# Trends and the Age–Period–Cohort Effects on Mortality of Breast Cancer Among Iranian Women from 1990 to 2021

## TL;DR

This study analyzed breast cancer mortality trends in Iranian women from 1990 to 2021, finding an overall increase in crude rates but a decline in age-adjusted rates.

## Contribution

The study provides new insights into age-period-cohort effects on breast cancer mortality in Iran using GBD data and APC modeling.

## Key findings

- Crude mortality rates increased by 0.913% annually, while age-adjusted rates decreased by 0.384%.
- Age and period effects showed increasing trends, while cohort effects showed a consistent decline.
- The period effect rose from 1992 to 2021, and the cohort effect decreased from earlier to later birth cohorts.

## Abstract

The Eastern Mediterranean Region, including Iran, has the highest incidence and mortality of breast cancer (BC) in women. This study examined changes in BC mortality trends among Iranian women by age period cohort (APC) from 1990 to 2021.

BC deaths and population by age (1990‒2021) were collected from the 2021 Global Burden of Disease (GBD) study and the average annual percentage change (AAPC) and relative risks (RRs) analyzed by joinpoint regression and the APC model.

From 1990 to 2021, the crude and adjusted BC mortality rates showed an increasing (AAPC=0.913%; 95% CI: 0.436%, 1.393%) and decreasing (AAPC=-0.384%, 95% CI: -0.759%, -0.008%) trend, respectively. The APC analysis exhibited an increasing trend in age effect except in the 60‒74 and 80‒84 age group. The period effect also presented an increasing trend from 1992 (RR=0.716; 95% CI: 0.697, 0.734) to 2021 (RR=1.410; 95% CI: 1.381, 1.441). Additionally, the cohort effect illustrated that the mortality rate decreased consistently from the earlier birth cohort to the later birth cohort (Coef=1.017 in<1901 cohort versus Coef=-0.928 in 2002-2006 cohort).

Between 1990 and 2021, BC mortality in Iran showed an increase in crude rates but a decline in age-adjusted rates, with rising age and period effects and a decreasing cohort effect. These patterns may reflect improvements in early detection and treatment alongside demographic shifts, highlighting the need for continued monitoring to guide control strategies.