Extended abstract
Introduction
Life expectancy at birth is a key indicator of human development and health system efficiency, reflecting the overall social and economic conditions of a population. Over the past decades, Iran, similar to many countries, has experienced a remarkable improvement in life expectancy - from about 25 years in the early 20th century to more than 76 years in recent years- mainly due to better health services, lower infant mortality, and control of infectious diseases. However, the epidemiological transition has led to a shift in mortality patterns toward non-communicable diseases such as cardiovascular diseases, cancers, and diabetes.
Given the significant effects of the COVID-19 pandemic on mortality patterns, analyzing how the elimination of major causes of death affects life expectancy has become increasingly important. Therefore, this study aims to estimate the multiple-decrement life tables for Iran from 2011 to 2021 and to forecast them for 2026, providing a comprehensive view of how major causes of death contribute to changes in life expectancy.
Method and Data
This descriptive-analytical study relies on secondary data analysis using information from the Global Burden of Disease (2021). The dataset includes the number of deaths by age, sex, and cause of death for the years 2011–2021. The quality and completeness of death registration were assessed using the Bennett–Horiuchi method.
After data correction, standard life tables were constructed separately for men and women. Age-specific mortality rates for 2026 were projected using the Lee - Carter model - a stochastic two-factor model widely used in actuarial and demographic forecasting - implemented in R software. Then, using the MORTPAK package, both standard and multiple-decrement life tables were computed.
Six major causes of death were included: cardiovascular diseases, cancers, diabetes and kidney diseases, respiratory infections and tuberculosis, chronic respiratory diseases, and traffic accidents. For each, separate life tables were generated to evaluate the potential increase in life expectancy under a hypothetical elimination of that specific cause.
Findings
The results showed that in 2011 and 2019, cardiovascular diseases were the most important cause of death for Iranian men and women, accounting for between 40 and 50 percent of all deaths among men and women. After that, cancers and traffic accidents accounted for the largest share among men, and cancers and diabetes accounted for the largest share among women. In 2021, under the influence of the Covid-19 pandemic, respiratory infections and tuberculosis took the first place among the causes of death, and the share of cardiovascular diseases decreased to 26 percent in men and 35 percent in women. The forecast for 2026 shows that with the control of the pandemic, cardiovascular diseases, cancers, and diabetes will again be the three leading causes of death in both sexes.
Based on life table calculations, life expectancy at birth for men has increased from 73.45 years in 2011 to 75.93 in 2019 and 77.17 in 2026. For women, it has also increased from 76.84 to 78.45 and then 79.70 years, respectively. The temporary decrease in life expectancy in 2021 (due to Covid-19) has been calculated to be 71.13 years for men and 75.94 years for women.
In the multi-decrement life tables, the largest increase in life expectancy was observed due to the elimination of cardiovascular diseases: in 2021, the elimination of this cause increased life expectancy by 3.4 years for men and 4.4 years for women. The share of cancers and diabetes in the increase in life expectancy has also been growing, especially in recent years, while the share of traffic accidents has continuously decreased. Also, in 2021, the simultaneous elimination of the three major causes of death (cardiovascular diseases, cancers and traffic accidents) could have increased life expectancy at birth by 9.8 years for men and 9.9 years for women.
The age pattern of causes of death showed that deaths from heart disease and diabetes were mainly concentrated in those over 55 years of age, while deaths from traffic accidents accounted for the largest share in the 20-40 age group. The sex ratio of deaths from cancer was also higher than 100 in all years, indicating that more men died than women.
Discussion and Conclusion
Iran has clearly transitioned to the stage of predominance of non-communicable diseases within the epidemiological transition framework. Although eliminating cardiovascular diseases yields the highest potential improvement in life expectancy, its declining contribution during the past decade suggests that Iran has entered the fourth phase—characterized by delayed deaths from chronic conditions. Conversely, the growing role of cancers and diabetes underscores the need for more effective prevention and management of chronic diseases.
Forecasting results indicate that life expectancy in Iran will continue to increase