Association between metformin and abdominal aortic aneurysm in diabetic and non-diabetic US veterans

We sought to examine the progression from abdominal aortic aneurysm (AAA) diagnosis to surgery and death among diabetics with and without exposure to metformin as well as non-diabetics. We conducted a retrospective cohort study (January 2000 to July 2019) comparing 3 transitions (AAA surgery, death, and death after AAA surgery) among propensity score-matched metformin-exposed and unexposed diabetic veterans and non-diabetic veterans using the VA Informatics and Computing Infrastructure database. We fit an adjusted Cox proportional hazards model with transition-specific effects. There were 43,073 metformin-unexposed diabetics, 24,361 metformin-exposed diabetics and 56,006 non-diabetics. Compared with the non-diabetic cohort, both diabetic cohorts have a lower risk of surgery (no metformin (HR=0.740, 95% CI 0.706 to 0.776); with metformin (HR=0.770, 95% CI 0.730 to 0.813)). However, the non-metformin diabetic cohort has a higher risk of death (HR=1.024, 95% CI 1.004 to 1.045) and death after surgery (HR=1.086, 95% CI 1.013 to 1.165). The metformin-exposed diabetic cohort has a lower risk of death in the first 10 years after AAA diagnosis (HR=0.877, 95% CI 0.855 to 0.899), yet a higher risk of death 10 years after AAA diagnosis (HR=1.177, 95% CI 1.092 to 1.270) compared with non-diabetic cohort. Non-diabetics have the highest rate of AAA surgery compared with both diabetic cohorts. However, diabetics without metformin have the highest risk of death prior to, and after surgery. This research provides novel findings for patients diagnosed with AAA. The use of metformin after both AAA diagnosis and surgery should be further investigated.