The Changing Nature of Life Expectancy and Causes of Death in Ireland 1922-2023

Sources and methodology

Death data

The Changing Nature of Causes of Death and Longevity in Ireland, 1922-2023 is based on tables in the 1922-2023 series of deaths in Ireland. These originated in a registered death tables published in the 'Annual Report of the Registrar-General of Marriages, Births and Deaths in Ireland' which were compiled and  published by the Registrar General for reference years from 1922 to 1952, and the 'Annual Report on Vital Statistics' published by the Central Statistics Office from reference year 1953 onwards. The series from 1953 onwards was prepared by the Central Statistics Office for the Minister for Social Protection in accordance with the provisions of Section 2 of the Vital Statistics and Births, Deaths and Marriages Registration Act, 1952 and Government Order SI 831 of 2007. The figures refer to deaths by date registered. These may differ from deaths by date occurred.

Figures for the number of deaths from 1922 to 1979 have been transcribed from the various Annual Report publications over the period. Figures for 1980 to 2006 come from the PxStat table VSD55, figures for 2007 to 2022 come from VSA35, while figures for 2023 come from VSA29.

All death rates per 100,000 of population have been calculated by utilising the estimated population time series in the 1950 Annual Report for the period 1922 to 1950 and PxStat table PEA11 from the period 1951 to 2023.

Classification of Cause of Death Data

From 1922, different versions of the International Classification of Diseases Classification System were used in the Irish Free State, then the Republic of Ireland. Deaths would be classified using these different versions. The major changes in ICD versions (seven different versions appear over the time period) mean that great care must be taken in comparing cause of death classifications over time. The history of ICD versions used in this release, and the impacts of these versions on Cause of Death classification, is discussed in the section below 'Changes in Cause of Death Classification Methods over time'.

Three different causes of death are examined in this publication. These are, cancer, heart disease and tuberculosis. The following ICD-9 codes were taken from the period 1980 to 2006 VSD55 for cancer (140-208), heart disease (393-398,410-429) and tuberculosis (010-018,137). For 2007 to 2023 the following ICD-10 codes were taken from VSA35 and VSA29 for cancer (C00-C97), heart disease (I05-I09,I20-I28,I30-I33,I39-I52) and tuberculosis (A15-A19,B90). 

Life Table Data

The longevity data was obtained from the published Irish Life Tables 1 through 17. A ‘Life Table’ refers to a table of statistics related to life expectancies for different categories of people.  Period life expectancy is the average number of years a person would live if they experienced age-specific mortality rates for that time period throughout their life.  Therefore, it is not the number of years someone of that age could expect to live, given that deaths rates are likely to change in the future, for example, due to advancements in the field of medicine. In other words, Irish Life Table 1 shows the life expectancy based on the death rates encountered in the 1925-1927 period whereas Irish Life Tables 17 were constructed for males and females which are representative of the mortality experience in Ireland in 2016 by using the 2015, 2016 and 2017 estimates and census of population (usually resident) and deaths registered in the three years.  The life table should reflect the normal mortality conditions at about the time of the Census.

The basic assumption in a Life Table is as follows. Firstly, a given cohort of births, (100,000), start in a specific year.  The mortality rates for each age for the relevant three year period (say 2015-2017) are used to calculate how many of the cohort will reach each year of age until eventually all members of the cohort have died.  This enables the total number of years lived by the cohort to be calculated. When this total is divided by the number of persons in the cohort, (100,000), the result is the average number of years lived in the cohort, or the mean expectation of life at birth.  The total number of years lived by the cohort from any given age can also be calculated and, when divided by the number of survivors in the cohort entering upon that year of age, the figure obtained is the expectation of life in years for those persons.

Changes in Cause of Death Classification Methods over time

Systematic Cause of Death classification efforts began in earnest in the 18^th Century with the work of François Bossier de Sauvages de Lacroix, a French botanist and professor of pathology who developed the first scientific nosology – or system of classifying diseases. This was followed by later work by William Cullen which in turn led to the subsequent work of the General Register Office of England in Wales in the 19^th Century – where the medical statistician William Farr progressed the classification of death greatly.

