Introduction
In Australia excess mortality or ‘excess
deaths’ are the difference between the number of deaths from all-causes compared
to the number of ‘expected’ deaths.
In 2022 there were an estimated 18,600 to 20,200 more deaths
(‘excess deaths’) than might have occurred in the absence of the COVID-19 pandemic.
More than half of these deaths were from COVID-19, but the greater than
expected number of deaths from cancer, dementia, diabetes, and heart disease
highlight some of the pressures the pandemic placed on our health and care
systems.
Preliminary mortality figures for the first few months in
2023 show Australia is still experiencing excess deaths. Monitoring the gap
between expected and actual deaths can provide early indications of the people and
institutions most at risk in an emergency (such as the COVID-19 pandemic) and support
better targeting of interventions and resources.
What is excess
mortality?
In Australia, reported excess mortality is the deaths from
all diagnosed causes (including COVID-19) which are greater than might be expected
when compared with a modelled estimate based on recent historical experience.
The World
Health Organization (WHO) defines excess deaths as:
Excess mortality is defined as the
difference between the total number of deaths estimated for a specific place
and given time period and the number that would have been expected in the
absence of a crisis (e.g., COVID-19 pandemic). This difference is assumed to
include deaths attributable directly to COVID‑19 as well as deaths
indirectly associated with COVID-19 through impacts on health systems and
society, minus any deaths that would have occurred under normal circumstances
but were averted due to pandemic-related changes in social conditions and
personal behaviours.
Why track
excess mortality?
Excess mortality can show the extent an event (such as a
pandemic or a natural disaster) is affecting the population.
Australia’s health and vital statistics systems allow
accurate and relatively timely reporting of COVID-19 cases and deaths. During
the early days of the pandemic, there were few (if any) deaths from COVID-19 in
Australia where COVID-19 was not recorded on the death certificate. This is not
the case for all countries monitored by the WHO,[1]
where excess deaths may be a proxy for COVID-19 deaths due to insufficient
COVID-19 testing and/or diagnosis guidelines.
Analysing the difference between actual and expected deaths
can offer early indications of:
-
the health risks and social effects of having high numbers of infectious
diseases circulating, and
-
areas where health systems may be under additional short or
long-term stress, with potential flow on effects on the health of the
population and the ability of our health systems to respond to changing health
needs.
The WHO
(2022) Q&A on Global excess deaths associated with the COVID-19 pandemic
notes:
Deaths directly attributable to COVID-19
provide only a narrow perspective of the wide ranging harms being caused by the
pandemic. The collateral damage from COVID-19 is much wider. It is important to
quantify this now as it can inform choices that governments must make regarding
prioritization between routine and emergency health systems.
The WHO also note that ‘excess mortality estimates go
beyond estimation of the impact of the COVID-19 pandemic’ and support
decision makers in ‘better targeting of interventions and resources to those
most in need to prevent future deaths’ and in preparing for future
pandemics.
For example, in Australia, the very low rates of death from
influenza and other respiratory diseases (fewer than ‘expected’ deaths) in 2020
may provide evidence of the effectiveness of the public health interventions
introduced to limit the spread of COVID-19 (for example, the restrictions on
public gatherings and movement including limiting numbers at venues, working
from home, and border closures), as the restriction periods correlate to lower
infection rates of other airborne viruses.
What data is
used to estimate excess deaths?
Australian
Bureau of Statistics (ABS) – Deaths
Within months of the first recorded cases of COVID-19 in
Australia, the ABS began reporting Provisional Mortality Statistics, to
provide more timely information on mortality patterns during the pandemic. This data, along with detailed data on
recent deaths and reliable population estimates by age, can offer insights into
what deaths might be expected under usual circumstances.
The official
mortality figures for 2022 will be released in the annual ABS Deaths and Causes of Death datasets (published later in 2023). Revised causes of death
data for 2021 was released in April 2023.
