A new study led by researchers at the American Cancer Society indicates that Generation X and Millennials in the United States face a higher risk of developing several types of cancer compared to older generations.
To compare cancer rates across different generations, the study calculated incidence and mortality rate ratios for specific birth cohorts, adjusting for age and period effects. The cohorts were defined by five-year birth intervals, ranging from 1920 to 1990.
The findings suggest that cancer incidence rates have risen in successively younger generations for 17 of the 34 cancer types studied, including breast, pancreatic, and gastric cancers.
“Birth cohorts, groups of people classified by their birth year, share unique social, economic, political, and climate environments, which affect their exposure to cancer risk factors during their crucial developmental years. Although we have identified cancer trends associated with birth years, we don’t yet have a clear explanation for why these rates are rising.”
The study found that mortality trends also increased in conjunction with the incidence of liver (female only), uterine corpus, gallbladder, testicular, and colorectal cancers.
The analysis revealed that the incidence rate for eight of the 34 cancers was approximately two to three times higher in the 1990 birth cohort than in the 1955 birth cohort.
Some of the cancers that have a higher incident rate for the 1990 birth cohort compared to the 1955 birth cohort include pancreatic, kidney, and small intestinal cancers in both males and females and liver cancer in females.
Incidence rates also increased in younger cohorts for nine other cancers, including estrogen-receptor-positive breast cancer, uterine corpus cancer, colorectal cancer, non-cardia gastric cancer, gallbladder cancer, ovarian cancer, testicular cancer, anal cancer in male individuals, and Kaposi sarcoma in male individuals.
Ahmedin Jemal, senior vice president of surveillance and health equity science at the American Cancer Society, said that “without effective population-level interventions … an overall increase in cancer burden could occur in the future, halting or reversing decades of progress against the disease.”
“The data highlights the critical need to identify and address underlying risk factors in Gen X and Millennial populations to inform prevention strategies,” Jemal said.
The study suggests that the increase in cancer incidence among younger generations may reflect changes in exposures during early life or young adulthood.
These include potential carcinogenic factors related to lifestyle, diet, obesity, and environmental exposures. Ten of the 17 cancers with increasing incidence are obesity-related, indicating a potential link between obesity and emerging cancer trends.
The study’s authors call for more research to investigate the mechanisms contributing to heightened cancer incidence and the development of interventions that align with the social and cultural contexts of younger generations.
They emphasize that effective prevention strategies are essential to mitigating the future cancer burden.