function. While short-term consequences of dehydration like fatigue, headaches, dizziness, and impaired cognition are well known, researchers have begun to illuminate potential long-term impacts of hydration status on aging, chronic disease, and mortality. Crucially, the concentration of sodium in the blood—often indicative of hydration levels—appears to correlate with biological aging and the risk of developing chronic illnesses.1

The Science Behind Hydration and Aging
Water is essential for maintaining blood volume, regulating body temperature, driving nutrient transport, and facilitating waste elimination, among many other functions. Beyond these immediate roles, hydration at both the cellular and systemic level may affect aging processes. Hydration is commonly assessed using serum sodium concentration, a measure of sodium in the blood that rises when fluid intake is insufficient and body water content drops.

A pivotal study published in eBioMedicine examined how serum sodium levels within the normal range (135 to 146 mEq/L) relate to aging and long-term health outcomes in humans. This work builds on decades of data from the Atherosclerosis Risk in Communities (ARIC) study, a long-term observational research project involving thousands of individuals followed over 25 to 30 years.

Key Findings From the National Institutes of Health/ARIC Analysis
Researchers focused on over 11,000 adults who were first assessed in midlife and followed into older age. They evaluated the following:

• biological aging was determined using 15 biomarkers characterizing performance of multiple organ systems and processes: cardiovascular (systolic blood pressure), renal (eGFR, cystatin-C, urea nitrogen, creatinine, uric acid), respiratory (FEV), metabolic (glucose, cholesterol, HbA1c, glycated albumin, fructosamine), and immune/inflammatory (CRP, albumin, beta 2-microglobulin);
• chronic disease incidence, including conditions like heart failure, stroke, dementia, diabetes, and chronic lung disease; and
• all-cause mortality, or overall risk of premature death.

The results revealed that adults with serum sodium levels above 142 mEq/L were more likely to exhibit accelerated biological aging, meaning their biological metrics suggested they were older than their chronological age. Those with levels above this threshold also faced a markedly higher risk—around 40% higher—of developing chronic diseases, such as heart conditions, lung disease, diabetes, and dementia, in later life. Serum sodium levels in the upper normal range (144.5 to 146 mEq/L) correlated with a 20% increased risk of premature death compared to people with mid-range sodium levels.

In contrast, adults whose sodium levels stayed between approximately 138 to 140 mEq/L—suggestive of better hydration—tended to show the lowest risk for chronic disease and premature mortality.

These trends appear even after adjusting for confounding factors such as age, sex, race, smoking status, and health conditions like hypertension, suggesting that hydration status itself may play an independent role in long-term health.1

Dehydration: A Driver of Aging and Disease?
While the ARIC study was observational and cannot prove definitive cause and effect, its findings align with growing evidence that inadequate hydration may accelerate aging and increase susceptibility to chronic conditions.

Why might hydration influence aging and disease? Several physiological pathways offer clues.1

• Cellular function and repair: Water is essential for enzymatic reactions, protein synthesis, and DNA repair—processes that are critical for maintaining tissue health and preventing age-related decline.
• Inflammation and oxidative stress: Dehydration can lead to subtle increases in inflammatory markers and oxidative stress, both of which are implicated in chronic disease and aging.
• Cardiovascular strain: Low fluid levels increase blood viscosity and strain the heart and vessels, potentially accelerating cardiovascular aging.
• Metabolic efficiency: Adequate hydration supports regulation of glucose and lipid profiles; dehydration may disrupt these balances.

How Much Water Is Enough?
Despite clear associations between hydration and health outcomes, researchers caution that serum sodium is only a proxy for hydration and not a definitive measure of fluid intake.

Nonetheless, practical guidance can help individuals maintain proper hydration over a lifetime. Health authorities such as the National Academies of Medicine recommend daily fluid intake targets that can serve as general goals:

• Women: Approximately 2.7 liters daily.
• Men: Approximately 3.7 liters daily.

These totals include fluids obtained from beverages (eg, water, tea, juice) and high-water foods like fruits and vegetables.

It’s important to note that individual needs vary based on factors such as climate, physical activity, age, and health conditions. Older adults may have a reduced sense of thirst and thus may inadvertently underestimate hydration needs. People with specific medical conditions—like kidney or heart disease—might have fluid recommendations further tailored by health care providers.

Because thirst is not always a reliable indicator, particularly in older adults, other simple measures like assessing urine color can help gauge hydration. Pale, straw-colored urine generally suggests adequate hydration, while dark yellow may indicate dehydration.

Final Thoughts
Researchers note that a significant percentage of adults worldwide do not meet recommended fluid intake levels. Given an aging global population and rising rates of chronic diseases such as diabetes, CVD, and dementia, strategies that even moderately reduce risk could have substantial impact on public health outcomes.

Access to safe, affordable drinking water remains a challenge in some communities. Addressing disparities in water access and promoting hydration education are valuable components of broader efforts to reduce chronic disease burden and promote healthy aging.

— Heather Davis, MS, RDN, LDN, is editor of Today’s Geriatric Medicine.

Reference
1. Dmitrieva NI, Gagarin A, Liu D, Wu CO, Boehm M. Middle-age high normal serum sodium as a risk factor for accelerated biological aging, chronic diseases, and premature mortality. eBioMedicine. 2023;87:104404.