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Prediabetes and Heart Disease: Why Your Heart Is at Risk Before Diabetes

A BMJ review of 10 million people linked prediabetes to higher risk of heart disease, stroke and death. Dr. Sayantan Banerjee explains why, which checks to ask for, and how to lower risk.

PREDIABETES REMISSION

Dr. Sayantan Banerjee

10/31/20268 min read

Most people think of prediabetes as a warning about diabetes, and it is. But it is also a warning about the heart. Long before glucose reaches the diabetes range, the same underlying problems, insulin resistance, excess fat around the organs, raised blood pressure and unhealthy cholesterol patterns, are already affecting the blood vessels.

This article explains what the research shows about prediabetes and heart disease, why the two are linked, which checks you should ask for, and the steps that lower your risk.

What the evidence shows

The largest summary of the evidence was published in The BMJ in 2020. Researchers combined results from 129 studies involving more than 10 million people. In the general population, followed for a median of nearly 10 years, people with prediabetes had a higher risk than people with normal glucose of:

death from any cause, about 13% higher
cardiovascular disease overall, about 15% higher
coronary heart disease, about 16% higher
stroke, about 14% higher

These increases are modest in relative terms. In absolute terms, the extra risk was around 7 to 9 additional cases per 10,000 people per year for death and cardiovascular disease. Across millions of people with prediabetes in the US and UK, that adds up to a large number of heart attacks and strokes.

The risk was higher in people who already had heart disease. In that group, prediabetes was linked with about a 36% higher risk of death and a 37% higher risk of further cardiovascular events over a shorter follow-up.

The review also found that impaired glucose tolerance, meaning high glucose two hours after a glucose drink, carried more risk than impaired fasting glucose. This fits with other research suggesting that large glucose spikes after meals may be particularly harmful to blood vessels.

Why prediabetes affects the heart

Several processes link the two.

Insulin resistance. The same insulin resistance that drives up glucose also affects how blood vessels work. It is linked with stiffer arteries, reduced ability of vessels to relax, and a tendency for blood to clot more easily.

Blood pressure. Insulin resistance and excess visceral fat are linked with higher blood pressure. The kidneys hold on to more salt, and the nervous system that controls blood vessels becomes more active.

Cholesterol and triglycerides. Insulin resistance typically produces a pattern of high triglycerides, low HDL cholesterol, and smaller, denser LDL particles, which are thought to be more harmful to arteries. This pattern can be present even when total cholesterol looks normal.

Inflammation. Visceral fat releases inflammatory signals into the blood, which contribute to the build-up of fatty plaques in artery walls.

Glucose spikes. Repeated spikes in glucose after meals may damage the lining of blood vessels.

Fatty liver. Fatty liver, which is common in prediabetes, is itself linked with higher cardiovascular risk.

These changes tend to travel together. When three or more are present, such as a large waist, high blood pressure, high triglycerides, low HDL and raised glucose, doctors call it metabolic syndrome, which roughly doubles the risk of heart disease.

Your risk is the sum of all your factors

Prediabetes on its own raises risk a little. Combined with other risk factors, it raises it a lot more. The biggest contributors to heart disease and stroke are:

smoking
high blood pressure
high LDL cholesterol
diabetes and prediabetes
excess weight, especially around the waist
physical inactivity
family history of early heart disease
age and sex
chronic kidney disease

That is why your doctor will look at your overall risk, not just your glucose.

Checks to ask for

If you have prediabetes, ask your doctor about:

Blood pressure. Ideally checked more than once, or at home. In the US, the American College of Cardiology and American Heart Association guideline defines high blood pressure as 130/80 mmHg or above. In the UK, NICE uses 140/90 mmHg in clinic, or 135/85 mmHg on home readings, to diagnose hypertension.

A full cholesterol profile. This should include LDL, HDL, triglycerides and non-HDL cholesterol.

A cardiovascular risk score. In the UK, the QRISK3 calculator estimates your 10-year risk of heart attack or stroke. NICE suggests offering a statin to people with a 10-year risk of 10% or more, after discussing the options. In the US, doctors use calculators such as the AHA PREVENT equations or the older pooled cohort equations to guide decisions about statins and other treatments.

Kidney tests. A blood test for kidney function and a urine test for albumin.

Waist measurement. A waist more than half your height signals extra visceral fat.

Liver tests, if fatty liver is suspected.

In England, the NHS Health Check, offered to adults aged 40 to 74 every five years, includes many of these checks.

Does treating prediabetes protect the heart?

The evidence here is encouraging but less clear-cut than for diabetes prevention.

In China, the Da Qing study ran a six-year lifestyle programme for people with impaired glucose tolerance in the 1980s. After 30 years of follow-up, people in the lifestyle groups had fewer cardiovascular events and lower death rates than the control group, as well as a delay in developing diabetes.

In the US Diabetes Prevention Program, lifestyle change and metformin both reduced diabetes, and lifestyle change improved blood pressure, cholesterol and other risk factors. But long-term follow-up hasn't shown a clear reduction in heart attacks and strokes so far, possibly because participants also received good general care and many in all groups began taking blood pressure and cholesterol medicines over time.

What is clear is that the individual risk factors that travel with prediabetes, high blood pressure, high LDL cholesterol, smoking and inactivity, are strongly linked to heart disease, and treating them reduces risk. So a sensible approach is to treat prediabetes and its companions together.

What lowers your risk

Stop smoking. This is the single most effective step if you smoke. Risk falls quickly after stopping. The NHS Stop Smoking Services and US quitlines (1-800-QUIT-NOW) offer free support.

