Behind the daily death figures, there is a more complicated picture of the impact of Covid-19 in Australia that raises questions about whether Covid could be causing more deaths from ischaemic heart disease, cerebrovascular disease and dementia.
As cases exploded after the emergence of the Omicron variant, the number of Covid deaths similarly rose, with more than 80% of Australia’s total Covid deaths occurring in 2022.
There has also been an increase in the proportion of people who died with Covid as a contributing cause of death, rather than as the primary cause of death:
The difference between these groups is important – due to some previous misinterpretation of the figures – and so is the contribution of pre-existing chronic conditions.
The Australian Bureau of Statistics (ABS) tracks Covid mortality in a monthly report, and divides Covid deaths into “deaths due to Covid” and “Covid-related deaths”.
Deaths due to Covid accounts for the vast majority of deaths during the pandemic, and includes any death where Covid was considered to be the underlying cause of death. This includes deaths that had other associated conditions listed on the death certificate, such as pneumonia due to Covid or pre-existing chronic conditions.
Covid-related deaths includes deaths where the person either died with Covid, or had complications from a previous Covid infection but the virus was not the underlying cause of death. Importantly, the ABS said that while Covid did not directly cause the death of these people, it was still considered to have contributed to the death.
Prof Roger Byard, a forensic pathologist from the University of Adelaide, said it’s very difficult to know how much Covid contributed to death in these instances without knowing the full details of each case
“You’ve got the whole spectrum of Covid causing the disease [listed as the cause of death], Covid contributing to the disease, and Covid not being related to the disease, and there’s grey zones in all of those areas,” he said.
Gideon Meyerowitz-Katz, an epidemiologist at the University of Wollongong, said interpreting the increasing proportion of deaths with Covid was complicated.
“It is possible that the increasing number of deaths where Covid-19 is listed as a co-morbidity rather than a contributing factor to death is simply because the prevalence of Covid is so high, so there are more people who are already dying who are categorised as having Covid-19,” he said.
“It’s also possible that this indicates a reduction in the overall severity, perhaps due to vaccination, and that what’s happening is that Covid-19 is then less fatal than before.”
Another way to measure the impact of Covid is to look at excess deaths – that is, how the number of deaths in a given time period compares with how many deaths we might have expected in that time period based on a model using deaths from previous years without Covid.
In Australia, the Actuaries Institute has been estimating excess deaths using data published by the ABS. This chart shows their latest analysis on excess deaths throughout the pandemic:
Their analysis showed the deaths have been above the expected range for every week in 2022. As the ABS publishes the number of deaths due to Covid for each week, the Actuaries Institute has been able to estimate the contribution of Covid deaths to the overall number of excess deaths in their model, which they’ve put at 50%.
This suggests the pandemic may be having a broader impact on death numbers beyond the recorded deaths from Covid, or that something else is happening simultaneously to drive up death numbers.
In particular, the Actuaries Institute reports suggests deaths from ischaemic heart disease, cerebrovascular disease and dementia were all above the expected rates for 2022 so far:
The reason for the overall increase in excess deaths is not known, but several possibilities have been suggested. As reported by the Sydney Morning Herald, the chief medical officer, Paul Kelly, said at a conference in July that the increased deaths were in part due to the effectiveness of earlier pandemic measures.
“The people that haven’t died in the last two years because we had no flu because we did not have [high rates of] Covid and for various other reasons, are now, unfortunately, in that difficult position of being high risk despite the high vaccination rate, and that is by far the majority of people that are dying,” Kelly said.
Research published in Nature Medicine in February suggested people who have contracted Covid were at higher risk of cardiovascular disease post-Covid, including ischaemic heart disease and cerebrovascular disease.
Another suggestion for something that could be driving increased excess deaths was that people have delayed healthcare due to the pandemic. A review of research into healthcare utilisation during the pandemic confirmed some people avoided or delayed healthcare in various countries during 2020, but the paper suggested it is not clear that this would necessarily lead to adverse outcomes overall.
