Cancer incidence among young adults in the United States has become a public health concern. A new study uncovered 17 cancers becoming more common in Generation Xers and Millennials compared to older age groups. This trend raises concerns and questions about environmental and lifestyle factors that may contribute to the increasing cancer rates among young adults.
Generational Differences in Cancer Incidence
The study, published in the Lancet Public Health, examined cancer incidence among adults born between 1920 and 1990. It revealed a marked difference in the types and rates of cancer across generations. While cancer is generally associated with older men and women, this research suggests that some cancers are becoming more common in younger populations. There is also an increase in cancer-related deaths in people under 50 years old.
Dr. William Dahut, a chief scientific officer at the American Cancer Society and a co-author of the study, emphasized the findings’ urgency. He noted that some malignancies, such as uterine cancer, have seen a dramatic rise in incidence among individuals born in the 1990s compared to those born in the 1950s. More specifically, the incidence rate of uterine cancer is 169% higher in individuals born in the 1990s when they reach their 30s or 40s compared to people born in the 1950s at the same age.
What sets this study apart is its scope. The researchers analyzed data on 34 different types of cancer, identifying 17 that showed an increased incidence in younger adults under the age of 50. Additionally, the study found that five types of cancer have higher mortality rates among these younger cohorts.
What Types of Cancer Are Gen X and Millennials Most at Risk Of?
The 17 cancers with increasing incidence among young adults are:
1. Gastric Cardia Cancer
Gastric cancer occurs in two primary locations: the proximal gastric (cardia) and distal gastric (non-cardia). Cadia cancer occurs in the upper portion of the stomach, near where it connects to the esophagus.
While non-cardia cancer rates have declined in Western countries, cardia cancer has been on the rise since the 1970s. Non-cardia cancer is more widespread in developing countries, among Black populations, and in lower socioeconomic groups. Helicobacter pylori infection and diet are leading risk factors. In contrast, cardia cancer is more common in developed countries, among White populations, and higher socioeconomic groups. Gastroesophageal reflux disease (GERD) and the obesity epidemic are major risk factors.
2. Small Intestine Cancer
In recent years, the incidence of this relatively rare disease has been increasing among younger adults. Small intestine cancer, which affects the small bowel, is typically diagnosed late due to nonspecific symptoms such as abdominal pain, weight loss, and nausea. It accounts for 3% of gastrointestinal malignancies in the United States.
3. Estrogen Receptor-Positive Breast Cancer
This estrogen-driven disease is the most common type of breast cancer. The uptick in cases among younger women may be due to obesity, excessive alcohol consumption, and exposure to BPA or substances with estrogenic effects, among other risk factors. Please read Breast Cancer in Young People: Causes, Types, Consequences for more insights.
4. Ovarian Cancer
Doctors often diagnose ovarian cancer in its late stages, when it has spread or metastasized to the pelvis and/or abdomen. More women die from this malignancy than any other gynecologic cancer. The early symptoms mimicking those of common conditions are one of the main reasons for ovarian cancer’s late diagnosis.
The rise in incidence among younger women is concerning, as the earliest possible detection is often necessary for successful treatment.
5. Liver and Intrahepatic Bile Duct Cancer in Women
This cancer affects the liver and network of tubes carrying bile within the liver. It typically affects adults in their 70s, but the increasing rates among younger women may be related to factors like obesity and fatty liver disease. Unfortunately, 2 in 3 women in the United States are overweight or obese, and 1 in 3 persons have nonalcoholic fatty liver disease (NAFLD). NAFLD is the reason most women need a liver transplant.
6. Non-HPV-Associated Oral and Pharynx Cancers in Women
These malignancies affect the mouth and throat but are unrelated to the human papillomavirus (HPV). The surge in these cancers may be due to alcohol consumption and smoking. Tobacco and alcohol are Group 1 carcinogens. Smoking cigarettes, using chewing tobacco, and drinking alcoholic beverages can damage the cells lining the throat, affecting their ability to repair DNA. DNA damage has been long established as a causal factor for cancer occurrence.
7. Anal Cancer
Anal cancer comprises only 2.5% of all digestive tract cancers in the United States. However, the number of diagnoses in younger individuals is increasing, presumably due to changes in sexual behavior, HPV infections, and smoking habits.
8. Colon and Rectal Cancer
Colon and rectal (colorectal) cancer has been increasingly diagnosed in younger adults, a trend that has prompted changes in screening guidelines. Currently, researchers are unsure why more adults below 50 years old are developing colorectal cancer, but factors such as diet, obesity, and sedentary lifestyles may contribute to this rise.
9. Uterine Corpus Cancer
Uterine cancer has two types: uterine sarcoma (rare) and endometrial cancer (more common). The uterus is between a female’s urinary bladder anteriorly and the rectum posteriorly. Cancer in this organ can manifest as bleeding between periods or after menopause, which many mistake for common or benign conditions.
Having a high body mass index (BMI) or high body fat ratio, being postmenopausal or reaching menopause, having a thickened wall lining, early menstruation (age 12 or younger), never having children, having high blood pressure or high blood sugar, and a family history of uterine, ovarian, or bowel cancer are significant risk factors. Unfortunately, these issues are becoming more and more common in younger women.
10. Gallbladder and Other Biliary Cancers
Gallbladder cancer is rare in the United States. It affects only 2 in every 100,000 Americans.
This malignancy can be challenging to diagnose early, leading to poorer outcomes. The five-year survival rate for those with metastasized gallbladder cancer is 2%.
