And research suggests the risk remains high, even if blood glucose levels are later brought under control.
There’s no doubt type 2 diabetes raises the risk of cardiovascular events.
But new research presented at the American College of Cardiology’s 70th Annual Scientific Session has shown people with intermediate hyperglycaemia also experience a significantly increased risk of heart attack, stroke or other major cardiovascular event, when compared to people with normal blood sugar levels.
The retrospective study reveals that serious cardiovascular events occurred in 18% of people with intermediate hyperglycaemia compared with 11% of people with normal blood glucose levels over a median of five years’ follow-up.
The relationship between higher blood glucose levels and cardiovascular events remained significant even after taking into account other possible compounding factors, such as age, gender, body mass index, blood pressure, cholesterol and smoking.
The chances of having an event in people with intermediate hyperglycaemia was also highest in certain groups, including males, people with a family history of cardiovascular disease and those with personal risk factors for heart disease.
Weight also played a role; people who were overweight had the highest rates of cardiovascular events among all patients, even more than those who were obese.
Lead author Dr Adrian Michel, an internal medicine resident at Beaumont Hospital-Royal Oak in Michigan, believes instead of focusing on preventing diabetes alone, clinicians should shift focus to preventing intermediate hyperglycaemia.
‘In general, we tend to treat intermediate hyperglycaemia as no big deal,’ he said.
‘But we found that intermediate hyperglycaemia itself can significantly boost someone’s chance of having a major cardiovascular event, even if they never progress to having diabetes.’
Because the research found that having intermediate hyperglycaemia ‘nearly doubled’ the chance of a major adverse cardiovascular event, Dr Michel says prevention of this state needs to be taken more seriously.
‘As clinicians, we need to spend more time educating our patients about the risk of elevated blood sugar levels and what it means for their heart health, and consider starting medication much earlier or more aggressively, and advising on risk factor modification, including advice on exercise and adopting a healthy diet,’ he said.
Dr Gary Deed, Chair of RACGP Specific Interests Diabetes, told newsGP there is debate over the classification of elevated blood glucose levels both in Australia and internationally, and what to call these states.
He says some organisations use the term ‘intermediate hyperglycaemia’ while others prefer ‘prediabetes’, and that definitions of glucose cut-offs vary internationally.
According to the RACGP’s National guide to a preventive health assessment for Aboriginal and Torres Strait Islander people, intermediate hyperglycaemia is defined according to the results of a two-hour oral glucose tolerance test (OGTT).
Impaired fasting glucose is defined as a fasting glucose between 6.1–6.9 mmol/L and a two-hour glucose <7.8 mmol/L.
Meanwhile, impaired glucose tolerance is defined as a fasting glucose < 7 mmol/L and two-hour glucose ≥7.8 mmol/L and ≤11 mmol/L.
Regardless of what it is called, Dr Deed says intermediate hyperglycaemia ‘is not a benign state’, and cited a meta-analysis published in the British Medical Journal in May 2020, which accounted for ‘all the different definitions’ of intermediate hyperglycaemia.
For that research, a total of 129 studies were included, involving more than 10,000,000 individuals for analysis.
It found that, in the general population, intermediate hyperglycaemia was associated with an increased risk of all cause mortality, composite cardiovascular disease, coronary heart disease and stroke.
Dr Deed says this new research builds on that previous paper, and adds further weight to calls for addressing a state of increased glycaemia, before it reaches the definition of diabetes, as there is a ‘clustering of risk’ for cardiovascular disease that occurs in patients.
‘There’s elevated weight, also elevated blood pressure and cardiovascular risks, and adding glycemic elevations obviously amplifies background risks as well,’ he said.
‘These are patients that should be identified. I don’t necessarily mean that we aggressively treat the glycaemia using medications, but you’re trying to address all the modifiable risk factors – weight, blood pressure, physical activity – as important interventions.’
The authors also warn that simply addressing raised glucose levels may not reduce the cardiovascular risk associated with intermediate hyperglycaemia.
They were concerned to discover that if a person with intermediate hyperglycaemia was able to bring their blood glucose levels back to the normal range, their risk of having a cardiovascular event remained high.
Events occurred in more than 10.5% of these patients, compared with 6% of those with no diabetes or intermediate hyperglycaemia.
‘So preventing intermediate hyperglycaemia from the start may be the best approach,’ Dr Michel said.
Dr Deed agrees with that approach.
However, he says that patients with intermediate hyperglycaemia should still be encouraged to reduce their glucose levels.
‘Normalisation of the glucose in a person with intermediate hyperglycaemia gives them the best chance of stopping them developing type 2 diabetes,’ he said.
‘But addressing all those modifiable risk factors will also somewhat reduce their risk of cardiovascular disease.’
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cardiovascular disease diabetes glucose levels intermediate hyperglycaemia stroke