The notion that cancer is predominantly a disease of old age is evolving. Recent analyses indicate that in the G20 group of industrialised nations, cancer rates are increasing more rapidly among younger populations compared to older ones. This trend has been confirmed by scientists at the American Cancer Society (ACS), who found that younger generations, particularly Gen X and Millennials, are more likely to develop certain types of cancer than Baby Boomers[1]. Half of the 34 types of cancer studied showed a “birth cohort effect,” indicating that these cancers are becoming more common among successively younger cohorts. For instance, the incidence rates of pancreatic and kidney cancer among those born in 1990 are two to three times higher than those born in 1955.
Generational Shifts in Cancer Risk
The findings, published in Lancet Public Health, suggest profound implications for future cancer care. The increasing incidence of cancer among younger populations necessitates rethinking screening programs and addressing fertility preservation during treatment. The rise in younger cancer patients poses a challenge as the disease evolves, making the goal of eradicating cancer more complex. Hyuna Sung, an epidemiologist at the ACS, and her colleagues analysed American cancer registry data involving over 23 million people diagnosed with 34 types of cancer between 2000 and 2019. They also examined registries recording over 7 million deaths from 24 types of cancer during the same period. Their research highlighted that several cancers, including colorectal, pancreatic, kidney, gallbladder, and testicular cancers, are on the rise among individuals under 50.
Lifestyle and Dietary Factors
Several modifiable lifestyle factors have been identified as contributing to the increased cancer risk among younger populations. These include:
- Dietary Patterns: High consumption of red and processed meats, sugary drinks, and a Westernised diet have been linked to an increased risk of early-onset colorectal cancer (EOCRC). Conversely, diets rich in fruits, vegetables, and fish are protective against colorectal cancer[2]. Increasing evidence points to hyperinsulinemia[3], chronic inflammation[4], and gut dysbiosis[5] as the plausible mechanisms linking diet and EOCRC. Various lifestyle, nutrition and supplement-based approaches can be utilised to restore eubiosis in the human gut, but this remains an area of interindividual diversity and accordingly has varied outcomes[6].
- Obesity and Metabolic Syndrome: Rising rates of obesity[7] and metabolic syndrome[8], often resulting from poor dietary habits and sedentary lifestyles, are significant risk factors for various cancers, including colorectal and breast cancer. Obesity is the second most common preventable cause of cancer and may soon overtake cigarette smoking as the most common preventable cause of cancer[9]. For nonsmokers, obesity is considered the single most common preventable cause of cancer, especially when accompanied by unhealthful nutrition and physical inactivity.
- Physical Inactivity: Sedentary behaviour is associated with an increased risk of several cancers, including colorectal cancer as well as cardiovascular disease and all cause mortality[10].
- Alcohol and Tobacco Use: Both alcohol consumption and smoking are established risk factors for multiple cancers, including colorectal and breast cancer. Recorded cases of cancer in under 50s between 1999 and 2019 soared by 79 per cent, according to scientists from the University of Edinburgh and the Zhejiang University School of Medicine in China[11]. Alcohol consumption and smoking were identified as the biggest risks. The University of Edinburgh-led team looked at the impact of 29 cancers on people aged between 14 and 49 years-old in more than 200 countries and regions.
- Environmental Factors: Emerging research suggests that environmental carcinogens, such as microplastics, may also play a role in the increasing cancer rates among younger populations. Microplastics, which have become prevalent since the 1960s, can disrupt the gut lining and potentially contribute to cancer risk[12]. Environmental pollution is one of the most serious challenges to health in the modern world. Pollutants alter immune responses and can provoke immunotoxicity.
- Screening and Prevention: In response to these trends, screening programs are being adjusted. For example, in the U.S., breast cancer screening is now recommended to start at age 40, a decade earlier than previous guidelines. However, experts are cautious about extending similar measures to colorectal cancer screening for younger individuals due to potential downsides like expense, radiation exposure, and false positives.
Conclusion
The shifting burden of cancer development towards younger populations underscores the need for closer policy attention and targeted prevention and lifestyle enhancement strategies. Addressing modifiable lifestyle factors, improving dietary habits[13], and enhancing screening programs are all going to be critical steps in mitigating the rising cancer risk among younger generations.
References:
[1] Sung H, Jiang C, Bandi P, Minihan A, Fidler-Benaoudia M, Islami F, Siegel RL, Jemal A. Differences in cancer rates among adults born between 1920 and 1990 in the USA: an analysis of population-based cancer registry data. Lancet Public Health. 2024 Aug;9(8):e583-e593.
[2] Zheng X, Hur J, Nguyen LH, Liu J, Song M, Wu K, Smith-Warner SA, Ogino S, Willett WC, Chan AT, Giovannucci E, Cao Y. Comprehensive Assessment of Diet Quality and Risk of Precursors of Early-Onset Colorectal Cancer. J Natl Cancer Inst. 2021 May 4;113(5):543-552.
[3] Chan AT, Giovannucci EL. Primary prevention of colorectal cancer. Gastroenterology. 2010;138(6):2029-2043 e2010
[4] Song M, Garrett WS, Chan AT. Nutrients, foods, and colorectal cancer prevention. Gastroenterology. 2015;148(6):1244-1260.e1216
[5] O’Keefe SJ. Diet, microorganisms and their metabolites, and colon cancer. Nat Rev Gastroenterol Hepatol. 2016;13(12):691-706
[6] Chowdhury M, Raj Chaudhary N, Kaur P, Goyal A, Sahu SK. Different Strategies Targeting Gut Microbiota for the Management of Several Disorders: A Sustainable Approach. Infect Disord Drug Targets. 2024;24(5):e160124225675.
[7] Lazarus E, Bays HE. Cancer and Obesity: An Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) 2022. Obes Pillars. 2022 Jul 5;3:100026.
[8] Jimba T, Kaneko H, Yano Y, Itoh H, Yotsumoto H, Seki H, Morita K, Kiriyama H, Kamon T, Fujiu K, Michihata N, Jo T, Takeda N, Morita H, Nishiyama A, Node K, Yasunaga H, Komuro I. Relation of the Metabolic Syndrome to Incident Colorectal Cancer in Young Adults Aged 20 to 49 Years. Am J Cardiol. 2021 Nov 1;158:132-138.
[9] Sung H., Siegel R.L., Torre L.A., Pearson-Stuttard J., Islami F., Fedewa S.A., et al. CA Cancer J Clin; 2018. Global patterns in excess body weight and the associated cancer burden.
[10] Zhao R, Bu W, Chen Y, Chen X. The Dose-Response Associations of Sedentary Time with Chronic Diseases and the Risk for All-Cause Mortality Affected by Different Health Status: A Systematic Review and Meta-Analysis. J Nutr Health Aging. 2020;24(1):63-70
[11] Jianhui Zhao, Liying Xu, Jing Sun, Mingyang Song, Lijuan Wang, Shuai Yuan, Yingshuang Zhu, Zhengwei Wan, Susanna Larsson, Konstantinos Tsilidis, Malcolm Dunlop, Harry Campbell, Igor Rudan, Peige Song, Evropi Theodoratou, Kefeng Ding, Xue Li – Global trends in incidence, death, burden and risk factors of early-onset cancer from 1990 to 2019: BMJ Oncology 2023;2:e000049.
[12] Li S, Keenan JI, Shaw IC, Frizelle FA. Could Microplastics Be a Driver for Early Onset Colorectal Cancer? Cancers (Basel). 2023 Jun 24;15(13):3323.
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