1492127928976 - The pre-diabetes tidal wave – harbinger of doom or symptom of an overdiagnosis epidemic?

The pre-diabetes tidal wave – harbinger of doom or symptom of an overdiagnosis epidemic?

On the numbers, a quarter of adult Kiwis have it. And that’s about where the consensus ends.

Suddenly, pre-diabetes appears everywhere – the subject of newly funded New Zealand research projects and endless international papers. 

Fans of the label herald it as a golden opportunity to get in early, shocking people into lifestyle change to stem the swelling wave of diabetes that threatens to cripple both its sufferers and the health system. But it’s not quite that straight-forward.

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When anti-junk-food campaigner Gareth Morgan was told he had pre-diabetes about four years ago, he found it “like saying you’ve now got cancer – that’s what it feels like. Because up until then, I’d been perfect – indestructible.”

The trouble is, pre-diabetes is not like cancer at all. It’s not even a disease. And there’s little consensus on just how many patients slapped with the label – or which of them – will progress to the damaging type 2 diabetes people justifiably fear.

Critics argue the label is another symptom of an epidemic of overdiagnosis. A 2014 paper in the British Medical Journal, which said the pre-diabetes label was “turning healthy people into patients”, quoted writer Aldous Huxley: “Medical science has made such tremendous progress that there is hardly a healthy human left.”

In New Zealand, pre-diabetes is determined by blood sugar levels, which don’t take into account other diabetes risk factors such as family history and ethnicity. PHOTO: GETTY IMAGES

What is pre-diabetes?

In New Zealand, pre-diabetes is determined by blood sugar levels, measured as part of routine cardiovascular risk checks since 2003. The current screening test, called Hba1c, was approved in 2011.

An Hba1c level of 40 or less is deemed normal, 41-49 is pre-diabetic and anything above 50 is diabetic. But everyone agrees the cutoff points are completely arbitrary.

Here’s an analogy. Imagine meteorologists classify cool, warm and hot days. They decide any day averaging 20°C or less is “cool”. An average of 21-29°C is “warm”, while “hot” is 30°C or above. 

Being told you have pre-diabetes is a bit like trying to assess your sunburn risk on a “warm” day. You’re more likely to fry at 29°C than at 21°C, so if forecasters only tell you the day will be “warm”, it will be hard to predict your true risk. And if the temperature is 21°C, the sunburn risk won’t be significantly greater than for a 20°C day, even though one is deemed “warm” and the other “cool”.

Measuring temperature alone also ignores other important influences: environmental variables such as cloud cover and shade; and factors personal to you – what you’re wearing and your skin type.

Experts report that the fear-factor of a pre-diabetes diagnosis can be what’s needed to motivate lifestyle change.

IS PRE-DIABETES A SURE PREDICTOR OF FUTURE DIABETES?

The basic requirement for good, ethical screening is a test that is both sensitive – meaning it correctly identifies everyone at risk; and specific – meaning it avoids false positives.  

A 2017 British Medical Journal analysis found the Hba1c test was neither – it both labelled people who would not go on to develop diabetes, and failed to identify others who would.

“As screening is inaccurate, many people will receive an incorrect diagnosis and be referred on for interventions while others will be falsely reassured and not offered the intervention. These findings suggest that ‘screen and treat’ policies alone are unlikely to have a substantial impact on the worsening epidemic of type 2 diabetes,” the study authors concluded.

It’s commonly quoted that up to 70 per cent of people with pre-diabetes progress to diabetes. But that figure appears to come from one 2001 study, and is based on a tiny subset of 20 patients identified as pre-diabetic by both of two lesser-used tests.

The best guess for the Hba1c test is that 2 per cent of people with pre-diabetes will progress to diabetes every year.

The catch? “We don’t know which is which,” says Les Toop, a Christchurch GP and Otago University professor of general practice. A pre-diabetic level of 41 today can drop to 39 (normal) six months later, with no intervention. Or a level of 44 might rocket to 54 (diabetic) next year.

It’s like the hugely contentious PSA screening for prostate cancer, in which symptom-free men get intensive treatment for a condition that may never have caused problems. And, like PSA testing, Hba1c testing has become a screening programme by default, without any evaluation.

Critics of the pre-diabetes label argue it medicalises people who may not go on to develop diabetes.

Toop doesn’t use the pre-diabetes label. Instead, he explains high blood sugar is bad for your blood vessels, and the higher it is, the worse it is.

“I don’t say ‘You’ve got pre-diabetes – you’re going to get diabetes’. I absolutely don’t. Because apart from anything else, that’s not true for half the people, they’re not going to do that. You are scaring them unnecessarily.”

