Effect of dysmagnesaemia and its correction on mortality of non-critically ill hospitalized medical patients

Magnesium is an essential electrolyte, regulating enzymatic function and membrane excitability. While dysmagnesaemia is common among hospitalized patients, its prognostic role and the potential clinical benefit of its correction remain debated. Methods: All adult patients admitted to internal medicine wards at the Tel-Aviv Sourasky Medical Center between June 1^st, 2007, and July 31^st, 2022, for whom magnesium levels were measured, were included. Data from 85,466 patients were obtained. Patients were divided into four subgroups according to magnesium level at admission: severe hypomagnesaemia (serum magnesium ≤1.2mg/dL), mild hypomagnesaemia (magnesium >1.2mg/dL≤1.8mg/dL), eumagnesaemia (magnesium >1.8/≤2.55mg/dL), and hypermagnesaemia (magnesium >2.55). The primary outcome was 30-day mortality risk. Results: Hypomagnesaemia was associated with the use of thiazides and proton pump inhibitors (p<0.001), while severe hypermagnesaemia was associated with reduced renal function (p<0.001). After adjusting for age, gender, the Charlson comorbidity index, creatinine, potassium, and calcium corrected for albumin, mild hypomagnesaemia was associated with lower 30-day mortality (HR: 0.87, 95% CI: 0.82-0.93, p<0.001), hypermagnesaemia was associated with higher 30-day mortality (HR: 2.86, 95% CI: 2.57-3.17, p<0.001), and severe hypomagnesaemia was not associated with survival change (HR: 0.82, 95% CI: 0.62-1.09, p=0.177). Hypermagnesaemia normalization (HR: 0.77, 95% CI: 0.63-0.93, p<0.001) and administration of magnesium supplements for mild (adjusted HR: 0.53, 95% CI: 0.36-0.79, p=0.002) or severe (HR: 0.34, 95% CI: 0.28-0.41, p<0.001) hypomagnesaemia were associated with reduced mortality. Conclusion: In hospitalized, non-critically ill medical patients, hypermagnesaemia confers a substantial 30-day mortality risk, which may be mitigated by its correction. Although hypomagnesaemia is not associated with worse outcome, its correction by supplementation may be of clinical benefit.