- Large Danish study linked national health records with detailed reviews of sudden deaths
- People with type 1 diabetes had nearly four times the rate of sudden cardiac death
- People with type 2 diabetes had more than six times the rate of sudden cardiac death
A nationwide study from Denmark has put hard numbers on a fear that many clinicians already suspected.
Sudden cardiac death is much more common in people with type 1 and type 2 diabetes than in the general population, and it accounts for a significant share of the years of life lost.
The research, published in the European Heart Journal, followed the entire Danish population throughout 2010.
The authors used multiple national registers to identify people with diabetes, classify deaths and estimate how many life years were lost because of sudden cardiac death.
What the researchers did
The team started with all 5.5 million people living in Denmark at the start of 2010. Over that year, just over 54,000 people died.
For each death they gathered information from death certificates, hospital discharge records and, where available, post mortem reports.
Two physicians independently reviewed every potential sudden death. They discussed disagreements until they reached a consensus and one doctor checked all cases to rule out deaths that were clearly not sudden or were due to accidents or other non natural causes.
People with diabetes were identified using diagnosis codes in the national patient register and records of prescriptions.
The method used to define type 1 diabetes had very high specificity, meaning there were few false positives, although some cases may have been missed.
The method used for type 2 diabetes captured the vast majority of cases.
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The numbers behind the risk
Among people with type 1 diabetes, there were 97 sudden cardiac deaths during the year.
Among those with type 2 diabetes there were 1,149 sudden cardiac deaths.
When the researchers calculated incidence rates per 100,000 person years, the differences were stark.
In the general population the rate of sudden cardiac death was 105 per 100,000 person years. For people with type 1 diabetes it was 394, and for those with type 2 diabetes it was 681.
The relative risk was particularly high in younger adults.
In some age bands, people in their thirties with type 1 diabetes were more than twenty times as likely to die from sudden cardiac causes as their peers without diabetes.
The relative risk narrowed with age, partly because sudden cardiac death becomes more common in the wider population as people get older.
Life expectancy lost
The authors then looked at life expectancy. For a thirty year old without diabetes, they estimated the expected remaining years of life.
They compared this with estimates for thirty year olds with type 1 or type 2 diabetes, breaking down the years of life lost by cause of death.
A person aged thirty with type 1 diabetes was expected to live about 14 years fewer than someone of the same age without diabetes.
Of those lost years, 3.4 were due specifically to sudden cardiac death.
For a thirty year old with type 2 diabetes, expected life span was almost eight years shorter, with 2.7 of those years lost to sudden cardiac death.
These figures underline that sudden cardiac death is not a rare outlier but a major contributor to the reduced life expectancy associated with diabetes.
Why the risk is higher
The study confirms that people with diabetes who suffer sudden cardiac death tend to have more heart related and non heart related illnesses than those without diabetes.
Conditions such as ischaemic heart disease, heart failure and arrhythmias were more common, as were kidney and nerve problems.
Many of the people who died suddenly had previous hospital admissions for diabetes related problems, including severe hypoglycaemia.
The findings raise concern that repeated low blood sugar episodes may contribute to the risk of sudden death, although the study cannot prove cause and effect.
Even after the researchers adjusted for other illnesses, diabetes itself remained an independent risk factor for sudden cardiac death.
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What people with diabetes can do
These findings are sobering, not least because sudden cardiac death often affects people with no obvious warning signs.
However, they also reinforce messages that can reduce risk.
Good long term glucose control, blood pressure management and careful lipid control are all known to reduce cardiovascular complications.
Avoiding smoking, staying active, taking prescribed medicines reliably and attending regular reviews remain critical.
Anyone with diabetes who experiences chest pain, unexplained shortness of breath, palpitations or episodes of fainting should seek urgent medical attention.
People who have had severe hypos, particularly if they live alone, should discuss this with their diabetes team so that treatment and monitoring can be adjusted.
