How Dietary Habits and Nutritional Deficiencies Relate to Hyponatremia in Older Adults

1. Introduction

Hyponatremia is defined as a serum sodium level below 135 mEq/L and is a common occurrence in older adults.[1] Globally, an estimated 703 million people are age 65 and older. This number is expected to double by 2050, which may further strain healthcare systems.[2] The prevalence of hyponatremia is around 8% in the general population but rises sharply in older adults, particularly in hospital settings, where it can range from 15% to 30%.[3] In community-dwelling older individuals aged 75 and above, the prevalence reaches approximately 11.6%.[4] Hyponatremia is more frequently observed in patients in acute-care hospital, critical care units, ambulatory-care settings, and geriatric populations than in the general population.[1,5,6] The prevalence of hyponatremia increases with age.[7] Its prevalence is about 18% in older adults compared to 2.98% in younger groups. Strategies for hospitalized older adults should include plans that optimize sodium balance and prevent adverse outcomes associated with hyponatremia, such as cognitive impairment, falls, and increased morbidity.[8]

This condition is of great clinical concern as it increases the risk of morbidity and mortality, cognitive decline, falls, and fractures, which significantly impair quality of life and increase healthcare costs by up to 20%.[9] This review aims to explore the relationship between dietary habits, nutritional deficiencies, and hyponatremia in older adults, summarizing the implications for clinical practice and prevention.

Sodium is critical in maintaining cellular homeostasis, fluid balance, nerve function, and circulatory pressures. The bioavailability of sodium is reduced as individuals get older. Physiological changes, such as decreased glomerular filtration rate (GFR), impaired sodium conservation, and reduced sodium bioavailability contribute to this reduction.[10] Older adults are vulnerable to hyponatremia due to factors such as malnutrition, chronic diseases, and polypharmacy. The presence of impaired dietary intake, especially if low in sodium and protein consumption increases the risk of hyponatremia. This is evident in conditions such as “tea and toast” syndrome. The syndrome results from an insufficient intake of key nutrients, that result in sodium depletion due to a fluid imbalance.[1]

The clinical consequences of hyponatremia in older adults are significant. Hyponatremia impacts cognitive function and may result in delirium. In the hospital setting this could result in increased length of hospital stay increasing the risk of institutionalization, functional dependence, and mortality. [11] Therefore, understanding the role of dietary habits and nutritional deficiencies in developing hyponatremia is needed to develop effective prevention and management strategies tailored to this vulnerable population.

2. Methods

This narrative review was conducted to explore the relationship between dietary habits, nutritional deficiencies, and the incidence of hyponatremia in older adults. The aim was to provide a comprehensive understanding of the topic of diverse sources available in MedSurg literature, focusing on clinically relevant insights. A comprehensive literature search was conducted using PubMed, focusing on articles published in peer-reviewed journals. Key words included “hyponatremia,” “older adults,” “dietary sodium,” “nutritional deficiency,” “sarcopenia,” and “fluid balance.” Additional searches were performed using terms related to “frailty” and “malnutrition” to ensure the inclusion of studies addressing broad aspects of hyponatremia in the older populations. Our approach focused on summarizing findings from clinically significant studies to offer a broad perspective on how dietary and nutritional factors may impact hyponatremia. Articles were chosen based on their relevance, the insights they offered into the interaction between nutrition, sodium balance, and the hyponatremia risks in older adults.

• Understanding Hyponatremia in Older Adults

• Overview of Sodium Balance and Regulation in the Body
  Serum sodium is vital for maintaining fluid balance, regulating nerve and muscle cell function, and facilitating the transport of substrate across membranes.[7] Its critical roles influence hyponatremia's acute and chronic manifestations. A rapid decrease in serum sodium within 48 hours can lead to symptoms such as headaches, nausea, vomiting, and potentially progress to seizures and coma.[1] Chronic hyponatremia can manifest as fatigue, cognitive impairment, and gait deficits, leading to falls, osteoporotic fractures, and many associated symptoms.[12,13,14,15,16]
• Factors Contributing to Hyponatremia in the older adult
  Age is an independent risk factor for hyponatremia in older adults, often due to medications, endocrinopathies, syndrome of inappropriate antidiuretic hormone secretion (SIADH), and malnutrition, and at times leading to the development of 'tea and toast' syndrome.[1] Some common causes of hyponatremia are given in Table 1.
  
