Cape Town | Excess mortality is a term used in epidemiology and public health that refers to the number of deaths that are occurring beyond what we would have normally expected. It is used to measure the mortality impact of a crisis when not all causes of death are known. In 2020, excess mortality is considered in the context of the current COVID-19 pandemic.
The World Health Organization defines ‘excess mortality as: “Mortality above what would be expected based on the non-crisis mortality rate in the population of interest. Excess mortality is thus mortality that is attributable to the crisis conditions. It can be expressed as a rate (the difference between observed and non-crisis mortality rates), or as a total number of excess deaths.”
The South African Medical Research Council’s (SAMRC) Burden of Disease Research Unit, which provides information on the trends in the country’s health status, conducted a study on Excess Deaths for South Africa and published our findings in a press release titled: Weekly Deaths suggests higher numbers of COVID-19 deaths. The SAMRC, is an entity that reports to the National Department of Health and has provided this service to the country for many decades.
“The SAMRC like other state agencies globally, tracks the count of deaths. This analysis has generally demonstrated that during the pandemic, countries experience excess numbers of deaths over and above confirmed COVID-19 deaths,” says Prof Debbie Bradshaw, Chief Specialist Scientist and Epidemiologist at the SAMRC.
According to a publication in ourworldindata.org: “excess mortality can only be calculated on the basis of accurate, high frequency data on mortality from previous years” and that “few countries have statistical agencies that have the capacity to report the number of people who have died in a given month, week or even day to day. For most low- and middle-income countries such data is not available for the last years.”
“It is therefore one of government’s key successful outcomes that we have built the necessary capacity and infrastructure, as a middle income country, to afford ourselves the opportunity to augment our epidemiological surveillance, says Minister of Health Dr. Zweli Mkhize. “We are privileged to have robust academic agency that allows us to comprehensively study the impact of COVID-19 in South Africa. Being able to track excess deaths is part and parcel of our armament- the excess deaths gives us a perspective on the true impact of the virus on our health care system and society, while the recorded deaths gives us details of the pathology itself and allows us to understand the natural history of the disease, associated co-morbidities and the efficacy of treatment regimens,” he adds.
South Africa has a well-established civil registration and vital statistics system. All deaths must be registered with the Department of Home Affairs: a death notification form including information about the medical cause of death must be completed by the certifying doctor submitted by a next of kin or their undertaker to the Department. The forms are subsequently provided to Statistics South Africa for capturing, processing, assessment, analysis and dissemination of statistical reports and datasets on mortality and causes of death.
The Burden of Disease Research Unit works closely with UCT’s Centre for Actuarial Research to provide a weekly report of the number of deaths in South Africa. These are based on the numbers of deaths registered by the Department of Home Affairs on the National Population Register. Deaths are classified and analysed by date of occurrence and not the date of registration. The numbers have been adjusted for deaths that are not registered as well as the people who do not have a South African ID number, based on consolidated demographic assessment of the data over the past 10 years.
Although this data does not have information about the medical cause of death (apart from whether the cause was natural or unnatural), the data is invaluable as it provides a near real-time count of the total numbers of deaths from natural and unnatural causes.
This same surveillance also demonstrated the rapid decrease in unnatural deaths with the implementation of a hard lockdown, and the return to usual numbers following the lifting of a hard lockdown and the restrictions on alcohol, with a sudden increase in the first week of June. It was this evidence that supported the re-institution of suspension of alcohol sales, for example.
Excess deaths can be calculated in different ways. Some analysts take the excess above the expected number based on historical data while others argue that the number should be those above a threshold such as the upper prediction bound i.e. significantly higher than expected. And, in general, these excess deaths are calculated using all-cause mortality. Thus it is considered that excess deaths would comprise COVID-19 deaths that are confirmed, COVID-19 deaths that have not been confirmed as well as other deaths that may arise from conditions that might normally have been diagnosed and treated had the public been willing and able to access health care.
In the UK, for example, it was realised that the confirmed COVID-19 deaths reflected only the COVID-19 deaths that occurred in the health services and that deaths that occurred in long-term care institutions and at home were not included in their COVID-19 statistics. However, given the availability of near-real time cause of death data from the death registration process in the UK, they were able to add such deaths to their confirmed COVID-19 statistics. Even after this they found that there were still excess deaths over and above these COVID-19 deaths, which are assumed to be deaths from conditions that might normally have been diagnosed and treated had their hospitals not been overwhelmed.
Faced with the challenge that South Africa had a stringent lockdown in the very early stage of the epidemic and that unnatural deaths are a higher proportion of the all-cause mortality than in developed countries (and were impacted very significantly by the stringent lockdown), the SAMRC-UCT team thought it was necessary to use a different approach. To quantify the impact of the COVID-19 epidemic on South African deaths, it was decided to focus on deaths from natural causes and remove the impact of changes in the unnatural deaths.
In addition, it was necessary to consider that the lockdown had reduced the number of natural deaths. In the early stage, this was well below the predicted numbers of deaths. Thus, a baseline was chosen that was consistent with the level that the number of natural deaths was tracking prior to the uptick in the trend.
“It is not unexpected that the excess natural deaths reported are higher than the official COVID-19 deaths report,” says Prof Glenda Gray, SAMRC President and CEO. “All countries are grappling with how to report excess mortality. Definitions and calculations should be consistent globally and locally. Our excess deaths will be different, given the demographics of our country, and compared to countries like the United Kingdom, appear at this stage of the pandemic to be less,” explains Gray.
It is important to note that the excess cumulative numbers of natural deaths include more than direct and indirect COVID-19 deaths. In particular, they include deaths arising from constraints on health resources. It is also important to point out that the excess deaths are classified by date of occurrence of the death while the confirmed COVID-19 deaths are classified by date of reporting by the Ministry of Health.
Factors that may contribute to observed excess deaths include:
- People dying from COVID-19 before they get to the health care facility. This may be due to lack of transport, delays in transport and/or hospitals being unable to receive them.
- People dying from COVID-19 but the death not being reported as such. This may be due to test results not being available at the time of death and/or challenges in the provincial COVID-19 reporting systems.
- People dying from non COVID-19 conditions because the health services have been re-orientated to COVID-19. Examples include people who have not been diagnosed with TB and others with current TB who have defaulted on treatment for fear of attending the health services.
These phenomena are not unique to South Africa and have been observed or postulated globally by countries that are able to track their excess mortality. By making these observations, governments are able to hone in on their unique issues contributing to excess deaths and therefore strengthen their health systems and monitoring and surveillance capacity.
“We need to work with Home Affairs and Stats SA to find a way to get quick access to the medical information that doctors provide on death certificates so that we can understand exactly what are the causes of death of adults and especially older adults. We urge our doctors to ensure accurate completion of deaths certificates especially if it is COVID-19 related,” said Gray.
Estimating COVID and collateral deaths in South Africa (Presentation) - Rob Dorrington
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