He’s not against screening high-risk groups, such as Pasifika people, who get very high, damaging sugar levels very early. The difficulty is when doctors code pre-diabetes as an illness, Toop says.

“It’s the same as if you diagnose mild depression – which is probably just unhappiness – as depression. It can have major life implications for employment, life insurance and so on.”

Southern Cross health insurance says new clients declaring pre-diabetes would not be covered for future diabetes treatment, but might still be covered for future heart disease.

Professor Rod Jackson, a cardiovascular risk expert, also avoids the pre-diabetes tag, as it goes against the holistic approach to risk assessment. They’ve also stopped labelling people with high blood pressure as “hypertensive”, as research found it had negative effects, because it medicalised otherwise healthy people.

If you give people a label, there’s a risk they’ll give up, thinking they already have a disease, Jackson says. He also worries that drug companies are behind the pre-diabetes diagnosis, creating a patient base for future drugs.

“I don’t know where it’s come from, but it’s a retrograde step. It’s become everywhere. And if something’s everywhere, I think it’s being pushed by the pharmaceutical industry.”

Napier 70-year-old Gayle Peters was told she was pre-diabetic about three years ago. With targeted diet advice, she reduced her sugar and carbohydrate intake and has not progressed to diabetes. PHOTO: SUPPLIED

WHERE’S THE HARM?

Gayle Peters was diagnosed with pre-diabetes about three years ago, after having an Hba1c test as part of continuing check-ups for an autoimmune condition.

The 70-year-old never considered herself at risk of diabetes. Part-Maori, but raised as a Pakeha, she grew up with good, wholesome food and was a keen walker, roaming Napier with her huskies.

“I thought I was far too active for that.”

She doesn’t recall her Hba1c level, but remembers being told she had “pre-something”.

“I figured if it was pre-whatever, then OK, you can change it.”

She knew diabetics, who needed insulin injections, and her fear of needles was motivation enough to change. She was referred to the Otago University pilot Pre-diabetes Intervention Programme in Primary Care (Pipi), trialling targeted diet advice through GP practice nurses. 

She kept a food diary of what – and how much – she ate and was surprised to discover sugar lurking in seemingly healthy foods.

“I love my fruit – that was my biggest downfall.”

She now eats fewer strawberries and greener fruit. She’s swapped white rice for couscous or mixed rice, eats more fish and only fibre-dense bread. When family visit, it’s a big feed, but a healthy one. 

“They know what I’m doing and that I won’t allow them to have rubbish. Not here.” 

She’s lost some weight, and has not progressed to full diabetes. Overall, she found the experience “very useful”.

“It was a bit stressful – because I didn’t quite know what I was in for. As you do it more and it starts becoming more second nature, it’s just changing your style of living.”

The main treatment for pre-diabetes is diet and lifestyle advice. PHOTO: WARWICK SMITH/FAIRFAX NZ

Researcher Sally Abel interviewed 20 of the 67 participants on the Pipi trial, which is now being rolled out more widely. After six months, four had returned to normal Hba1c levels, two had progressed to diabetes and 14 were still pre-diabetic, although some had lower Hba1c levels. Most were shocked by the pre-diabetes diagnosis, Abel says.

“It was like a wake-up call, and as a result of that, they felt quite motivated to do something about it … The other thing they found useful was having regular contact with a health professional that they felt accountable to.”

And that’s the tricky bit – experts report it’s precisely the fear factor of the pre-diabetes diagnosis that’s sometimes required to kickstart action. And there’s a crucial difference between Hba1c screening and prostate cancer screening – which can lead to invasive treatments with life-altering complications such as incontinence and impotence.

For pre-diabetes, the most common “treatment” is diet and lifestyle advice that would improve anyone’s health. There is a diabetes drug – metformin – but it’s less effective than weight loss and lifestyle change.

Otago University diabetes researcher Kirsten Coppell, who led the Pipi research, says a pre-diabetic Hba1c test needs to be weighed against other risk factors, such as ethnicity and family history. But she’s a vehement proponent of using a pre-diabetes diagnosis to spark change.

Her expanded study will look at socioeconomic, cultural factors and biochemistry, in the hope of better understanding which pre-diabetics will progress to diabetes, and who won’t.

“I think it’s our best measure at this point in time, of individual risk and – at an individual level – of being able to do something to prevent the progression and enable someone to go back to normal. I don’t think we should stop doing it. At all.”

College of GPs president Tim Malloy argues early targeting of at-risk patients could help stem the growing diabetes epidemic.

SO WHAT SHOULD WE DO ABOUT IT?

College of GPs president Tim Malloy doesn’t use the pre-diabetes label, and doesn’t think it’s routinely used by family doctors. Instead, he assesses diabetes risk based on family history, lifestyle, weight and blood glucose levels.