• “Tea and Toast” Hyponatremia
  One notable example of a dietary habit leading to malnutrition and hyponatremia in older adults is the “tea and toast” syndrome. Tea and toast are typically deficient in sodium, protein, and other vital nutrients. Older individuals whose primary diet consists of such a diet increase their risk of developing hyponatremia. [17] Such a dietary pattern is often seen in older adults with poor appetite, difficulty preparing meals, or limited access to diverse food sources. A “tea and toast” diet results in sodium depletion. This in combination with excessive water intake, results in dilution of sodium levels in the blood, creating fluid imbalance, causing hyponatremia. Additionally, protein deficiency in such diets exacerbates malnutrition, contributing further to sarcopenia and frailty.[18,19]
• Hyponatremia and Falls
  Hyponatremia that is symptomatic is readily diagnosed and managed. Mild chronic hyponatremia presents a more significant challenge because of its links to adverse outcomes. Hyponatremia increases the risks of falls by contributing to neurocognitive impairment, which can cause gait instability and decreased attention span.[20] This has substantial implications for geriatric care, as falls are a common medical concern among older adults.[21] Falls affect 30-60% of older adults living independently in the community yearly.[22] The outcomes of such falls in older adults can include hip fractures, hospitalizations, head injuries, and the need for admission to long-term care facilities.[21] Furthermore, prospective data from the Rotterdam Study demonstrated a significant association between baseline mild hyponatremia and recent falls, as well as both vertebral and incidental non-vertebral fractures.[12] Epidemiological and experimental evidence has shown that chronic mild hyponatremia is an independent risk factor for osteoporosis, as it increases bone osteoclastic activity in a hyponatremic environment.[23] Chronic mild hyponatremia is associated with extended hospital stays, functional independence, and increased mortality in individuals with chronic disease and those admitted in the Intensive Care Unit (ICU) settings.[12,23,24,25]

2.

The Role of Dietary Habits in Hyponatremia

Sodium is naturally present in various foods, and its intake can vary based on dietary habits. Familiar sources of dietary sodium include processed and packaged foods, often high in added salt. Table salt, used in cooking or as a seasoning, primarily contributes to sodium intake. Additionally, sodium-rich foods include salty snacks (such as chips and pretzels), canned soups, pickles, cured meats (such as bacon, ham, and sausages), cheese, and certain condiments (like soy sauce). Some natural foods, such as shellfish, dairy products, and vegetables like beets and celery, also provide smaller amounts of sodium.[26] For older adults at risk of hyponatremia it is important to manage the intake of these foods.