How are the
‘expected’ and the ‘unexpected’ or ‘excess’ deaths calculated?
There is no ’standard’ way of estimating the expected number
of deaths used to calculate excess deaths which is why there are various
estimates of excess deaths for a given country over a given period.
ABS
baseline estimates from historical averages
The ABS Provisional
Mortality Statistics for January to December 2022 reports a baseline
estimate of ‘expected deaths’ by taking the average (mean) number of weekly
deaths occurring in 2017–2019 and 2021. Data from 2020 is not included in this
baseline because the number of
deaths was significantly lower than expected, especially during winter.[2]
These baseline estimates can be used as a proxy for the
expected number of deaths, an indicator of higher or lower expected mortality. The ABS Provisional Mortality Statistics baseline for 2022 includes data recorded during the COVID-19 pandemic
(2021) and is not adjusted for population size and age structure.
The ABS explicitly states the Provisional
mortality publication estimates should not be used as official excess mortality
estimates. These figures are not adjusted for changes in age structure which
may overestimate excess deaths, as an older population can expect increasing
numbers of deaths relative to its population size.
In the article Measuring Australia's excess mortality during the
COVID-19 pandemic until the first quarter 2023 the ABS have modelled the number of expected deaths (in the absence of
the pandemic or an epidemic) based on a model developed for identifying excess
deaths from influenza (see Table 1). This model uses the average number of
deaths in the same weeks in 2013 to 2019 to create a baseline measure with
upper and lower bounds, but it smooths out the ‘outliers’ or high number of
deaths from the 2017 influenza epidemic to work out whether the variation is
falling outside the probable variation in deaths in any given week in the
absence of an epidemic. Estimates are age-adjusted to account for differences
in the age composition of the population.
Actuarial
estimates: Australian Actuaries Institute
Actuaries evaluate risks (including the risk of death) by applying
mathematical, statistical, economic, and financial analyses to business
problems in the insurance, superannuation, health financing, and other fields.
Actuaries from the (non-government) Australian Actuaries Institute have
formed a COVID-19
Mortality Working Group which produces an analysis of excess
mortality, using the ABS provisional mortality data.
The COVID-19
Mortality Working Group analysis
uses a 2015-19 expected deaths baseline and adjusts for population size and
ageing (unlike the ABS provisional deaths baseline).
This analysis gives a lower
estimate for 2022 than the ABS provisional estimates but a higher
estimate than the ABS modelled estimates (using different assumptions), as
shown in Table 1.
How many
excess deaths occurred in Australia in 2022?
Media and broader public discussion of ‘excess deaths’ followed
the ABS publication of provisional
mortality data for the six months to June 2022 which indicated there had
been 17% more deaths than in previous years (based on a four-year historical
average (2017-19 and 2021)).
The actuarial estimates
of excess mortality for the same six months estimated 13% more deaths than
expected (based on a 2015-19 average adjusted for population size and ageing) and
offered additional insights into how the pandemic was affecting mortality and which
people and institutions were most at risk. Table 1 shows the different
estimates for the first 6 months of 2022, and all of 2022.
Table 1. Estimates
of ‘excess’ mortality by time period and modelling assumptions
Sources: Australian Bureau of Statistics Provisional
Mortality Statistics (various releases) COVID-19 Mortality Working Group COVID
19 Blog
Australian Bureau of Statistics, Measuring
Australia's Excess Mortality During the COVID-19 Pandemic Until the First
Quarter 2023, Excess
mortality, Australia and by state, Jan 2013 – Mar 2023 (data download), (Canberra:
ABS, 2023)
The ABS article Measuring
Australia's excess mortality during the COVID-19 pandemic until the first
quarter 2023 (published in July 2023) offers an estimate of
excess deaths for all of 2022. Like the COVID-19 Mortality Working Group,
this ABS analysis uses baseline data prior to the COVID-19 pandemic but
incorporates different methodological assumptions. This analysis suggests
excess mortality in 2022 was just under 11% (10.9% as shown in Table 1).
