Researchers at the University of Leeds tracked 700,000 people who had been admitted to hospital with a heart attack between January 2003 and June 2013.
Of these, 121,000 had diabetes.
After stripping out the effects of age, sex, any other illnesses and differences in the emergency medical treatment received, the team found stark differences in survival rates.
People with diabetes were 56 per cent more likely to have died if they had experienced a ST elevation myocardial infarction (STEMI) heart attack – in which the coronary artery is completely blocked – than those without the condition.
They were 39 per cent more likely to have died if they had a non-ST elevation myocardial infarction (NSTEMI) heart attack – in which the artery is partially blocked - than those without diabetes.
Lead researcher Dr Chris Gale, Consultant Cardiologist and Associate Professor in the university’s School of Medicine, said: “These results provide robust evidence that diabetes is a significant long-term population burden among patients who have had a heart attack.
“Although these days people are more likely than ever to survive a heart attack, we need to place greater focus on the long-term effects of diabetes in heart attack survivors.
“The partnership between cardiologists, GPs and diabetologists needs to be strengthened and we need to make sure we are using established medications as effectively as possible among high-risk individuals.”
He added that the next step in their research would be finding out exactly what it is about having diabetes that increases the risk of death following heart attack.
Dr Mike Knapton, Associate Medical Director at the British Heart Foundation, which funded the study said: “We knew that following a heart attack, you are less likely to survive if you also have diabetes.
“However, we did not know if this observation was due to having diabetes or having other conditions which are commonly seen in people with diabetes.
“This paper is the first to conclusively show that the adverse effect on survival is linked to having diabetes, rather than other conditions people with diabetes may suffer from.
“This research highlights the need to find new ways to prevent coronary heart disease in people with diabetes and develop new treatments to improve survival after a heart attack.
“The British Heart Foundation is committed to funding research in this area.
“We are currently funding researchers in Leeds to find new ways of keeping blood vessels healthy in people with diabetes in the fight for every heartbeat.”
Dr Anna Morris, Head of Research Funding at Diabetes UK, said: “While researchers tackle this issue, we know that managing diabetes effectively can reduce the risk of developing cardiovascular disease.
“This includes eating healthily, keeping active and taking medications as prescribed by your doctor.
“It’s essential that people with diabetes get the support they need to do this effectively, and that we continue to fund research across the UK aimed at preventing the onset of complications in the first place.”
Source: University of Leeds
The study is published in the Journal of Epidemiology and Community Health.