Written answers

Wednesday, 22 January 2025

Photo of Peadar TóibínPeadar Tóibín (Meath West, Aontú)
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1481. To ask the Minister for Health the level of excess deaths that occurred in Ireland in each of the past ten years; and the details of the cases of the excess deaths for each year. [1059/25]

Photo of Stephen DonnellyStephen Donnelly (Wicklow, Fianna Fail)
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The Department of Health does not produce estimates of excess mortality. However, the Department works closely with the HSE-Health Protection Surveillance Centre (HPSC) and other stakeholders to monitor estimates of excess mortality.

Excess mortality is a term used in epidemiology and public health that refers to the number of deaths from all causes during a period of time above and beyond what we would have normally expected to see. Excess deaths are typically defined as the difference between the observed number of deaths in a specific time period and the expected number of deaths in the same time period.

A number of different methodologies have been developed internationally to try to estimate levels of excess mortality. All of these methodologies are statistical techniques to estimate excess mortality based on all-cause mortality data, they do not identify individual deaths as ‘excess deaths’ it is therefore not possible to provide ‘details of the cases of the excess deaths’.

It is also important to note that the different estimation methods vary, for example in the years which are used to estimate a baseline, in how they estimate what is the level of ‘expected’ deaths, if they apply a statistical significance test and if they take account of demographic change. There is therefore no single source of data on estimated excess mortality and different estimates exist.

The HSE-Health Protection Surveillance Centre (HPSC) receives daily registered deaths data from the General Register Office (GRO) on all deaths from all causes registered in Ireland. These data have been used since 2009 to monitor excess all-cause deaths in Ireland as part of a wider European Mortality Monitoring Project known as EuroMOMO (www.euromomo.eu/). EuroMOMO is a European mortality monitoring activity, aiming to detect and measure excess deaths related to seasonal influenza, pandemics and other public health threats. EuroMOMO publishes a weekly update of estimates of excess mortality, by age group, for all participating European countries www.euromomo.eu/graphs-and-maps. This is the main indicator of excess mortality used in Ireland.

EuroMOMO publish estimates in the form of z-scores. A z-score is a statistical measure that describes how far away from the mean a given data point is. In this context, if the observed number of deaths is the same as the expected number of deaths, the z-score is 0. The greater distance the observed number of deaths is from the expected number (either above or below), the higher the z-score will be (with either positive or negative sign respectively).

Data on the weekly EuroMOMO z-score for Ireland for the 10 years 2015-2024 is attached, as well as chart (Chart 1). This analysis was conducted on 16th January 2025 by the HSE-HPSC excess mortality team and includes data on all registered deaths up to the 12th January 2025. It was not technically possible to run the model for all deaths between 2015-2024 so two separate models were run. Z-scores from 2015-2016 were extracted from a model run on 03/07/2024 and z-scores from 2017-2024 were extracted from a model run on 13/01/2025.

A z-score of > 2 indicates excess mortality. Weeks where the z-score is less than or equal to 2 are considered to not have any excess mortality. Where the z-score is greater than 2 but less than or equal to 4 is considered to be low excess; greater than 4 but less than or equal to 7 is considered to be moderate excess; and a z-score of 7 or higher is considered high excess. During the 10 years 2015-2024: High estimated excess mortality (above the red line in Chart 1) was recorded in Ireland during Weeks 14-16 2020, Weeks 02-04 2021 and Weeks 51-52 2022. Moderate estimated excess mortality (between the green and red lines in Chart 1) was recorded during Weeks 01-03 2017, Weeks 52 2017 – Week 05 2018, Week 17 2020, Weeks 05-06 2021, Week 15 2022 and Weeks 01-02 2023. Low estimated excess mortality (between the blue and green lines in Chart 1) was recorded during an additional 39 weeks over the 10-year period. Mortality has either been within or below the ‘normal range’ for all other weeks (below the blue line in Chart 1). Excess mortality has been observed during periods when influenza viruses circulated at high levels in Ireland, and during certain periods of the COVID-19 pandemic.

It should be noted that for more recent periods, these data are provisional due to the time lag with death registration in Ireland. A country-specific adjustment function was applied to correct for the typical lag in registrations of deaths in Ireland (the legal period for death registration in Ireland is currently three months). Nonetheless, estimates of excess mortality for the most recent weeks are reported with some uncertainty and should be interpreted with caution.

Other estimates of excess mortality in Ireland have also been published by the OECD, WHO, Eurostat, CSO, The Lancet and other researchers. The Department of Health is actively monitoring and reviewing all available data on mortality as it becomes available to gain a better insight on the underlying mortality trends and factors influencing these.

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