Table 2 taken from the same ABS analysis shows
the effects of the pandemic have varied across Australian states and indicates
COVID-19 is still having an effect on mortality in the first quarter of 2023.
Table 2.
Excess mortality as a percentage above expected by jurisdiction, 2020-23
| |
2020 |
2021 |
2022 |
Jan -Mar 2023 |
| Australia |
-3.1 |
1.4 |
10.9 |
9.1 |
| New South Wales |
-4.1 |
0.1 |
10.7 |
8.6 |
| Victoria |
-0.9 |
3.4 |
13.2 |
12.0 |
| Queensland |
-4.3 |
0.8 |
10.1 |
7.8 |
| South Australia |
-3.2 |
0.5 |
9.2 |
8.9 |
| Western Australia |
-3.9 |
0.6 |
6.2 |
6.1 |
| Tasmania |
-3.6 |
5.8 |
13.6 |
17.3 |
| Northern Territory |
1.5 |
6.8 |
10.6 |
np |
| Australian Capital Territory |
-4.3 |
-2.8 |
12.1 |
8.9 |
Source: Australian Bureau of Statistics, Measuring
Australia's Excess Mortality During the COVID-19 Pandemic Until the First
Quarter 2023, (Canberra: ABS, 2023)
Notes: Data is provisional and subject to change. Years are
based on a sum of ISO weeks derived from the weekly modelling. There are 53
weeks in 2020. There are 52 weeks in 2021 and 2022. Excess mortality has been
estimated for the first 12 weeks of 2023, np = not published. Deaths in 2023
are deaths that occurred by 26 March and were registered and received by the
ABS by 31 May 2023.
What were
the main causes of the excess deaths in Australia in 2022?
The Provisional Mortality Statistics reports on selected
causes of death by underlying cause for doctor-certified deaths. The underlying
cause of death is ‘the disease
or injury that initiated the train of morbid events leading directly to death’,
with other causes recorded on the death certificate seen as contributing to the
death. Table 3 shows provisional 2022 data for common causes of doctor
certified deaths, including COVID-19, and the baseline averages for the same
diseases. The difference between the two is indicative of a changing pattern of
mortality and not an estimate of excess deaths.
Table 3. Doctor
certified deaths, selected causes of death, January to December 2022
| |
2022 |
2022: Baseline average |
Difference between certified deaths and
baseline estimate |
| Cancer |
50,314 |
47,614 |
2,700 |
| Dementia |
16,909 |
14,680 |
2,229 |
| Respiratory
diseases |
14,377 |
14,146 |
231 |
| Chronic lower
respiratory diseases |
8,013 |
7,719 |
294 |
| Influenza and
pneumonia |
2,614 |
3,024 |
-410 |
| Ischaemic heart
disease |
14,930 |
14,545 |
385 |
| COVID-19 |
9,732 |
n.a. |
.. |
| Cerebrovascular
diseases |
9,296 |
9,515 |
-219 |
| Diabetes |
5,598 |
4,698 |
900 |
Source: Australian
Bureau of Statistics, Provisional Mortality Statistics,
January to December, 2022, (Canberra:
ABS, 2023) with additional work by the Parliamentary Library.
Notes: Only doctor-certified deaths are included. Data is by date of death
(occurrence). The baseline includes deaths from 2017-19 and 2021, averaged to
remove year on year fluctuations in death numbers. COVID-19 deaths are not
included in the baseline as only one year of data is available. As the baseline includes 2021 data it is not measuring
excess mortality in the absence of the COVID-19 pandemic. Other estimates of
excess mortality should be used for this purpose.
In a 2023 online article, Confirmation
of 20,000 excess deaths for 2022 in Australia, the COVID-19 Mortality Working
Group estimate COVID-19 infection was the most
common cause of excess deaths in Australia in 2022. The analysis estimates
deaths from COVID-19 (10,300 deaths) represent just over half of all excess
deaths and there were another 2,900 excess deaths where COVID-19 was a
contributing factor.
