Incidence rate ratios increased with each successive birth cohort born since 1920 for eight of 34 cancers
By Elana Gotkine HealthDay Reporter
THURSDAY, Aug. 1, 2024 (HealthDay News) — Younger birth cohorts have an increased incidence of many common cancer types, according to a study published in the August issue of The Lancet Public Health.
Hyuna Sung, Ph.D., from the American Cancer Society in Atlanta, and colleagues obtained incidence data for 34 types of cancer and mortality data for 25 types of cancer for individuals aged 25 to 84 years for Jan. 1, 2000, to Dec. 31, 2019. Birth cohort-specific incidence rate ratios (IRRs) and mortality rate ratios (MRRs) were calculated by nominal birth cohorts from 1920 to 1990, adjusted for age and birth effects.
The researchers found that with each successive birth cohort since 1920, the IRRs increased for eight of 34 cancers. The incidence rate was about two to three times higher in the 1990 birth cohort versus the 1955 birth cohort for small intestine, kidney and renal pelvis, and pancreatic cancers in both men and women (IRRs, 3.56, 2.92, and 2.61, respectively) and for liver and intrahepatic bile duct cancer for women (IRR, 2.05). For nine of the remaining cancers, the IRRs increased in younger cohorts after a decline in older birth cohorts. In successively younger birth cohorts, the MRRs increased alongside IRRs for liver and intrahepatic bile duct cancer in female individuals and in uterine corpus, gallbladder and other biliary, testicular, and colorectal cancers. For most cancer types, MRRs declined or stabilized in younger birth cohorts.
“Our findings highlight the importance of early lifetime exposures and highlight crucial opportunities to prevent a substantial fraction of cancer occurrence through modification of environmental and lifestyle risk factors,” the authors write.
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