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Continuous glucose monitoring in type 2 diabetes and beyond

5th April 2023

People with type 2 diabetes often start on non-insulin glucose-lowering medication but, as their condition progresses, they may need insulin. Dr Lalantha Leelarathna, consultant diabetologist at the Manchester Diabetes Centre, spoke about the use of CGM in people with type 2 diabetes who are on basal insulin. For instance, one study looked at the Dexcom G7 compared with self-monitoring of blood glucose (SMBG) in participants with above-target HbA1c and found a mean reduction of 0.5% in those on CGM compared with SMBG. There was also more weight loss in the CGM group. “So we are already beginning to see that CGM is training people to change their behaviour,” he said. “This is leading to better outcomes without having to escalate treatment.”

The MOBILE study

MOBILE is the seminal study in this area and it was carried out in primary care in the US using a Dexcom G6 CGM, with participants whose HbA1c was between 62 and 102 mmol/mol. “I want to emphasise that this study recruited a very ethnically diverse group, with 53% non-Caucasian participants,” said Dr Leelarathna. “The baseline profile also showed that time in range [TIR] was a mean of 40%, so around three hours in hyperglycaemia. But, interestingly, glucose variability was low at 28%, so they were running high.”

The findings of MOBILE showed a significant decrease in HbA1c of 0.5% (5.5 mmol/mol) for those on CGM compared with SMBG. TIR was 59% versus 43%, 11% versus 27% in hyperglycaemia and 0.2% versus 0.5% in hypoglycaemia.

There have also been a few real-world studies using the Freestyle Libre CGM with basal insulin users, which also show findings heading in the right direction.

Cost-effectiveness of CGM in type 2

Of course, CGM has to be paid for and healthcare systems are only just getting used to the cost of rolling out the technology to people with type 1 diabetes. There are far more people with type 2 diabetes, although only a minority are on insulin. However, if CGM is shown to improve outcomes, it could be a good investment in type 2 diabetes as well.

Dr Leelarathna cited a study on cost-effectiveness, using US data adapted to a UK and NHS perspective. This calculated a cost of £3684 per quality-adjusted life year (QALY) for real-time CGM and £5781 for intermittent (flash) CGM. This, he said, would come in well below the threshold that the National Institute for Health and Care Excellence (NICE) considers to be value for money.   

Of course, further research into CGM in type 2 diabetes is still needed. For instance, there are few SGLT-2 inhibitor, GLP-1 receptor agonist or non-insulin users in studies. It would also be interesting to know how CGM affects lifestyle – sleep, diet, exercise and medication adherence – as well as acute complications, quality of life and other patient-reported outcomes.

Further research on subgroups according to ethnicity, social deprivation and younger onset diabetes should also be on the type 2 diabetes CGM agenda. Work also needs to be done on easier access to CGM data, including its application in titration of insulin dose and therapy change. “We need to simplify how data is visualised because these groups are managed in primary care,” said Dr Leelarathna. “The benefits of CGM may come from lifestyle modification. Now we need further work to extract the full potential of CGM in the type 2 diabetes journey.”

CGM for non-insulin users too?

Dr Richard Bergenstal, consultant endocrinologist at the University of Minnesota, focused on what CGM can do for people with type 2 diabetes who are not on insulin. For instance, the IMMEDIATE study, which has just reported, randomised 116 individuals with HbA1c ≥58 mmol/mol to either Flash monitoring plus diabetes self-management education (DSME) or DSME alone. The trial lasted 16 weeks and participants wore a blinded CGM on the first 14 and last 14 days of the trial so that their TIR could be measured. Those using Flash plus DSME improved their TIR by 9.9% (2.4 hours), with a mean HbA1c reduction of 3 mmol/mol, compared with DSME alone. Other studies are also going in the right direction, showing improvements in glycaemic control.

Meanwhile, a survey of 306 people with type 2 diabetes showed that 93% were willing to do more to manage their condition and singled out food choices and TIR as good ways of helping them to do this. “CGM could fill that role,” said Dr Bergenstal. He referred to some pilot data showing that people with type 2 all have different glucose responses to the same meal because they belong to different glucotypes and could be helped by a personalised or precision nutrition approach. “We really need CGM to sort this out because we can’t just say ‘eat this food’”, he said. 

Real-world data can also be revealing. Dexcom has thousands of people in its database. A study of 7000 people with type 2 diabetes who were not on insulin showed that their TIR was 70%. There was also a high level of engagement with the CGM, as seen by the number of screen views, although data was not shared as much as in type 1 diabetes.

The personal value of CGM in type 2

Meanwhile, research at Dr Bergenstal’s centre shows how important it is for people to know their targets, look at their food choices to see how they respond and, if they need to, make changes. “This is the value of CGM – you see it every day,” he said. “We call it ‘know, learn and adjust’ or you might call it ‘not treat to target, but eat to target’. And it’s not just about glucose targets and eating healthily. A healthy eating pattern has as strong a link with morbidity and mortality as a lower HbA1c or glucose management indicator (GMI).”

He has heard people say the following about CGM: “Please, listen to me, it changed my life”; “I finally know what to eat and how much to eat”; “For me, it’s the start of taking control of my health”.

So what data do we now need? “I think we need to define how this whole relationship of GMI and HbA1c align in diabetes management because we’re not going to use CGM early in diabetes management if we don’t know what the metrics are,” said Dr Bergenstal.

GMI can be seen as personalised HbA1c, but is HbA1c still the gold standard? The American Diabetes Association says it should be measured twice a year but then, in 2021, they mention other glycaemic measures. Now, in 2022/23, it is HbA1c, GMI or TIR. “So the guidelines have gone from ‘and’ to ‘or’,” Dr Bergenstal observed. 

Towards wider use of CGM

Looking at CGM in a broader context, it can also be used to decide whether to prescribe SGLT-2 inhibitors or GLP-1 receptor agonists, which are now recommended for many with type 2 diabetes. Since the introduction of CGM, GLP-1 receptor agonists have been prescribed more often and this is likely to continue. “I predict that CGM is going to be part of diabetes management and support for all people striving to live well with diabetes,” Dr Bergenstal concluded.

Dr Satish Garg, endocrinology and paediatric specialist at the Barbara Davis Centre, University of Colorado, said, “sensors have come a long way.” The FDA now has guidelines for intraoperable CGM approval. There are eight million users of CGM in the US with a market value of $8 billion and this is expected to grow exponentially in the next few years. “In future, with GLP and GIP agonists, the need for insulin in type 2 diabetes will continue to go down,” he continued. “And we will be able to use CGM to diagnose diabetes at a much earlier stage.”

He went on to give clinical examples of how CGM profiles have already been used successfully to diagnose diabetes, study prediabetes and monitor the impact of therapies. He believes that CGM will eventually replace fingerprick testing of blood glucose altogether. “There could even be a case for using CGM in healthy individuals as a vital sign, like blood pressure and pulse,” he concluded. 

Any opinions expressed in this article are the responsibility of the EASD e-Learning Programme Director, Dr Eleanor D Kennedy.