Move every day. Regular activity lowers blood pressure, improves cholesterol and insulin sensitivity, and reduces visceral fat. Aim for at least 150 minutes a week of moderate activity, plus strength exercise twice a week. Walking after meals helps glucose spikes in particular.

Lose some weight if you need to. Losing 5% to 10% of body weight improves blood pressure, triglycerides, HDL and glucose.

Eat for your heart and your glucose. A Mediterranean-style pattern, built around vegetables, fruit, legumes, whole grains, nuts, olive oil and fish, with less red and processed meat, fewer sugary drinks and fewer ultra-processed foods, supports both. In the PREDIMED trial in Spain, a Mediterranean diet with extra virgin olive oil or nuts reduced major cardiovascular events in people at high risk.

Reduce salt. Most adults eat more than the recommended limit of about 6 g of salt a day in the UK, or 2,300 mg of sodium a day in the US. Much of it comes from bread, processed meats, ready meals and takeaways.

Keep alcohol moderate. Within UK guidance of 14 units a week, or less.

Sleep well. Short sleep and untreated sleep apnoea are linked with high blood pressure and heart disease.

Take medicines if they are recommended. If your blood pressure or cholesterol is high, or your overall risk is high, medicines such as statins and blood pressure tablets substantially reduce the risk of heart attack and stroke. They work alongside lifestyle changes, not instead of them.

Know the warning signs

Prediabetes itself causes no symptoms, but heart attacks and strokes do. Call 999 in the UK or 911 in the US if you or someone else has:

chest pain or pressure, which may spread to the arm, neck, jaw or back
sudden shortness of breath
sudden weakness or numbness of the face, arm or leg, especially on one side
difficulty speaking or understanding speech
sudden loss of vision or severe headache

The UK FAST campaign (Face, Arms, Speech, Time) and the US BE FAST campaign help people recognise stroke symptoms.

A heart-protection plan for prediabetes

Know your numbers: A1C, blood pressure, cholesterol, waist and kidney function.
Ask for your 10-year cardiovascular risk score.
If you smoke, set a quit date and get support.
Walk daily, especially after meals, and add strength exercise twice a week.
Shift your diet towards a Mediterranean-style pattern and cut sugary drinks.
Aim for a 5% to 10% weight loss if you have overweight.
Discuss statins or blood pressure treatment with your doctor if your risk is raised.
Recheck everything at least once a year.

Women, prediabetes and heart disease

Heart disease is a leading cause of death in women in both the US and UK, yet women's risk is often underestimated. Prediabetes and diabetes appear to raise cardiovascular risk at least as much in women as in men, and in some studies more.

Several factors are specific to women. A history of gestational diabetes is linked to a higher risk of both type 2 diabetes and heart disease later in life. Pre-eclampsia and high blood pressure in pregnancy also raise long-term cardiovascular risk. PCOS is linked with insulin resistance and an adverse cholesterol pattern. And after menopause, falling oestrogen is associated with more abdominal fat, rising LDL cholesterol and higher blood pressure.

If you are a woman with prediabetes and any of these in your history, make sure your doctor knows, and ask for a full cardiovascular risk assessment.

The kidney connection

The kidneys, heart and metabolism are closely linked. Prediabetes and high blood pressure can both affect the small blood vessels in the kidneys, sometimes showing up as small amounts of albumin, a protein, in the urine. Albumin in the urine is itself a marker of higher cardiovascular risk.

A simple urine test, often called an albumin-to-creatinine ratio, along with a blood test for kidney function, can pick up early changes. If kidney changes are found, treating blood pressure and glucose carefully, and sometimes using specific medicines that protect the kidneys and heart, can slow progression.

Small numbers, big changes

It is easy to feel that a 5% fall in weight or a 5 mmHg drop in blood pressure won't make much difference. But at the level of the heart and blood vessels, these changes add up. Lower blood pressure, better cholesterol, lower glucose and less visceral fat each reduce risk, and together they can reduce it substantially. The same habits that reverse prediabetes protect the heart.

How my book can help

The Prediabetes Exit Strategy explains how insulin resistance affects the whole body, not just glucose, and sets out practical changes to eating, movement, sleep and daily routine that support both metabolic and heart health. It is designed to help you have a better conversation with your doctor. More on the book page.

Frequently asked questions

Does prediabetes cause heart disease? It is linked with a modestly higher risk of heart disease and stroke, largely through insulin resistance, blood pressure and cholesterol changes.

Can prediabetes damage your heart before diabetes develops? Yes. Changes in blood vessels, blood pressure and cholesterol can begin during prediabetes.

Should I take a statin if I have prediabetes? It depends on your overall cardiovascular risk. Ask your doctor to calculate it.

Does reversing prediabetes lower heart risk? Improving glucose usually comes with better blood pressure, cholesterol and weight, which lowers risk. Long-term trial evidence for heart outcomes is still developing.

Which is more dangerous, high fasting glucose or high glucose after meals? In the 2020 BMJ review, impaired glucose tolerance, meaning high glucose after a glucose drink, carried more risk.

What blood pressure should I aim for? Your doctor will advise. In the US, below 130/80 mmHg is the general target for many adults. UK targets depend on age and other conditions.

Can young people with prediabetes have heart problems? The risk is lower in absolute terms for younger people, but early prediabetes is a sign that risk factors are starting to build. Acting early protects the heart for decades.

Does aspirin help? Aspirin isn't recommended for most people without existing heart disease, because the bleeding risk often outweighs the benefit. Ask your doctor before taking it.