Thousands of unexplained extra deaths are happening per week during the Covid-19 outbreak. Why?

The question that is preoccupying statisticians and epidemiologists.

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Every week as the coronavirus outbreak continues, hundreds, and now thousands, more people are dying than we would normally expect in normal times. The death rate in the UK is now at its highest for more than 20 years, 75 per cent above the five-year average, according to the Office of National Statistics. 

But crucially, and fascinatingly to the scientific community, not all of these extra deaths are attributed to Covid-19. Of the nearly 8,000 extra deaths that took place in England and Wales in the week ending 10 April, only 6,200 were directly attributed to coronavirus, leaving nearly 2,000 extra, unexplained deaths. 

“The disparity was even larger last week,” emphasises Dr Jason Oke, senior statistician in the Oxford University Medical Statistics Group. “In the week ending 3 April, there were 6,000 excess deaths, and 3,000 to 4,000 were unexplained. That was particularly surprising.”

As the graphic below illustrates, deaths in the UK have happened at slightly above the seasonal average since January, but in the recent weeks of the Covid-19 outbreak the number of unexplained excess deaths has risen to above a level that can be explained by natural fluctuations week by week. “That 2,000 can’t be explained by random variation,” Dr Oke confirms. “It’s larger than that, so there’s definitely something.” 

Graph by Nicu Calcea

There’s definitely something, but the “death gap” leaves medics and statisticians in the strange situation of being unable to explain further, beyond a reasonable certainty that there are two possible explanations. Dr Oke said: “There’s not enough information to know whether this is under-reporting of Covid or whether this is, not a term I particularly like, but one that has been bandied around, 'collateral damage' as a result of the lockdown.” 

Both explanations point towards an alarming trend. The first suggests an under-reporting of coronavirus deaths despite the ONS’s efforts to ensure the fullest picture of potential Covid deaths. The ONS figures referred to in this article and by Dr Oke take into account all registered deaths, not simply those registered in hospitals, and include any death where Covid-19 is mentioned on the death certificate  even if not mentioned as the primary cause. This means any potential difficulty in determining whether Covid-19 was a cause of death to a particularly ill patient with multiple comorbidities does not apply: any death “with” Covid-19 is counted by the ONS under “deaths involving Covid-19”. 

Furthermore, ONS guidelines are clear that “a doctor can certify the involvement of Covid-19 based on symptoms and clinical findings – a positive test result is not required”. Noting that the “death gap” has narrowed since the week ending 3 April, Dr Oke suggested that doctors may be more willing to certify Covid-19 without a test than they were in earlier weeks, reducing the number of unexplained excess deaths.

The other possible explanation is that these figures do indeed point to an increase in deaths by non-coronavirus causes, an early indication of the potentially devastating impact that the pandemic response has had on wider healthcare provision, from a 50 per cent drop in A&E attendance to “eerily quiet” wards, as reported in an in-depth study on the time-bomb of patients avoiding hospital

“It’s going to be one of those two causes,” Dr Oke said, adding: “It's something that everybody who’s interested in epidemiology and statistics is paying great attention to, but unfortunately at the moment we can’t get any deeper into it.”

The ONS has said it will conduct further investigation of excess deaths not involving Covid-19.  But on Tuesday, the organisation’s head of health analysis, Nick Stripe, said that establishing the exact reasons could take months  or even years.

Ailbhe Rea is political correspondent at the New Statesman

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