• The Impact of Low Sodium Diets on Older Adults
  Lower dietary sodium intake amongst community-dwelling older adults was associated with poorer cognitive function, especially in those over 80. [27] . Cognitive impairments may affect executive functions, potentially impacting intermediate activities of daily living such as financial management. Given the risk of cognitive decline in older adults, even minor changes in cognitive ability because of low sodium intake could have significant health implications. Despite the known benefits of reducing dietary sodium for hypertension, the impact of hyponatremia on cognitive function underscores the need for further investigation.[28,29] Low nutritional sodium levels may negatively influence insulin regulation and the renin-angiotensin and sympathetic systems, potentially affecting cognitive function.[30,31,32] A recent study found a J-shaped relationship between sodium intake, cardiovascular disease and mortality. Individuals consuming more than 6 g of sodium per day and those consuming less than 3 g daily were found to have an increased risk of death and cardiovascular events.[33] Although further research is required, previous studies indicate a potential J-shaped relationship between sodium intake and cognitive function in older adults.[34,35,36] In a recent study involving older adults (average age 70 +- 12 years), adding a low-dose diuretic to angiotensin II receptor blockers for hypertension management significantly lowered serum sodium levels in individuals with low dietary salt intake.[37] As a result reducing dietary sodium intake to low levels may impair an individual's ability to maintain homeostasis, which could result in cognitive changes. This is especially concerning for older adults on medications that effect sodium levels. Reduced sodium intake has also been associated with a higher risk of cardiovascular events and mortality, regardless of blood pressure levels.[23,38]
• Sodium-Rich Foods and Their Effects on Hyponatremia
  Increased sodium intake elevates intra-glomerular pressure, which can contribute to or worsen chronic kidney damage, heightening the risk of progressive kidney disease.[39] High sodium intake is a recognized risk factor for developing such conditions. Specifically, in postmenopausal women in Korea,[36,38] excessive sodium intake (>2000 mg) was found to lead to increased urinary excretion (> 2 g/day), resulting in hypercalciuria and raising the risk of osteoporosis.[40] Additionally, excessive salt consumption has been linked to the development of hypertension[41,42] and, consequently, to a higher risk of cardiovascular disease, particularly in individuals with hypertension and older adults.[23] Lowering sodium intake has been shown to reduce both systolic and diastolic blood pressure, especially in hypertensive and normotensive individuals.[41]
• The Role of Ultra-Processed Foods in Sodium Intake
  The increased availability and consumption of ultra-processed foods has contributed to higher sodium intake in the general population. This increase is beyond the recommended dietary intake of sodium. Ultra-processed foods include packaged snacks, ready-to-eat meals, processed meats, instant noodles, and fast foods. These often contain high levels of added sodium to enhance the flavor and prolong shelf life. [43] This trend is concerning for older adults who have multiple chronic conditions (MCC), as excessive sodium intake from these foods can exacerbate hypertension, cardiovascular disease, and renal impairment.

Consumption of ultra-processed foods could lead to both hyponatremia and hypernatremia, in older adults, especially those with MCC, especially if on multiple medications. Thus, it is crucial for dietary interventions targeting sodium management in to consider reducing ultra-processed food intake while promoting whole, minimally processed foods that support healthier sodium levels and overall nutrition.[43]

3.

Nutritional Deficiencies and Hyponatremia

As people age, their metabolic and organ reserves universally decline. A diet that may be suitable for a young adult could become harmful for the same individual later in life. Failure to adjust diet and lifestyle accordingly can result in maladaptation, where the body struggles to compensate, leading to the development of various chronic conditions common in older adults, such as hypertension (HTN), diabetes (DM), cardiovascular disease (CVS), and chronic kidney disease (CKD).[44] According to the Dietary Guidelines Advisory Committee (DGAC), nearly half of all American adults, approximately 117 million individuals, have one or more chronic diseases that could be prevented with dietary improvements.[45] In an aging population, diet-induced health problems have a more significant impact due to reduced adaptability from age-related metabolic capacity and organ function declines. This contributes to the increased prevalence of chronic conditions like HTN, atherosclerotic vascular diseases, and CKD in older adults. Poor diets are the primary driver of the chronic disease burden in the United States. Currently, only 1% of Americans meet the criteria for ideal CVS health; 46% have HTN, around 50% have prediabetes or DM, and approximately 14% have CKD. Adjusting nutrient intake in the modern diet can mitigate risks of maladaptation, such as acid accumulation, excessive salt intake, potassium (K+) and fiber deficiency, and dehydration, significantly improving overall health.[44]

Salt and water regular are closely intertwined. Serum sodium (Na+) concentration reflects water balance and is the primary determinant of serum osmolality. In the kidney, arginine vasopressin (AVP) and tonicity enhancer element binding protein (TonEBP or NFAT5) work independently and together to maintain regular water absorption, maintaining serum Na+ concentration within the 135-145 mEq/L range. AVP regulates water and retains Na+, affecting volume balance.[44]

