medwireNews: Study results suggest that prolonged use of metformin by people with type 2 diabetes may reduce their risk for being hospitalized with heart failure.
The retrospective analysis by Chin‐Hsiao Tseng (National Taiwan University Hospital, Taipei) compared heart failure hospitalization rates among 41,909 people with type 2 diabetes who had ever used metformin and an equal number who had never used the medication but were matched for their propensity to be prescribed it.
Tseng found a dose–response relationship between duration of metformin use and risk for heart failure hospitalization.
Compared with never using metformin, heart failure hospitalization risk was not affected by less than 29.5 months of metformin use (approximately 2.5 years; the lowest tertile), but was reduced by a significant 42.5% with 29.5–61.6 months’ use and by 67.3% with more than 61.6 months of use.
Within the matched cohort, people taking metformin were slightly but significantly younger than never users, at 65.28 versus 64.96 years, but the relationship between metformin and heart failure risk was demonstrable in people younger than 65 years as well as in older people.
Metformin users were slightly but significantly less likely than never users to be using sulfonylureas (77.1 vs 78.8%) or acarbose (10.1 vs 10.8%), but there were no differences for other diabetes medications, or for other medications such as hypertensive agents.
Tseng drew the study data from Taiwan’s National Health Insurance database, covering the period from 2006 to 2011. He notes that “the data might seem to be a little old,” but stresses that this makes the results less likely to be confounded by modern diabetes medications with proven cardiovascular benefits. Sodium-glucose cotransporter (SGLT)2 inhibitors were not available in this time period, while incretin-based medications were becoming available, but the relationship between metformin and heart failure risk remained after excluding people who had received these medications.
The cardioprotective effects of SGLT2 inhibitors are apparent over relatively short-term use, says Tseng, contrasting with the late effect associated with metformin use in this study.
“Therefore, an early and continuous use of metformin in combination with later add‐on of sodium glucose cotransporter 2 inhibitors if more effective glycemic control is required will probably provide a consistent protection against [heart failure] in patients with type 2 diabetes,” he writes in the Journal of the American Heart Association.
Tseng concludes: “Because metformin is inexpensive and safe and would not cause hypoglycemia when used as monotherapy, its protection against [heart failure] is worthy of more extensive investigation in both patients with diabetes mellitus and people without diabetes mellitus.”
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