Researchers studied the autopsies of 868 people in the county who had sudden deaths and found 151 people were homeless.
They found the people who had experienced homelessness were more likely to be male and generally younger at the age of 56 years of age compared to 61 for the general population.
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There was also a higher prevalence of alcohol and substance use and mental health issues among the homeless population.
Researchers found that homeless individuals died most often from noncardiac causes, including drug overdoses, gastrointestinal disorders and infections, while people who died more frequently from arrhythmic causes.
“While the high rate of substance use in the homeless population has long been recognised, our study demonstrates its association with early, sudden mortality and its true impact among homeless people,” said UCSF cardiology fellow and author Leila Haghighat.
“By contrast, housed individuals more closely reflected the classic profile of sudden death that modern medical systems aim to resuscitate and prevent.”
The study showed the need for public defibrillators as well as the need to “redouble efforts” to treat substance abuse and provide targeted immunisation to vulnerable people, Haghighat added.
Homeless deaths have been given greater attention in the UK following the Dying Homeless project, which saw the Bureau of Investigative Journalism start counting homeless deaths in 2017.
The project is still running and is now helmed by the Museum of Homelessness. The most recent UK-wide statistics were released in April and revealed 1,313 people died while rough sleeping or in emergency or insecure housing in 2022.
There are now official counts for England, Wales and Scotland too. These counts use a different methodology to the Dying Homeless project – analysing death certificates and using modelling rather than freedom of information requests to local authorities.
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The most recent Office for National Statistics count found an estimated 741 deaths of people experiencing homelessness were registered in 2021 across England and Wales.
Most people who died were male, like in the US study, but the ONS found people in the UK died at a younger age when experiencing homelessness. On average, men died at the age of 45 while women died at just 43 years old.
As for Scotland, the National Records of Scotland estimated 250 people died while homeless in 2021 with similar demographics to the rest of the UK.
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