The modern diet is deficient in potassium (K+).[46] A low or low-normal serum or plasma K+ concentration resulting from insufficient intake can stimulate kidney NH3/NH4+ production and activate the RAAS, contributing to system inflammation, protein catabolism, CKD development, and, in patients with CKD, accelerating its progression.[47]

Chronic low-grade under-hydration has been linked to impaired cognitive performance, reduced cognition, perceived fatigue, and a lack of energy.[48] Underhydration also increases vulnerability to suboptimal adaptation or maladaptation, leading to kidney dysfunction and other health complications, particularly during physical stress or exposure to hot climates. It is not surprising that chronic under-hydration is also associated with nephrolithiasis,[49] as well as an increased risk of metabolic syndrome and CKD.[44,50,51] Fortunately, studies have shown that the adverse effects of a poor diet can be minimized through dietary modification, specifically by reducing overconsumption of salt and animal products while increasing unrefined plant foods and hydration. Increasing dietary intake of fruits and vegetables enhances both base equivalents and K+ in body fluids, associated with lower blood pressure and reduced risk of CVS diseases, including heart failure (HF) and overall mortality.[23,52,53,54,55,56]

• Protein Energy Malnutrition and Hyponatremia in the Elderly
  Sarcopenia is an age-related decline in skeletal muscle mass and function.[28] The European Working Group on Sarcopenia in Older People (EWGSOP) characterizes sarcopenia as a "progressive and widespread skeletal muscle condition linked to a higher risk of undesirable consequences, such as falls, fractures, physical impairment, and mortality.[57] Sarcopenia has an estimated prevalence of 9 to 18% in people aged sixty-five and older, increasing to 50% in those aged over eighty. Moreover, it has been postulated that beyond 50 years of age, muscle mass is lost at an approximate rate of 1-2% per year.[58] Some of the risk factors for sarcopenia include age, female sex, history of smoking, little to no exercise, particularly endurance training, and specific nutritional deficiencies.[57]

With increasing age, skeletal muscle size and number decrease, including reduced skeletal muscle precursor cells.[59] The causes of sarcopenia are multifaceted. Decreased activity among older people,[59] protein-calorie malnutrition and overnutrition,[19] hormonal declines such as decreased IGF-1, DHEA-sulfate, testosterone, and estrogen levels,[21] and increased inflammatory biomarkers [22] are believed to be critical contributors to the development of sarcopenia. Sarcopenia results in impaired mobility, functional dependence, and increase injury episodes among older adults. Muscle atrophy and decreased muscle strength, especially in the lower limbs, contribute to an increasing incidence of falls, that may result in fractures and other disabilities.[24] Moreover, a higher incidence of functional decline and an increased length of hospitalization are also reported among sarcopenic individuals. Sarcopenia has also been identified as a significant cause of mortality, particularly among those older than seventy-nine.[27]

Sarcopenia has been described as a potential cause of hyponatremia in the literature. Since muscle content represents the body's central potassium reserve, low potassium levels are seen in individuals with sarcopenia. Low potassium content leads to a shift of sodium intracellularly and an inappropriate release of antidiuretic hormone (ADH). These two mechanisms contribute to the development of hyponatremia.[60] On the other hand, hyponatremia may also lead to sarcopenia. As mild hyponatremia is frequently encountered among the geriatric population, its high propensity to cause sarcopenia makes it imperative for physicians to address the condition in a clinical setting.[61] Frailty, closely linked to sarcopenia, is related to hyponatremia, although the mechanism is not well established. Hyponatremia acts as both a causative and a prognostic factor in managing sarcopenia and frailty.[58]

b.

Hyponatremia-Related Deficiencies

Electrolyte abnormalities are observed in a considerable percentage of hyponatremic patients independent of the cause of hyponatremia. In one study, more than half of patients with diuretic-induced hyponatremia exhibited at least one additional electrolyte abnormality.[62] Chronic diuretic usage is frequently associated with hyponatremia, which may also be linked to reduced intracellular potassium reserves. In a small group of patients with chronic congestive heart failure, magnesium replacement alone was sufficient to correct this hyponatremia.[63] The most common disorders associated with hyponatremia include hypophosphatemia, hypokalemia, and hypomagnesemia.

