All-cause mortality in patients on sulphonylurea monotherapy compared to metformin monotherapy in a nation-wide cohort

Background: Type 2 diabetes is associated with increased mortality. There is some data that sulphonylurea therapy may contribute to this.

Aims: To compare all-cause 3-year mortality of patients on sulphonylurea monotherapy to that of patients on metformin monotherapy after adjusting for potential confounders.

Methods: We searched the Maltese national electronic database for diabetes treatment in April 2014. This is an electronic database of all treatment that patients are prescribed through the local National Health Service. We identified patients on metformin or sulphonylurea monotherapy and linked this to the national mortality database and the laboratory information system.

Results: There were 25,792 persons who were on treatment for diabetes in April 2014. Of these, 9977 were on metformin monotherapy and 1717 on sulphonylurea monotherapy. This cohort was followed up until April 2017. There were 2518 deaths (9.76%) during this period, giving an average of 32.5 deaths per 1000 persons with diabetes. Logistic regression showed that persons on sulphonylurea monotherapy were 2.03 (95% CI 1.68-2.44, p < .001) times more likely to die within 3 years than persons on metformin monotherapy, after adjusting for age, eGFR and HbA1c. The logistic regression model was statistically significant, p < .001. Additional adjustment for LDL-cholesterol, HDL-cholesterol and urinary albumin-creatinine ratio did not alter the results.

Conclusion: Our data shows that sulphonylurea monotherapy is associated with higher all-cause mortality when compared to metformin monotherapy after adjusting for potential confounders.