Scientists have made surprising findings from a major study of more than 400 000 healthy adults indicating that even sodium levels within the high end of the normal range may be linked to an increased risk of hypertension and heart failure.
The team from Bar-Ilan University found that people with sodium at the upper end of the normal range were found to be significantly more likely to develop high blood pressure and heart failure, two of the most common chronic diseases as we age.
The research examined electronic health records spanning 20 years, from 2003 to 2023, covering more than 407 000 healthy adults who receive care through Leumit Healthcare Services, one of Israel’s top health providers. It is one of the largest and most detailed studies ever to explore how hydration levels may impact long-term heart health.
The findings were published in the European Journal of Preventive Cardiology.
Among the key findings:
• Sodium levels of 140–142 mmol/L (still within normal range) were linked to a 13% higher risk of hypertension;
• Levels above 143 mmol/L were associated with a 29% higher hypertension risk and 20% higher risk of heart failure; and
• Nearly 60% of the healthy adult population had sodium levels in these risk-associated ranges.
Sodium, which is routinely tested in standard blood tests, has long been considered normal within the 135–146 mmol/L range. But this study challenges that assumption, suggesting a strong, long-term association between higher sodium levels and cardiovascular risk, even among those considered otherwise healthy.
Controlled for confounding variables
These associations remained strong even after adjusting for age, sex, BMI, blood pressure, smoking and potassium levels. The analysis excluded individuals with conditions that affect water balance to ensure a more accurate reflection of hydration-related risk.
“Our findings point to hydration as a critical and overlooked part of chronic disease prevention. A simple blood test might flag people who could benefit from basic lifestyle adjustments – like drinking more water, which reduces sodium levels,” said the study’s lead author, Professor Jonathan Rabinowitz, from the Weisfeld School of Social Work at Bar-Ilan University. Rabinowitz collaborated on the research with Dr Natalia Dmitrieva, from the National Institutes of Health (NIH).
“This study adds compelling evidence that staying well-hydrated may help reduce the long-term risk of serious conditions like hypertension and heart failure.”
With population ageing and chronic disease rates on the rise, these insights may inform future clinical guidelines, preventive screenings, and public health campaigns aimed at encouraging healthy hydration habits.
Study details
Risk of hypertension and heart failure linked to high-normal serum sodium and tonicity in general healthcare electronic medical records
Jonathan Rabinowitz, Mahmoud Darawshi, Nuriel Burak, Manfred Boehm and Natalia Dmitrieva.
Published in European Journal of Preventive Cardiology on 11 April 2025 .
Abstract
Aims
Population ageing is fuelling an epidemic of age-related chronic diseases. Managing risk factors and lifestyle interventions have proven effective in disease prevention. Recent epidemiological studies have suggested poor hydration as a modifiable risk factor, linked to a higher risk of chronic diseases. We evaluate whether hydration-related markers, serum sodium and tonicity, can serve as risk factors for hypertension and heart failure informing hydration-focused interventions in general healthcare.
Methods and results
We analysed 407 187 adults (18–104 years) from 20-year electronic medical records from Israel’s Leumit Healthcare Services. We included individuals without significant chronic diseases and water balance issues, having normal serum sodium (135–146 mmol/L). Cox proportional hazards models were used to assess the risk of developing hypertension and heart failure. Our analysis showed an increased risk of hypertension with higher serum sodium levels: a 13% rise at 140–142 mmol/L and 29% for levels above 143 mmol/L [hazard ratio (HR) 1.29, 95% confidence interval (CI): 1.25–1.33]. Tonicity over 287 mosmol/kg was associated with a 19% increased risk of hypertension (HR 1.19, 95% CI: 1.17–1.22). The risk of heart failure also increased, reaching 20% for sodium above 143 mmol/L (HR 1.20, 95% CI: 1.12–1.29) and 15% for tonicity above 289 mosmol/kg (HR 1.16, 95% CI: 1.08–1.21). Among current healthy Leumit members, 19% had serum sodium within the 143–146 mmol/L range and 39% were in the 140–142 mmol/L range.
Conclusion
A serum sodium and tonicity exceeding 140 mmol/L and 287 mosmol/kg are associated with increased risk of hypertension and heart failure in the general Israeli population. These thresholds could be used to identify individuals at risk, warranting additional clinical evaluations and guiding preventive intervention.
See more from MedicalBrief archives:
Hydration may slow cardiac decline and reduce heart failure risk – NIH study
Sodium content policy change can save 7m lives – WHO