In Depth

Prediabetes: a “useless label” or an important method of prevention?

Some would argue that prediabetes is a useless label, or even a cynical one. Others would argue that it is a helpful diagnostic tool, a largely successful way to encourage people at risk of type 2 diabetes to adopt a healthier lifestyle. Whichever view is correct, what’s indisputable is that prediabetes is one of the more controversial terms in healthcare today.

Type 2 diabetesis, in many cases, a preventable condition. Aside from those cases caused by genetics and polycystic ovary syndrome (PCOS), type 2 diabetes is usually caused at least in part by an unhealthy diet and a lack of exercise. It makes sense, then, that we would attempt to stop type 2 diabetes developing before it’s too late, and prediabetes is the best way we’ve come up with to do that.

The benefits of prediabetes

To many, this is a positive thing. Barbara Young, chief executive of Diabetes UK, has said of prediabetes:

“Being identified as having pre-diabetes, borderline diabetes or being at high risk provides an opportunity for those people who have a major chance of developing type 2 diabetes, a lifelong condition which is associated with extremely serious complications such as blindness and stroke, to walk away from it.”

When put that way, the benefits are obvious. Prediabetes creates motivation to change. An official diagnosis invites serious discussion between patient and doctor. People who might not know much about how their diet and lifestyle choices affect their health are provided an environment in which to learn. But there is an ever-increasing number of sceptical voices who find the label of prediabetes less than helpful, for several reasons.

Prediabetes and exercise

Those in favour of the prediabetes label argue that it encourages people to make lifestyle changes.

A meaningless label?

One such argument suggests that prediabetes is a meaningless label, creating medical conditions that aren’t actually medical conditions. Many people diagnosed with prediabetes are actually healthy; they don’t have a disease. They’re being diagnosed with a condition they might get one day, but just as likely won’t. It’s hard to put an exact figure on it, but research suggests that less than half of people diagnosed with “prediabetes” would ever go on to develop type 2 – even without interventions.

There is an ever-increasing number of sceptical voices who find the label of prediabetes less than helpful, for several reasons.

The problems with prediabetes were explored in a high-profile study in the BMJ, which described prediabetes as “unhelpful and unnecessary.” One of its authors, Professor John Yudkin of University College London, told BBC News: “Prediabetes is an artificial category with virtually zero clinical relevance.”

“There is no proven benefit of giving diabetes treatment drugs to people in this category before they develop diabetes, particularly since many of them would not go on to develop diabetes anyway.

“More people are being included in the medical category of prediabetes without the evidence that they are going to benefit from the interventions.”

The end result is a population over-diagnosed with diseases that aren’t diseases, something which would be less problematic if more people would actually have gone on to develop type 2 diabetes.

Prediabetes, drugs, metformin

People with prediabetes are usually given glucose-lowering medication such as Metformin. Some critics argue that prediabetes is primarily an excuse to push more people onto medication.

Diagnosing prediabetes

The inaccuracy of prediabetes screening techniques suggests that the problem is with the diagnostic methods themselves. Prediabetes is diagnosed in three ways: a fasting glucose tolerance test; a “drink” test; or an HbA1c test. Any one of these tests can land you with a diagnosis of prediabetes. Although diagnostic methods for prediabetes are improving – recently, scientists developed a blood test for fatty acids – these three methods remain the most dominant. And flawed. As Edwin Gayle, emeritus professor of diabetic medicine at the University of Bristol, says:

“One of the problems with prediabetes is that there are three doors in [but] there aren’t actually any doors out. There’s no official way of being undiagnosed with prediabetes. Now, if all three measures correlated 100 per cent there would be no problem, but in fact, they overlap very weakly. For example, fasting blood glucose overlaps by only about 30 per cent with the definition of diabetes in terms of glucose tolerance test. So, the result of having this very wide net is that you’re catching an awful lot of fish, and you’re not necessarily catching the people you want to catch.”

There are also disagreements about whether or not a diagnosis of prediabetes is motivating or dispiriting. Simon O’Neil, of Diabetes UK, believes it’s the latter: “When we’ve spoken to people about it, the problem is they seem to think that means they’re diagnosed with diabetes. They’re just diagnosed a bit earlier, and it’s sort of inevitable that they will go on to develop [type 2] diabetes. Of course, that’s not the case – only five to ten per cent of people who fall into a prediabetic range will actually develop type 2 diabetes in the following year.”

If prediabetes is such a limited, flawed concept, how should we replace it? The consensus, it seems, is that a new label should be more flexible. Currently, the same blanket thresholds are applied to everybody, regardless of natural mitigating factors such as age. Whether you’re a 30-year-old heavy smoker with an unhealthy diet or a fit and healthy 80-year-old whose blood sugars are naturally increasing, the label remains the same.

Currently, the same blanket thresholds are applied to everybody, regardless of natural mitigating factors such as age. Whether you’re a 30-year-old heavy smoker with an unhealthy diet or a fit and healthy 80-year-old whose blood sugars are naturally increasing, the label remains the same.

“Telling someone they’ve got [high] blood glucose levels at the age of 30 is actually something that can make a huge difference to their life and that they can do a lot about,” said Dr. Gayle. “But there’s in fact no evidence that in the elderly person, as against the young person, that intervention will be helpful.

“My grouse […] is that we have a diagnosis and a guideline based on a one-size-fits-all number. It’s ludicrous to give a single number for every member of the population, and I think that’s the entire problem.”

Moreover, prediabetic status can vary depending on where you live. In the UK we have a different threshold to the USA – 6.0 to 6.4 per cent HbA1c in the UK, compared to 5.7 to 6.4 per cent HbA1c in the US – so a person in one country could have a condition that requires medication, and a person in the other country could not – despite having the same HbA1c levels.

Is labelling people with prediabetes cynically motivated?

The problem, then, seems simple: we need a label, our current one is flawed – we need to come up with a new, more flexible label. So why hasn’t this happened? According to somen, the reasons are sinister. Dr.Yudkin’s study suggests that the only people to benefit from the prediabetes problem are pharmaceutical companies.

“I am concerned about the rising influence of the term,” said Dr.Yudkin. “It has been used in many scientific papers across the world, and has been applied to a third of adults in the UK and half of those in China. We need to stop looking at this as a clinical problem with pharmaceutical solutions and focus on improving public health. The whole population would benefit from a more healthy diet and more physical activity, so it makes no sense to single out so many people and tell them that they have a disease.”

Appearing on BBC Radio 4’s Inside Health, Margaret McCartney expressed her own suspicions with the label of prediabetes:

“I have to say I’m very suspicious of the medical industry’s desire to have more and more people categorised with having “pre-something.” We’ve seen it with “pre-dementia,” we’ve seen it with “pre-hypertensio,” and this, I think, is yet another instance of criteria being brought down, more people caught in the net, and the question is how many people will benefit from an earlier diagnosis of something that may never happen to them.”

Type 2 diabetes is a preventable condition, and it’s important to have a process in place to screen those at high risk so that they can make changes to their lifestyle before it’s too late. In its current state, however, prediabetes is clearly flawed. Rather than seeing the debate about prediabetes as a simple binary – to keep it or get rid of it – the best solution might be to tweak the prediabetes label, to make it more flexible and accommodating so that it’s more tailored to individual situations. Whether we’ll ever see those changes as long as so many people are on glucose-lowering medications is another matter.

 

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