However, the main driver in modern cause of death classification has been the International List of Causes of Death – which was pioneered by the International Statistical Institute. The French Statistician Bertillion began in 1891 the work of formulating a formal International List of Causes of Death. This was accepted by the American Public Health Association in 1898. A general approach featuring decennial revisions was accepted. This was the first ICD and led to revisions in 1900 (ICD-1), 1910 (ICD-2) and 1920 (ICD-3). Irish death statistics have used various versions of the ICD. The full timeline is as follows:

Since each classification has significant variation in structure, this has major implications for comparability over time.

How does ICD-10 operate

The Underlying Cause of Death (UCOD) has been defined by the World Health Organisation (WHO) as

(a) the disease or injury which initiated the train of morbid events leading directly to death,

or

(b) the circumstances of the accident or violence which produced the fatal injury.

The UCOD is selected for routine single-cause tabulation of mortality statistics.

All deaths registered in the quarter have been included in the statistics and some cases have been assigned a provisional cause of death pending the outcome of further enquiries.

Inquest deaths are coded manually due to the nature of the reporting of these cases. The difficulty lies in automatically assigning a verdict from a broad range of verdicts open to a Coroner or jury which include accidental death, misadventure, suicide, open verdict, natural causes (if so found at inquest) and in certain circumstances, unlawful killing. A provisional cause of death may be assigned to a number of inquest cases pending the outcome of further enquiries.

Deaths assigned an Underlying Cause of Death of External causes of injury and poisoning (including deaths from road traffic accidents and deaths from intentional self-harm), are likely to be underrepresented as such deaths are reported to the Coroner’s Office for further investigation. This can then result in such deaths being registered late (more than three months after the date of occurrence) and therefore have not yet been reported to the CSO.

From 01 January 2018 the CSO is using IRIS software to assign the UCOD. IRIS is a European-developed automated coding software, endorsed by Eurostat and is maintained by the IRIS Institute and all WHO updates to the ICD-10 classification are accounted for in IRIS according to the WHO timelines

Cause of Death Determination Process

From the 01 January 2018 the CSO is using new automated software called IRIS for selecting the underlying cause of death code (UCOD). The IRIS Coding System has been developed by the IRIS core group to code mortality data and is the preferred coding tool for European countries.

The mortality coder when coding inquest cases in the CSO examines both the Coroner's Certificate and Form 104, where applicable, and assign ICD-10 classification codes to all other reported conditions and select the UCOD, defined as:

(a) the disease or injury which initiated the train of morbid events leading directly to death, or (b) the circumstances of the accident or violence which produced the fatal injury.

The mortality coders apply the W.H.O international mortality coding instructions pre-supposing that data has been collected with a death certificate conforming to the International Form of Medical Certificate of Cause of Death as recommended by the WHO. It is the responsibility of the medical practitioner or other qualified certifier signing the death certificate to indicate which morbid conditions led directly to death and to state any pre-existing conditions giving rise to this cause, see: ICD 11 Mortality and Morbidity Reference Guide

These are key to the correct assignment of the underlying cause of death and the hierarchy in which the causes are written on the death certificate impacts on the assignment of the UCOD.

If the Coroner's Certificate provides enough information to assign a statistical cause of death code, it is not necessary for the CSO to issue a Form 104 to the Gardai. If there is not enough information provided by the Coroner's Certificate, then it is necessary for the CSO to issue a Form 104. When assigning a cause of death code, if the Coroner's Certificate does not mention suicide but the Garda states on Form 104 that the death was as a result of intentional self-harm, the statistical cause of death is coded as suicide. 

The classification system used for cause of death is 10^th revision of the International statistical classification of diseases and related health problems, see: ICD 10 Classification Coding Dictionary.