Objective: To compare and contrast the Classification of Causes of Historical Mortality (CCHM) with the International Classification of Diseases 4th Revision (ICD-4) as methodological elements that can be implemented in historical mortality studies.
Materials and methods: We conducted a longitudinal descriptive study of the causes of death in two different localities in Spain, namely, Cadiz and Vejer de la Frontera (1900-1950), to compare the International Classification of Diseases 4th Revision (ICD-4) and the Classification of Causes of Historical Mortality (CCHM). This study proposes the CCHM and its use in statistical analyses of mortality, especially from the mid-19th century to the second half of 20th century. It is a methodological instrument based on the theoretical precepts of Thomas McKeown, expanded through knowledge gained in studies of historical mortality and contrasted with editions of the ICD.
Results: The results showed several differences between the ICD-4 and the CCHM. The ten main causes of death (CoDs) in the CCHM account for 74.3% in Cadiz, compared to 56.6% accounted for by the ICD-4. According to the ICD-4, the number of infectious CoDs exceed the number of noninfectious ones in Cadiz every year. On the other hand, based on the CCHM, we observed that while infectious CoD causes of death predominated over noninfectious ones, there was a change in trend, with noninfectious CoDs predominating the following year. During the interval from 1915 to 1937 in Vejer de la Frontera, there were 12 deaths due to ill-specified causes (ICD-4: 18.200) and 0 due to ill-defined causes (CCHM: 3.0.0.0).
Conclusions: The CCHM accurately determines the differences between infectious and noninfectious causes of death and explains sociodemographic and health-related aspects in the population and its use in employment, illegitimacy or place-of-death studies. Moreover, it has more advantages, such as the incorporation of new diagnostic expressions, and it can be constantly updated, thus facilitating its use over long periods of time.