For the excess deaths in 2022 where COVID-19 was not the
underlying or a contributing cause, the working group considered the mostly
likely reasons to be:
-
The impact of [having had] COVID-19
on subsequent mortality risk, particularly heart disease, stroke, diabetes and
dementia, which have all been identified in studies
-
Delays in emergency care,
particularly at times of high prevalence of COVID-19 and/or influenza, and
-
Delays in routine care, which
refers to missed opportunities to diagnose or treat non-COVID-19 diseases and
the likelihood of consequent higher mortality from those conditions in future.
The analysis also reports correlations that may help to
identify the drivers of mortality changes, noting:
-
deaths with COVID-19 have followed
the same pattern as deaths from COVID-19 in 2022
-
non-COVID-19 excess deaths have
been highest when there have been peaks in COVID-19 deaths and peaks in
influenza deaths
-
deaths due to some causes
(dementia in particular) are closely correlated to the level of respiratory
disease (including COVID-19) circulating
-
non-COVID-19 excess deaths are
less apparent when there is no or little COVID-19 circulating, as illustrated
by the difference between Western Australia and the other states in early 2022.
What effects
will the pandemic have on mortality in the future?
On 5 May 2023 the
WHO determined ‘that COVID-19 is now an established and ongoing health
issue which no longer constitutes a public health emergency of international
concern’. However, it also noted ‘SARS-CoV-2 is expected to continue
circulating for the foreseeable future’ and urged governments to maintain
and strengthen systems for surveillance.
Recent Australian case numbers and deaths suggest
the effects of COVID-19 will continue into 2024. The ABS
have reported that from March 2020 to June
2023:
-
18,922 deaths[3] where
people died with or from COVID-19
-
The underlying cause of death for
14,941 (79.0%) of these people was COVID-19
-
There were a further 3,981 people
who died of other causes (e.g., cancer) but COVID-19 contributed to their death
-
Chronic cardiac conditions were
the most common pre-existing chronic condition for those who had COVID-19
certified as the underlying cause of death.
Using updated data and modelling for 2023,
the COVID-19
Mortality Working Group report that excess
mortality in the first 6 months of 2023 was mainly due to COVID-19. There
were 5,500 more deaths than would have been expected without the pandemic, and
more than half of these were deaths from COVID-19.
The actuarial analysis reported in the article Counting the toll
of COVID notes the prevalence and severity of future COVID-19 strains
will affect the number of COVID-19 deaths. However, it is not clear what the
other longer-term effects of the pandemic on mortality will be. It notes future
mortality rates may also change due to the longer-term effects on people’s
health of having delayed medical care in 2021 and 2022, as well as the effects
of having been ill with COVID-19.
Further
information
Australian data
and resources on COVID-19 and excess deaths
Actuarial analysis
-
COVID-19
Mortality Working Group, COVID-19
Blog, Actuaries Digital
-
Jennifer Lang, Karen Cutter and Richard Lyon, Excess
Mortality in Australia, COVID-19 Actuaries
Response Group, 18 October 2022
-
Karen Cutter, Richard Lyon and Jennifer Lang, Counting the toll of
COVID, Croakey Health Media, 22
March 2023
Statistics
Australian Bureau of Statistics (ABS)
Australian Institute of Health and Welfare,
Australia’s
health 2022 data insights, 7 July 2022
International
data and resources on COVID-19 and excess deaths
World Health Organization
Our World in Data
National Center for Health Statistics (USA)
(updated monthly) Excess
Deaths Associated with COVID-19 - Provisional Death Counts for Coronavirus
Disease (COVID-19)
Office of
National Statistics (United Kingdom)
The Economist, Tracking
COVID-19 excess deaths across countries, 20
October 2021