Leading Cause of Death in Ireland 1985-2005

Data Sources

The information contained within this publication and subsquent PxStat table comes from historical Vital Statistics Annual Reports. 

Cause of Death

All statistics relating to the underlying cause of death is coded under the International Classification of Diseases, Ninth Revision (ICD-9).

The main changes to the classification of diseases between ICD-9 and ICD-10 are as follows:

- ICD-10 has over 3,000 more codes than ICD-9
- Inclusion of additional underlying causes (e.g. AIDS/HIV, chromosomal abnormalities)
- Expansion of certain underlying causes existent in ICD-9, for certain diseases, providing for the recording of greater levels of detail (e.g. acute myocardial infarction, perinatal conditions, viral hepatitis)
- Movement of underlying causes of death between ICD chapters (e.g. haemorrhage moved from the circulatory chapter to the symptoms and signs chapter in ICD-10, certain disorders of the immune mechanism moved from the endocrine chapter to the blood chapter in ICD-10 and certain disorders of blood moved from the blood chapter to the neoplasm chapter in ICD-10)
- Contraction of certain underlying causes of death (e.g. autoimmune disease and connective tissue disease are given the same code in ICD-10)
- Changes in the inclusion and exclusion guidelines for certain underlying causes of death
- Re-ordering of certain chapters and underlying causes
- Alphanumeric codes used instead of numeric codes

Additionally, there have been changes to the selection rules applied to determine the underlying cause of death. The most significant change relates to Rule 3 which allows a condition from Part I or Part II of the death certificate to be selected as the primary condition if it is an obvious direct consequence of another reported condition. There are a number of guidelines presented for this rule, most significantly the guideline in relation to pneumonia. The effect of this rule change reduces the number of deaths assigned to pneumonia and alternatively assigns the underlying cause of death to the chronic debilitating disease.

Certain official updates to ICD-10 are also incorporated in the coding of the cause of death. In particular, mental and behavioural disorders due to psychoactive substance use (F10-F19), with mention of intestinal infectious diseases (A00-A09), accidental, intentional self and undetermined intent poisoning by and exposure to noxious substances (X40-X49, X60-X69, Y10-Y19) or assault by chemical or noxious substance (X85-X90), are now coded to the latter.

These changes have the effect of data being coded to different underlying causes of death at the most detailed level of ICD-10 and at the higher chapter level of ICD-10. For this reason, data cannot be easily compared across ICD-9 and ICD-10.