4.

Assessing adequate fluid intake in older adults

There is no simple or universally accepted method for measuring hydration levels in older adults.[64] For example, HF patients may need to check daily weight, along with daily fluid intake and output, to ensure they are not retaining excess fluid. Similarly, individuals with chronic kidney stones must monitor their hydration levels to prevent stone formation, aiming for a daily urine output of 2.5 liters in adults.

5.

Broader Risk Factors and Consideration for Hyponatremia in Older Adults

Age-related physiological changes and dietary factors are key to the development of hyponatremia in older adults. Other significant factors that include hydration status, physical activity, chronic disease, socioeconomic status, healthcare coverage, and education levels.[1] Inadequate hydration can lead to hypernatremia, while excessive fluid intake may cause dilutional hyponatremia, especially in individuals with impaired kidney function or HF. It is important for older adults with impaired renal function or those taking medications that affect fluid balance to maintain a balance between fluid intake and sodium levels.[65]

Sedentary behavior can exacerbate sarcopenia, especially in older adults. [66] Regular physical activity, whether mild or moderate, improves circulation and supports kidney function, aiding in sodium and fluid homeostasis.[67] Chronic diseases are more common in this populations and complicate sodium balance. Medications such as diuretics and antihypertensives, often increase sodium loss. Therefore, fluid management becomes challenging for older adults with MCC.

Social determinants of health significantly impact factors that are essential for managing hyponatremia including access to healthcare services, nutritional counseling, and medications. Older adults from lower socioeconomic backgrounds are less likely to have access to preventative healthcare. Limited or no healthcare coverage further complicates the situation and creates barriers to medical care, including medication reconciliation and dietary consultations. This may delay the diagnosis of hyponatremia resulting in worsening complications.[68] Older adults with lower education levels may need help understanding the steps necessary to maintain sodium balance or how medications can affect their levels.[69] Improving health education, access to health care, and providing adequate health coverage, particularly for vulnerable populations, is crucial to ensure the self-management of chronic diseases.

6.

Screening, Diagnosis, and Management of Hyponatremia in Older Adults

Diagnosing hyponatremia in older adults includes a thorough history. History should include an assessment of food and fluid intake, with particular attention to salt intake and any underlying medical conditions that may contribute to sodium imbalances, such as CHF, liver disease, and renal impairment. Hyponatremia is diagnosed by checking serum sodium concentration. Once a diagnosis of hyponatremia is established, the underlying cause is evaluated by testing urine osmolality and other electrolytes.

Management of hyponatremia includes both the treatment of underlying cause and the sodium imbalance itself. Increasing dietary sodium and protein can benefit patients with mild chronic hyponatremia, especially if their diet is low in sodium intake. Correcting nutritional deficiencies in people with protein malnutrition is necessary for restoring sodium balance and supporting overall health.

For patients with dilutional hyponatremia, the treatment is through fluid restriction. This is especially used for management of patients with hyponatremia due to HF and SIADH, where water retention exacerbates sodium dilution.[65] In more severe cases, such as acute symptomatic hyponatremia, careful administration of hypertonic saline may be required under close medical supervision to avoid complications like osmotic demyelination syndrome.

The prevention of hyponatremia in older adults focuses on dietary education and modification. Older adults should be encouraged to maintain a balanced sodium, protein, and fluid intake while avoiding excessive consumption of processed foods high in sodium. Education on the potential effects of medications, such as diuretics and psychotropic drugs that can alter sodium balance is also crucial.[1] Regular monitoring of sodium levels in high risk individuals, such as those with MCC, may help prevent the development of more severe forms of hyponatremia.

