Inverse association between glucose-lowering medications and severe hyponatremia: a Swedish population-based case-control study

CONTEXT: Glucose-lowering medications have occasionally been reported to cause hyponatremia, but the evidence is scarce. OBJECTIVES: To explore the association between glucose-lowering medications and severe hyponatremia. DESIGN, SETTING, AND PARTICIPANTS: Subjects hospitalized with a principal diagnosis of hyponatremia (n = 14,359) were compared with matched controls (n = 57,383). Data were derived by linkage of national population-based registers. Multivariable logistic regression adjusting for co-medication, diseases, previous hospitalizations, and socioeconomic factors was used to explore the association between hospitalization for hyponatremia and the use of different glucose-lowering medications. Furthermore, newly initiated (≤90 days) and ongoing use was investigated separately. MAIN OUTCOME MEASURES: Hospitalization due to hyponatremia. RESULTS: The unadjusted ORs (95% CI) for hospitalization due to hyponatremia were 1.41 (1.29-1.54) for insulins, 1.38 (1.27-1.50) for metformin, and 1.22 (1.07-1.38) for sulfonylureas. However, after adjustment for confounding factors the association was consistently reversed. Thus, for any glucose-lowering medication the adjusted OR was 0.63 (0.58-0.68). For insulins, metformin and sulfonylureas, adjusted ORs (95% CI) were 0.58 (0.52-0.65), 0.81 (0.72-0.90) and 0.81 (0.69-0.94), respectively. Odds ratios for newly initated medications were overall higher while those for ongoing treatment were further decreased. Thus, adjusted ORs (95% CI) for ongoing treatment with insulins, metformin, and sulfonylureas were 0.54 (0.48-0.61), 0.82 (0.73-0.91) and 0.78 (0.66-0.92). CONCLUSIONS: Glucose-lowering medications did not increase the risk for hospitalization due to severe hyponatremia. In fact, the association was inverse across all investigated drugs. The association may be mediated by pharmacologic mechanisms, but the uniform effects across drug-classes suggest properties of the diabetic disease are of importance.