Burden of 292 causes of death and life expectancy decomposition in Iran, 1990–2023: a systematic analysis for the Global Burden of Disease Study 2023

BACKGROUND: Better evaluation of the contribution of the main diseases, injuries, and risk factors for mortality and life expectancy is crucial for more efficient policy making at the national and subnational levels in Iran. The aim of this study is to assess the effect of emerging causes of mortality on health, specifically COVID-19, which can help policy makers implement preventive measures in similar situations. METHODS: In this systematic analysis of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2023, we present estimates of cause-specific mortality at the national and subnational levels in Iran from 1990 to 2023. New to this iteration of GBD, we present a decomposition analysis of the contribution of specific causes of death to net gain or loss in life expectancy across 31 provinces of Iran. We used an array of data sources including censuses, vital registration, and surveys for national and subnational estimates. FINDINGS: The two leading causes of death in Iran were ischaemic heart disease and stroke in both 1990 and 2019. However, in 2020 and 2021, the COVID-19 pandemic displaced the leading causes of death, ranking first with age-standardised mortality rates of 286·2 deaths (95% uncertainty interval 267·9-310·5) per 100 000 in 2020 and 250·0 deaths (233·2-272·5) per 100 000 in 2021. COVID-19 ranked second and tenth in 2022 and 2023, respectively. Life expectancy at birth for both sexes combined declined from 78·0 years (77·7-78·1) in 2019 to 74·3 years (74·0-74·4) in 2020. It steadily recovered to 78·8 years (78·5-79·2) in 2023. COVID-19 was the main cause of loss in life expectancy, by 4·19 years, between 2019 and 2020. There was a net gain of 12·4 years in life expectancy in Iran from 1990 to 2023. The net gain at the national level can be mostly attributed to reduced mortality from ischaemic heart disease (2·61 years), stroke (1·63 years), neonatal disorders (1·26 years), transport injuries (0·88 years), and neoplasms (0·64 years). The decline in mortality rates of major causes continued to 2023 despite the pandemic. An exception was Alzheimer's disease, which showed a 4·0% increase in rate between 2019 and 2023 and led to a net loss of 0·04 years in life expectancy since 1990. Diabetes led to a net loss of 0·09 years since 1990. There were variations between provinces in terms of age-standardised rates and the net change in life expectancy before and after the COVID-19 pandemic. INTERPRETATION: The COVID-19 pandemic disrupted the rising trend of life expectancy in Iran, varying across provinces. Findings show that the health-care infrastructure and policies in Iran were not efficient in controlling the pandemic in 2020 and 2021, mainly due to inadequate vaccination coverage and timeliness, specifically for vulnerable subgroups. Sanctions may have aggravated the effect of COVID-19 on loss in life expectancy of Iranians. Despite the pandemic, the declining trend in age-standardised rates for top causes of mortality has continued to 2023, leading to a full recovery of life expectancy and underscoring the ultimate resilience of Iran's health system. FUNDING: Gates Foundation.