Decline in Bowel Cancer Among Adults Over 50 Contrasts with Rising Rates in Younger Adults

Bowel cancer remains one of the most common types of cancer in Australia, accounting for a significant portion of cancer diagnoses and deaths each year. Historically, the majority of cases occur in adults over 50, and recent national screening programs have contributed to a decline in incidence within this age group. Since 2006, Australia has implemented a population-based screening initiative, where adults aged 50 to 74 receive a mailed kit every two years. This simple test detects hidden blood in stool, serving as an early warning sign of potential cancer or precancerous changes, thereby enabling earlier diagnosis and improving survival rates. Despite its proven effectiveness, participation remains suboptimal at approximately 40%, and increasing engagement could further reduce bowel cancer rates.

However, while older populations are seeing a decline in new cases, worrying trends have emerged among younger adults. Recent studies indicate an increase in bowel and rectal cancers in individuals under 50, with data suggesting that those born in the 1990s face two to three times higher risk compared to those born in the 1950s. This rise in early-onset bowel cancer has been observed internationally, with Australia now having one of the highest rates of young-onset cases globally.

The precise causes of this upward trend are still unclear. Researchers are investigating various potential factors, including diet, lifestyle, obesity, and red meat consumption. The challenge lies in the complexity of studying diet over long periods and conducting randomized trials. Emerging hypotheses point toward the role of childhood infections—particularly certain strains of E. coli—and alterations in the gut microbiome as possible contributors to early DNA changes that increase cancer risk later in life.

To reduce individual risk, experts recommend vigilance for symptoms like blood in the stool or changes in bowel habits and prompt medical consultations. While screening for bowel cancer begins at age 50, individuals aged 45-49 can now request screening kits. Increasing participation in screening programs is crucial to reducing the broader burden of bowel cancer in Australia, especially given the rising incidence among younger individuals.

Source: [https://medicalxpress.com/news/2025-06-bowel-cancer-declining-people-younger.html]