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Role of metformin in people at high risk of diabetes examined

By Nicole MacKee
Metformin may have a long­-term role in staving off the development of diabetes in people at high risk, say researchers who have iden­tified key subgroups who may benefit from medical treatment.

Research published in Diabetes Care showed that treatment with metformin over 15 years reduced the incidence of type 2 diabetes, compared with placebo, by 17% based on glucose levels or 36% based on HbA1c levels below 6.5%. Effects were great­est for women with a history of gestational diabetes and for people with higher baseline fasting glucose or HbA1c levels.

In the study, researchers analysed data from the US Diabetes Prevention Program (DPP) data (1996­2001) and the subsequent Diabetes Prevention Program Outcomes Study (DPPOS; 2002­ present).

During the DPP, adults at high risk of developing diabetes were randomly assigned to masked placebo (1802 participants) or metformin 850mg twice daily (1073 participants). Participants originally assigned to metformin continued to take the drug, unmasked, during the subsequent study.

The researchers cautioned that these findings must be consid­ered carefully because original eligibility and diabetes development criteria were based on glucose levels and not HbA1c.

Associate Professor Neale Cohen, Director of Clinical Diabetes at the Baker Heart and Diabetes Institute, Melbourne, said it was helpful to identify patient groups who may benefit from metformin, but its use in prediabetes remained controversial. In Australia, metformin is not approved for use for patients with prediabetes.

‘One of the main issues about prediabetes is that it affects about a quarter of the population. So, rolling out a medication for an entire population of that size ... would have an enormous cost, even though metformin is not an expensive drug,’ Associate Professor Cohen told Endocrinology Today.

‘I think the view of most clinicians would be that people at high risk of developing diabetes should be given lifestyle instruc­tions,’ he said. ‘If it’s not possible for people to make lifestyle changes – let’s say they can’t exercise often or their diet is already quite good – then you could certainly consider metformin in that context.’

However, he added, that improving lifestyle was effective in people who had already developed diabetes.

‘We have some diet­-controlled patients with diabetes who are doing pretty well without metformin,’ Associate Professor Cohen said. ‘Lifestyle change is tremendously important in the prediabetes sphere, so I think that’s where we should concentrate most of our efforts at the moment.’
Diabetes Care 2019; 42: 601-608.