Cause of death

For national mortality statistics, every death is attributed to one underlying condition, based on information reported on the death certificate and using international rules for selecting the underlying cause of death from the conditions stated on the certificate. The underlying cause is defined by the World Health Organization as “the disease or injury that initiated the train of morbid events leading directly to death, or the circumstances of the accident or violence which produced the fatal injury.” Generally, more medical information is reported on death certificates than is directly reflected in the underlying cause of death. Conditions that are not selected as the underlying cause of death constitute the nonunderlying causes of death, also known as multiple cause of death.

Cause of death is coded according to the appropriate revision of the International Classification of Diseases (ICD) (see Sources and Definitions, International Classification of Diseases [ICD]). Effective with deaths occurring in 1999, the United States began using the 10th revision of ICD (ICD–10); during 1979–1998, causes of death were coded and classified according to the 9th revision (ICD–9). COD-Table lists ICD codes for the 6th through 10th revisions for causes of death shown in Health, United States. In Health, United States, common terms are sometimes used in the text in place of medical terminology. Examples include cancer for “malignant neoplasm” and kidney disease for “nephritis, nephrotic syndrome and nephrosis.”

Each ICD revision has produced discontinuities in cause-of-death trends. These discontinuities are measured by using comparability ratios that are essential to the interpretation of mortality trends. (Also see Sources and Definitions, Comparability ratio.) For further discussion, see: Comparability of Cause-of-death Between ICD Revisions. (Also see Sources and Definitions, Comparability ratio; International Classification of Diseases [ICD]; and National Vital Statistics System [NVSS]: Multiple Cause-of-Death File.)

… Category not applicable; cause-of-death codes are not provided for causes not shown in Health, United States.
* Categories for coding human immunodeficiency virus (HIV) infection were introduced in 1987. The asterisk (*) indicates codes that were not part of ICD–9 (International Classification of Diseases, Ninth Revision).
† In ICD–9, a definitive diagnosis was required for classification as Alzheimer disease. Terms such as ‘‘Alzheimer-type dementia’’ or ‘‘Alzheimer dementia’’ were classified as Presenile dementia rather than Alzheimer disease. In addition, in ICD–9, if an unspecified chronic organic psychotic condition (294.9) is mentioned with Alzheimer disease, the two conditions form a linkage and are coded to 290.1 (Presenile dementia). Under ICD–10, this linkage does not exist and restrictions regarding definitive diagnosis are relaxed, so any mention of Alzheimer is classified as Alzheimer disease (G30). This involves the reclassification of nearly all cases of Presenile dementia to Alzheimer disease.
§ Starting with 2007 data, the National Center for Health Statistics introduced the category J09 for coding avian influenza virus. In 2009, the title for ICD–10 code J09 was changed from “Influenza due to identified avian influenza virus” to “Influenza due to certain identified influenza virus” to accommodate deaths from influenza A (H1N1) virus for data years 2009 and beyond.
¶ On March 11, 2020, COVID-19 was declared a pandemic by the World Health Organization. Starting with 2020 data, the National Center for Health Statistics introduced the code U07.1 for COVID-19.
** Under ICD–9, this category is called Fetal and neonatal hemorrhage.
†† Starting with 2001 data, the National Center for Health Statistics introduced categories *U01–*U03 for classifying and coding deaths due to acts of terrorism. The asterisk (*) indicates codes that are not part of ICD–10.
§§ The public health community prefers “unintentional injuries” to “accidents” and “motor vehicle-related injuries” to “motor vehicle accidents.”

SOURCES: National Center for Health Statistics. Advance Report: Final Mortality Statistics, 1974; Deaths: Final Data for 1997; Comparability of Cause of Death Between ICD–9 and ICD–10: Preliminary Estimates; Deaths: Final Data for 2003; Deaths: Final Data for 2010; Deaths: Final Data for 2019; Mortality in the United States, 2022.