Excess deaths from all causes, involving and with dementia as the underlying cause: Scotland 2020-2022

Limitations

Data relating to dementia

Not every individual with dementia has a medical diagnosis. Depending on the method used to estimate prevalence, it is estimated that between 60% (EuroCoDe) and 85% (PACSIm) of people aged 65+ with dementia in Scotland receive a medical diagnosis. PACSIm is the benchmark used by NHS England, while Alzheimer Scotland prefers EuroCoDe.

Further, even if a person has received a medical diagnosis of dementia, this does not mean it will be recorded on the death certificate unless determined as a contributing cause of death. NRS provide information about the recording of diseases and conditions on death certificates.

This means that some people who die with dementia as a pre-existing medical condition will not be included in official statistics that record deaths related to dementia because: either i) dementia was not considered as a contributory factor associated with the person's death, or ii) the person did not receive a formal diagnosis. While the underreporting of dementia will understate the true rate of deaths involving dementia in mortality data, this limitation should not impact on the conclusions made when comparing average deaths over recent years, since estimated diagnosis rates remain broadly the same over that time.

Excess deaths as a measure of the impact of the pandemic

The measurement of excess deaths is increasingly used to assess the impact of the pandemic. Large international studies have now been published, including analysis of global excess deaths by the World Health Organisation^[3], and it is a continuously evolving picture of methodology development to understand the effects of COVID-19 on mortality within and across nations.

On methodological issues, usually the previous five years are used to compare against the most recent year to calculate excess deaths. In 2020, excess deaths were measured by comparing the 2020 figure against the average for 2015-2019.

However, as excess deaths are a key measure of the effect of the pandemic, it is not appropriate to compare the 2021 figure against the 2016-2020 average as that average will be affected by the pandemic with higher deaths in Spring 2020. NRS (as well as the Office for National Statistics (ONS) and Northern Ireland Statistics and Research Agency (NISRA)) therefore decided to continue to use the 2015-2019 average to measure excess deaths in 2021.

For 2022, the excess deaths calculation would usually incorporate the mortality data for the most recent 5 year period (2017-2021). However, given the unusual nature of the 2020 data and the decision previously taken for 2021, NRS (as well as ONS and NISRA) decided to use the average of 2016, 2017, 2018, 2019 and 2021, and therefore continue to exclude 2020 from the five-year average.

The effect of an ageing population means that the five year average number of deaths used for calculating excess deaths in 2015, 2016, 2017, 2018 and 2019 (2010-2014, 2011-2015, 2012-2016, 2013-2017; 2014-2018) increased by slightly over 1% each year. Therefore, by using the 2015-2019 average in 2021, there is a risk that we have overestimated excess deaths, by not fully accounting for the ageing population.

Relevant mortality statistics have limitations, specifically when it comes to assessing disease progression and lived experiences of people with dementia and adult care home residents who are often living with dementia. While these wider issues are critical, they are out of scope for this report. The parameters and remit of the report do not extend to the identification and analysis of wider harms that may have been caused by restrictions or disruption to essential health services and care as they relate to wider health outcomes and experiences.

The analysis enables us to consider the potential reasons for the trends observed from what we know was happening across the time periods covered in this analysis. This includes the wider context of vaccination programmes, increased testing and improved understanding of COVID-19 symptoms. However, we are unable to say definitively how the wider context influenced trends in excess deaths since this analysis is statistical and necessarily retrospective. For instance, as discussed in the published analysis of 'Excess deaths from all causes, involving and with dementia as the underlying cause: Scotland 2020/2021', a reduction in weekly average deaths involving dementia over the course of the pandemic may relate to the peak in excess deaths caused by dementia near the beginning of the pandemic. Some of these deaths may have been caused by COVID-19 with dementia as a contributory factor; however, the involvement of COVID-19 may not have been registered on the death certificate, with dementia assumed to be the underlying cause, since testing was less widespread outside hospital settings and there was less awareness of all COVID-19 symptoms. However, the level of COVID-19 involvement in these deaths registered with dementia as the underlying cause cannot be established categorically.

In addition, we are unable to determine the potential reasons for ongoing increased levels of excess deaths at home, both involving dementia and from all causes.

Issues relating to excess deaths in care homes

Measuring longer-term trends in mortality is appropriate to reduce the impact of random variation and recording issues that may occur in the reporting of weekly figures. In this context, it is relevant to highlight the potential impact of a fluctuating care home population, with a reduction in occupancy over time potentially influencing a reduction in excess deaths after the first wave of the pandemic.

As cited above, the estimated number of residents in care homes for older people decreased by 6%, from 32,445 to 30,502, between 2019 and 2021 (see the Public Health Scotland Care Home Census 2021). This population remained relatively stable between 2021 and 2022, with 30,552 residents in care homes for older people reported in the Public Health Scotland Care Home Census 2022, although the older adult care home population has decreased by 9% since 2012 despite an ageing population in Scotland. This reduction in occupancy may have impacted the statistics for when we have compared excess deaths between 2020 and 2021, as we would expect a lower number of deaths with reduced occupancy. Additionally, it is likely that the most vulnerable residents died earlier in the pandemic, which may have influenced the profile of residents at later stages of the pandemic i.e. to be younger and less clinically vulnerable.

Further, excess deaths is a broad measure of mortality that does not account for differences in the age of populations in different settings. For example, care homes have a population consisting of older and more clinically vulnerable individuals, and as such this population is likely to be disproportionally impacted by a virus such as COVID-19. There are also further issues related to difficulties of infection prevention in care homes, where close contact care is required, with the risk of an outbreak of COVID-19 infection increasing progressively as the size of the care home increases (see the Public Health Scotland report on discharges from NHSScotland hospitals to care homes between 1 March and 31 May 2020).

Notes on annual dementia death statistics published by NRS

The NRS report Alzheimer's disease and other dementias, published on 26 July 2022, shows that deaths registered with dementia as the underlying cause were 2% below^[4] the 2015-2019 average in 2021 and 3% above⁵ the 2015-2019 average in 2020. Deaths registered with dementia as the underlying cause were 10% higher in 2019 compared to the 2014-2018 average (see NRS table). This shows that excess deaths from dementia including Alzheimer's disease were lower in 2020 than in 2019 and sit within what might be expected as normal year-on-year variation. However, NRS note that these statistics are affected by a change in cause of death coding software at the beginning of 2017. For further comparison, annual excess deaths from all causes between 2001 and 2019 ranged from -4% to +6% (see supplementary table 5).