3. Results

This review highlights how dietary habits increase the risk of hyponatremia in older adults. Aging impacts sodium regulation due to physiological changes, like reduced GFR and decreased sodium conversation. These age-related changes are linked to an increased prevalence of hyponatremia, particularly in those with comorbidities such as kidney disease and HF. While low sodium intake is beneficial for managing HTN, it may increase the risk of cognitive decline and impair physical function in older adults. There is a J-shaped relationship between sodium levels and health outcomes, where both very high and very low sodium intake can negatively impact health, particularly in those over 80.

The review also shows how inadequate intake of protein and essential nutrients contributes to conditions like sarcopenia and “tea and toast syndrome”, which exacerbate sodium imbalances and increase susceptibility to hyponatremia. Low potassium levels and sarcopenia can both be cause and consequences of chronic hyponatremia. Additionally, increased consumption of ultra-processed foods is associated with higher sodium intake and adverse health outcomes. For older adults, balancing sodium intake to prevent both, hyponatremia and hypernatremia is crucial, especially given the high prevalence of HTN and CVS disease in the population. Lastly, factors such as hydration, physical activity, chronic disease management, and socioeconomic status play significant roles in incidence an management of hyponatremia in older adults.

There is a complex interplay between dietary habits, nutritional deficiencies, and the risk of hyponatremia in older adults. While low sodium intake and specific nutritional deficiencies contribute to vulnerability, factors such as age-related physiological changes and socioeconomic influences further complicate management strategies.

4. Discussion: Recommendations for Managing Hyponatremia in Older Adults

The findings of this review underscore the complex relationship between dietary habits, nutritional deficiencies, and hyponatremia in older adults. The aging process introduces physiological changes-such as decreased GFR and impaired sodium conservation-that make sodium balance challenging to maintain. Coupled with common dietary patterns, like low sodium and protein intake, older adults face an increased risk of hyponatremia, leading to outcomes that range from cognitive impairment to heightened fall risk. These insights relevel the importance of viewing dietary and nutritional factors as integral component in the prevention and management of hyponatremia.

Managing hyponatremia in this population presents unique challenges. Clinicians must carefully balance sodium intake, particularly in older adults with comorbidities, such as HTN, CKD, and frailty. Polypharmacy further complicates the scenario as diuretics and antidepressants exacerbate sodium depletion. These complexities highlight the need for a nuanced approach, one that considers both dietary sodium intake and broader nutritional factors while navigating the risks associated with high sodium intake for cardiovascular health.

Future strategies in managing hyponatremia should focus on targeted dietary interventions. Emphasizing adequate sodium and protein intake, while limiting ultra-processed foods, may help address the nutritional gaps that increase vulnerability to hyponatremia. Educational initiatives tailored to older adults and caregivers could enhance awareness and adherence to sodium balance guidelines, equipping them with practical strategies for dietary adjustments. An interdisciplinary approach, involving dieticians, physician and caregivers, is also essential, supporting personalized care that reflects each patients unique health status and nutritional needs.

Further research is warranted to refine sodium intake guidelines specifically for geriatric populations. Studies investigating optimal sodium thresholds could help balance the risks of both hypertension and hyponatremia, while also examining how dietary modifications impact sodium balance and overall health in frail older adults. As healthcare costs and aging-related challenges continue to grow, preventive care practices that incorporate dietary education and support, may play a crucial role in mitigating the impact of hyponatremia on quality of life and healthcare systems.

5. Conclusions

In conclusion, this review highlights the multifaceted relationship between dietary habits, nutritional deficiencies, and the development of hyponatremia in older adults. We explored how age-related physiological changes, combined with suboptimal sodium and protein intake, elevate the risk of sodium imbalance, leading to adverse health outcomes, including cognitive decline, falls, and increased morbidity. Effective prevention and management strategies must emphasize personalized dietary education and improved nutritional support tailored to this vulnerable population. By addressing these dietary risks and focusing on sodium and protein adequacy, healthcare providers can contribute to better health outcomes, reduce hospitalizations, and improve the quality of life for older adults. Future research should further investigate targeted dietary interventions to refine preventive care practices and support healthier aging in populations at risk of hyponatremia.