Abstract Increasing incidence rates of early-onset colorectal cancer (eoCRC, 50 years) have been reported across multiple countries. We investigated long-term cancer incidence data (from 1995 or earlier) from Australia, Canada, England, and the U.S, separately by sex. Estimated annual percentage change (EAPC) and age-period-cohort (APC) models were used to assess trends by country and sex. All countries showed increasing eoCRC incidence in successive birth cohorts since 1960, with those born in the 1990s facing at least five-fold higher risks than those born in the 1960s. Cohort effects were observed across all countries, with sharper increases at younger ages. Over the most recent decade, EAPC ranged from 3.7% in Canada to 6.0% in England, with steep rises before age of 40. The emergence of these trends from ages 20–29 suggests contributing factors may originate early in life and may reflect exposures whose effect begin in youth and accumulate throughout the lifespan.
Downham et al. (2025) studied this question.