Colorectal cancer trends in Iran: An age-period-cohort analysis of incidence and mortality and trends in key risk factors.

BACKGROUND AND PURPOSE: Colorectal cancer (CRC) represents a growing public health challenge in Iran, with a marked upward trajectory in recent decades. This study aimed to analyze temporal trends in CRC incidence and mortality along with associated risk factors, across Iran from 1992 to 2021 using age-period-cohort (APC) modeling.

METHODS

Data were obtained from the Global Burden of Disease (GBD) study. APC modeling was employed to assess independent temporal effects on CRC trends, complemented by Lee-Carter models to improve interpretability and address identifiability constraints. Joinpoint regression was used to detect significant shifts in age-standardized disability-adjusted life years (DALYs) trends over time.

RESULTS

From 1992 to 2021, the age-standardized incidence rate of CRC in Iran increased substantially by 45.1%, whereas mortality remained relatively stable with only a minimal increase of 3.66% and DALYs essentially unchanged (+0.46%), resulting in a widening incidence-mortality gap suggestive of improved survival. A uniform upward shift in incidence curves emerged after 2000 across all age groups, coinciding with rising metabolic risk factors-particularly high BMI and elevated fasting glucose.

CONCLUSION

The marked increase in colorectal cancer (CRC) incidence in Iran appears to be largely driven by epidemiological transition and the growing prevalence of modifiable metabolic risk factors, particularly obesity and physical inactivity. The expanding gap between the rising incidence and relatively stable mortality rates may indicate modest improvements in survival, likely attributable to better access to diagnostic and therapeutic services rather than effective primary prevention. These findings highlight the urgent need to implement organized screening programs and develop targeted interventions aimed at reducing metabolic risk factors.