Which generations are at highest risk of cancer? New study looks at rates for 17 types

Researchers from the American Cancer Society (ACS) published a major observational study in the Lancet Public Health recently, with results that might give millennials another reason to think the boomer generation has had it better. They show that Generation Xers, born between 1965 and 1980, and millennials, born between the early 1980s and the late 1990s, have a higher risk of developing 17 different forms of cancer than the generations that preceded them. This risk is particularly high for breast cancer, pancreatic cancer and cancers of the digestive system, with mortality increasing in connection with cancers of the uterus, gallbladder and testicles, as well as colorectal cancers and liver cancers in women.“These findings add to the growing evidence of increased cancer risk in post-baby-boom generations,” observed lead study author Dr. Hyuna Sung. “Birth cohorts share unique social, economic, political and climatic environments that affect their exposure to cancer risk factors during the crucial years of their development. Although we have identified cancer trends associated with birth years, we do not yet have a clear explanation as to why these rates are increasing,” said the senior scientist at ACS in a statement released by the organization.To reach these conclusions, the researchers collated data on 23,654,000 American patients diagnosed with 34 types of cancer, as well as 7,348,137 deaths attributed to 25 types of cancer for patients aged between 25 and 84, during the period from Jan. 1, 2000, to Dec. 31, 2019. To compare cancer rates between generations, they calculated incidence and mortality rates by birth period, from 1920 to 1995, separated by five-year intervals.Incidence rates for eight of the 34 cancers analyzed increased progressively, year by year, for each birth cohort. “In particular, the incidence rate was about two to three times higher in the 1990 birth cohort than in the 1955 birth cohort for cancers of the small intestine, kidney, renal pelvis and pancreas, as well as for cancer of the liver and intrahepatic bile ducts in women,” the study states.In addition, the frequency of certain cancers tended to fall in people born before 1965, before gradually rising in those born after. These include estrogen receptor-positive breast cancer, colorectal cancer, cancer of the stomach (excluding cardia), uterus, gallbladder, ovary, testicles, anal cancer in men, and Kaposi's sarcoma, also in men.For all types of cancer, incidence rates among the cohort born between 1990 and 1995 were higher than those of previous generations, with increases ranging from 12% for ovarian cancer to 169% for uterine cancer compared to the cohorts with the lowest rates. What's more, mortality rates for some cancers have risen in tandem with their incidence. These include liver cancer in women only, uterine cancer, testicular cancer, gallbladder cancer and colorectal cancer.Future burden“Increasing incidence rates among younger cohorts indicate generational changes in cancer risk and often serve as an early indicator of the future burden of cancer in the country,” said study co-author Dr. Ahmedin Jemal, who fears that this burden could increase by, ”halting or reversing decades of progress against the disease. Our data underscore the critical need to identify and address underlying risk factors in Generation X populations and among millennials to develop prevention strategies,” added Dr. Jemal, who is also the senior vice-president of Health Equity Surveillance and Science at ACS. Some of these increases can be attributed to more frequent screening and advances in medical imaging. However, this does not explain the differences in incidence between generations born between 1965 and the end of the 1990s and earlier generations, according to the researchers, who point out in their study that “10 of the 17 cancers whose incidence is increasing in younger birth cohorts are obesity-related cancers—colorectal, kidney and renal pelvis, gallbladder and other bile ducts, corpus uteri, pancreas, gastric cardia, estrogen receptor-positive breast, ovary, myeloma, liver and intrahepatic bile ducts—suggesting a potential role for obesity in emerging cancer trends over recent decades.”Risk factorsAmong other plausible causes for the rising incidence rates of the 34 cancers they studied, the scientists mention that exposure to other putative risk factors such as unhealthy diet, sedentary lifestyle, altered sleep patterns and environmental chemicals influences cancer risk, “even though the prevalence of these factors remains poorly understood” among Gen-Xers and millennials. They add that certain dietary patterns (e.g., rich in saturated fats, refined grains, ultra-processed foods and sugar, as well as meat-based diets) and sedentary behaviours during adolescence and young adulthood have been associated with an increased risk of certain cancers, most notably colorectal and breast cancers.On a positive note, the researchers suggest that the stabilization of incidence rates for cancers of the liver and intrahepatic bile ducts, and the decrease for cancers of the mouth and pharynx in recent male birth cohorts, could be attributed, at least in part, to the reduction in alcohol consumption and smoking among men aged 18-to-25.In conclusion, the ACS research team points out that the results of their study have important implications for public health. “The increased risk of cancer in recent birth cohorts has already translated into increased cancer morbidity and mortality in young adults, posing unique challenges to the healthcare system and the community. It is essential to educate healthcare providers and the general public about the signs and symptoms of cancer in (this population) to enable early detection and treatment.”

Which generations are at highest risk of cancer? New study looks at rates for 17 types

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