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Sudden deaths are often assumed to be caused by a failing heart. But about 17 per cent of deaths assumed to be caused by cardiac arrest may actually have resulted from drug overdose, according to a study in San Francisco.
Many of the deaths were linked to the use of opioid drugs. “It indicates that the ‘dark number’ of opioid overdoses may be a lot higher than what we assumed,” says Rebecca McDonald at King’s College London, who wasn’t involved in the research.
Between 2011 and 2017, Zian Tseng at the University of California, San Francisco, and his colleagues performed autopsies on 767 people who had died suddenly in the city. All of the individuals were presumed by emergency medical staff to have died from cardiac arrest, which occurs when the heart stops beating properly, and blood is unable to effectively pump around the body.
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Such cases wouldn’t normally undergo an autopsy, but post-mortem toxicology tests revealed that 17 per cent of these individuals actually died from a drug overdose. This was despite the fact that “paramedics had called these cardiac arrests and the [medical examiner] had discovered no evidence of drugs at the scene, and had no suspicion of drug overdose”, says Tseng.
Most of these people were found to have been taking a cocktail of drugs, but the most commonly found drugs were opioids. Just over two-thirds of those found to have died from drug overdose appear to have been taking opioids – and almost half of those individuals had been taking those drugs on prescription.
Opioid drugs – which include codeine, morphine and fentanyl – are typically prescribed to treat pain, but it is easy to become dependent on them. People that do develop dependence are at risk of seeking out higher doses and illicit opioids, including heroin. Opioids were involved in 46,802 overdose deaths in the US in 2018, according to the US Centers for Disease Control and Prevention (CDC). But this figure may be an underestimate, say Tseng and his colleagues.
The finding could have implications for the treatment of suspected cardiac arrest. The effects of an opioid overdose can be halted using a drug called naloxone, which is thought to be safe to use even in individuals who haven’t taken opioids. “The question is… should naloxone be given in other cases where opioid overdose cannot be ruled out?” asks McDonald.
Tseng thinks so. “Naloxone is an inexpensive, low-risk intervention that could potentially save many lives if incorporated into resuscitation strategies by paramedics for presumed cardiac arrests, either targeted or universally,” he says.
It isn’t clear if the finding will apply to other parts of the US or other countries. “I don’t know how easily it can be extrapolated, because the system of death reporting is so different in different parts of the country,” says Joshua Sharfstein at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland. “There’s no one national standard for what gets declared an overdose, and how it is declared.”
The finding also questions the accuracy of other health statistics, says Tseng. “Without post-mortem confirmation, all causes of death on death certificates are just educated guesses,” he says. “Therefore, all aggregate mortality data reported by the CDC [and other health organisations] on cancer mortality, heart disease mortality, etc. should be taken with a grain of salt.”
Journal reference: Annals of Internal Medicine, DOI: 10.7326/M20-0977
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