One class of drug used to treat type 2 diabetes may not reduce the risk of death when compared with placebo, suggests new findings.

The research, led by scientists from Imperial College London and published in the Journal of the American Medical Association, studied three types of diabetes treatment: sodium-glucose cotransporter 2 (SGLT-2) inhibitors, glucagon-like peptide 1 (GLP-1) agonists, and dipeptidyl peptidase 4 (DPP-4) inhibitors. Previous studies suggest these treatments are currently prescribed to at least one in three people with type 2 diabetes.

The team investigated whether these drugs were associated with a lower mortality risk, and conducted a network meta-analysis of 236 trials comparing all the drugs against each other, a placebo, or no treatment at all, and involving 176,310 patients.

All the drugs lower blood sugar levels but the results revealed that while two of the drugs reduced the risk of death when compared with a placebo, one did not.

The results revealed that SGLT-2 inhibitor drugs were associated with a 20% reduction in risk of death, compared to patients taking an inactive placebo pill, or people taking no medication at all.

The class of GLP-1 agonist drugs meanwhile reduced risk of death by 18%.

However the DPP-4 inhibitor drugs were not associated with a reduced risk of mortality compared to people taking placebo or no treatment at all. Furthermore, SGLT-2 inhibitor drugs and GLP-1 agonist drugs reduced the risk of death compared with DPP-4 inhibitor drugs. There was no significant difference between the SGLT-2 inhibitor and GLP-1 agonist drugs.

Dr. Sean Zheng, lead author of the study from National Heart and Lung Institute at Imperial, said: “Type 2 diabetes has become a global epidemic, with more cases than ever before. The three drug classes assessed here are being increasingly prescribed, yet until now there have been no clinical trials studying how these drugs compare to each other, and which type of drug could be the best option for patients.”