Triangle Simplex Plot for Representing Multiple Cause of Death Dynamics

Abstract

Underlying causes of death offer only a partial insight into cause-specific mortality trends. A complementary approach, known as multiple cause of death analysis, which includes all conditions listed on the death certificate, can deepen understanding of cause of death dynamics in at least two ways – through the development of mortality rates from contributory causes and the analysis of changes in the roles that diseases play in the lethal process. The objective of this paper is to revisit cause of death analysis in Czechia, Denmark and the United States (USA) over the last two decades, focusing on the context of underlying cause of death (UCD) mortality trends. This includes trends in contributory causes and changes in the roles played by causes of death in the death process. We use a visualisation tool that combines age-standardised death rates with simplex plots and Lexis plots to illustrate changes in the role that diseases play, differentiating between UCD, contributory cause in Part 2, and non-UCD in Part 1. The simplex plot assigns a colour based on the role composition of a disease by age and year. It then serves as a colour legend for the Lexis diagram to display role shifts in leading causes of death by age and period. Dementia and Alzheimer’s disease, ischemic heart disease, and cerebrovascular disease experienced temporal role changes in the death process across all countries studied. Age-dependent role changes were observed in particular in Denmark for pneumonia, alcohol-related diseases, and other infections. Some diseases exhibited contradictory trends in mortality rates from both the underlying and contributory cause perspectives, especially diabetes and chronic obstructive pulmonary disease (COPD) in Czechia, and sepsis and dementia in the USA and Denmark. By combining simplex and Lexis plots with mortality rates, we provided context for trends in mortality rates by underlying causes, which is in turn relevant for understanding cause of death dynamics. It is important to underscore the variations in death certification processes specific to each country.