However, he supports identifying high-risk people and intervening early. Because the cost of diabetes is enormous, both to individuals and the health system.

“Uncontrolled diabetes has an end point which equals renal failure, limb amputation and blindness … That’s what we should be afraid of.”

At his practice alone, he has 40 diabetic patients who will need dialysis in 5 to 10 years.

“If we focus attention and resources entirely on them, we’re not going to change that outcome. They’re still going to end up on dialysis. We might delay it, but if we spend time and energy and effort both with them and with people so they don’t get to that point where their renal function is seriously compromised, then maybe we’ll pre-empt the numbers actually going on to dialysis.”

And then there’s the environment. The 2014 BMJ paper recommended shifting attention from “turning healthy people into patients with pre-diabetes” to changing the food, education and health policies driving the obesity epidemic.

Anti-junk-food campaigner Gareth Morgan was told he was pre-diabetic about four years ago. His conscious reform effort “lasted five minutes” but a family health kick has helped return his blood sugar to normal levels. PHOTO: KEVIN STENT/FAIRFAX NZ

Gareth Morgan – a member of Lancet medical journal’s Commission on Obesity – advocates corrective food taxes. Every food would be assigned a red, orange or green traffic light according to its nutritional value. Red foods would be taxed, with the money used to make green foods cheaper.

Looking back, Morgan thinks his pre-diabetes diagnosis was a useful wake-up call. When diagnosed, his Hba1c level was in the mid-range of pre-diabetes, at 44. Now, at 31, it’s normal. It wasn’t due to his conscious reform effort, which “lasted five minutes”. Instead, he’s been caught up in a family health-kick.

Malloy argues you need both individual interventions, and better public health policies. But what individual interventions? If 25 per cent of the population have pre-diabetes, we can’t afford to offer everyone intensive diet or exercise programmes, at a cost of up to $2000 per patient.

“It has to be something doable, cheap, that can be rolled out on a mass basis and isn’t going to bankrupt the country,” says endocrinologist and Otago University associate professor Jeremy Krebs.

He has just received $1.8 million to study whether a Fonterra-made probiotic can reduce obesity by changing the bacteria in the gut. Previous research has showed the gut microbiome of obese people differs from that of lean people. What’s not clear, is whether losing weight changes the gut bacteria, or whether lean gut bacteria can trigger weight loss.

Krebs also acknowledges Hba1c screening is far from perfect. Experts agree someone with an Hba1c of 45-50 has a high risk of progressing to diabetes and should be offered some intervention. But the bulk of those in the pre-diabetes range sit at the “much more controversial” 41-45 end. To label someone with pre-diabetes and offer no treatment is unethical, Krebs says. So the answer might be a two-tier system, with intensive green prescriptions for those at the top end, and basic lifestyle advice for those at the bottom.

“If you were a European person, with no family history of diabetes, normal blood pressure, normal cholesterol levels and your weight was normal or only just slightly up, and your Hba1c was 41, then actually you probably don’t need anything at all. You’re pretty healthy really. Whereas if you’re Maori and you have hypertension and five family members have dialysis because of their diabetes, then actually it’s much more relevant.”

MORE * If you live in the greater Wellington area, have been diagnosed with pre-diabetes and want to volunteer for Jeremy Krebs’s study investigating whether probiotics could help reduce sugar and fat levels, email prediabetes.study@otago.ac.nz

THE OVERDIAGNOSIS DEBATE

As Auckland GP John Cameron once put it, “We’ve all got what is called pre-death. It’s the disease you get before you die and we’re all suffering from it.”

Growing recognition that more medicine is not necessarily good medicine has spurred the international Choosing Wisely movement.

Its New Zealand chairman, Nelson ophthalmologist Derek Sherwood, says the growth in screening, testing and treatment has been partly driven by better technology picking up previously undiscovered (and benign) abnormalities; doctors worrying about “errors of omission” and patients googling their symptoms and turning up to family doctors with a list of the investigations they require.

“I think there’s a belief out there in the community, that more is better – that early diagnosis is a good thing. So therefore, what harm is there in doing a test? That has to be a good thing. And I think there’s a slightly optimistic belief in modern medicine being able to fix things …

“In the past 20 or 30 years, we’ve moved from treating diseases to treating risk factors.”

The website gives information about common overdiagnosis or overtreatment areas, such as lower back pain and antibiotic use.

Sherwood says Kiwi patients also need better decision-making tools, such as an app being developed for controversial prostate cancer testing, which would require patients to answer a questionnaire about the risks and benefits, before being able to fill out a lab test request form.

“I think we just have to get people asking their doctor more often: ‘Do I really need to have this? What would happen if I didn’t?’ “

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