The rising cases in younger adults may be related to gallstones, which affect as much as 15% of the U.S. population. Obesity and chronic inflammation of the gallbladder are also suspected risk factors.
11. Kidney and Renal Pelvis Cancer
Kidney cancer, including renal cell carcinoma, is rare but on the rise among individuals aged 20 to 39. Risk factors include obesity, smoking, and high blood pressure, all of which have become more prevalent in younger populations.
12. Pancreatic Cancer
Pancreatic cancer is one of the world’s deadliest malignant diseases. Unlike other localized tumors with survival rates of over 90%, the prognosis over a five-year period for localized pancreatic cancer is 44%, while the prognosis for distant or metastasized tumors is 3%. The rising incidence in younger adults is alarming and may be due to obesity and chronic alcoholic pancreatitis.
13. Myeloma
Myeloma is a malignant tumor of the plasma cells in the bone marrow. This cancer is rare in young adults, but recent findings revealed that 10% of patients are under 50 and 2% are under 40 at the time of diagnosis.
The exact cause of myeloma in Gen X and Millennials is unknown. Researchers are looking into links between the disease, genetics, and environmental exposure to toxic substances, including pesticides and Agent Orange.
14. Non-Cardia Gastric Cancer
Unlike gastric cardia cancer, non-cardia gastric cancer affects the lower portion of the stomach. It has been decreasing in older adults but is on the rise in younger populations, potentially due to changes in diet and increased obesity rates.
15. Testicular Cancer
Testicular cancer is the second most common malignancy in males aged 20 to 39. The cause is unclear, but a tumor may develop due to undescended testicles, HIV infections, family history, and sex chromosome abnormalities.
16. Leukemia
Leukemia forms in the blood and bone marrow. Scientists broadly categorize it into several types, with acute lymphocytic leukemia (ALL) and acute myelocytic leukemia (AML) being more common among younger adults. The recent spike in leukemia cases among Gen Xers and Millennials has raised concerns and prompted further investigation.
Research suggests that environmental influences, including exposure to chemicals like benzene, ethylene oxide, and vinyl chloride, could be contributing factors. Individuals living near industrial sites or anyone exposed to radiation due to medical treatments or environmental disasters may also have an elevated risk.
17. Kaposi Sarcoma in Men
Kaposi sarcoma affects the blood and lymph vessels’ lining. It is more common in males than females, with most patients having one or more cancerous lesions on the legs, ankles, or feet.
This cancer is often associated with HIV/AIDS, but the rising incidence in younger men may also be linked to other immunosuppressive conditions.
The Study’s Methodology and Findings
The researchers analyzed data from over 23 million patients diagnosed with 34 different cancer types and over 7 million people who died from 25 different cancer types. The data, sourced from the U.S. National Center for Health Statistics and the North American Association of Central Cancer Registries, included adults aged 25 to 84 between January 2000 and December 2019.
The study calculated cancer incidence rates and death rates by birth year, dividing the data into five-year intervals from 1920 to 1990. The results were shocking: incidence rates for 8 of the 34 cancers examined increased with each successive generation born since 1920. Notably, the incidence rates for pancreatic, kidney, and small intestinal cancers were 2 to 3 times higher in those born in 1990 than those born in 1955. The rate of liver cancer among women also showed a similar jump.
Across various cancer types, the increased cancer incidence among people born in 1990 ranged from 12% higher for ovarian cancer to 169% higher for uterine corpus cancer when compared to the birth cohorts with the lowest incidence rates.
Obesity and Other Possible Causes of Rising Cancer Rates
The increasing incidence of certain cancers among young adults suggests that this rise may be linked to changes in the environment or lifestyle. Dr. Andrea Cercek, a gastrointestinal medical oncologist, noted that the rise in cases among young adults might be due to early exposure to environmental factors. This includes factors such as poor diet, minimal physical activity, obesity, and exposure to climate change.
Unsurprisingly, 10 of the 17 cancers with increasing incidence in younger adults are related to obesity. These include colon and rectal cancers, kidney and renal pelvis cancers, gallbladder and other biliary cancers, uterine corpus cancer, pancreatic cancer, estrogen receptor-positive breast cancer, cardia cancer, ovarian cancer, myeloma, and liver and bile duct cancers. For reference, 2 in 5 adults (42.4%) are obese, and 1 in 11 adults (9.2%) are severely obese. The link between obesity and cancer is well-documented, and this study suggests that the early onset of obesity in childhood or adolescence may support the higher cancer rates among young adults today.
Cancer development typically takes years, even decades, to manifest, indicating that the factors contributing to these cancers likely occurred during early life stages. Dr. Dahut emphasized that if Gen X and Millennials are developing cancer at an earlier age, their exposure to environmental or lifestyle risk factors likely took place during their teens or earlier.
Rising Cancer Mortality Rates in Younger Generations
The researchers also found that cancer-related deaths increased in Gen X and Millennials, which mirrors the rise in incidence rates. The numbers were particularly evident for liver cancer among women, uterine corpus, gallbladder, testicular, and colorectal cancers.
On a more positive note, malignancies related to HPV infections, such as cervical cancer, and those associated with tobacco use, such as lung cancer, are declining. This “accelerated downturn” in cervical cancer incidence demonstrates the effectiveness of HPV vaccination. Likewise, the drop in tobacco-related cancer corresponds with smoking cessation, as cigarettes continue to lose favor with Americans.
Implications for Public Health
Dr. Hyuna Sung, the study’s lead author and a senior principal scientist of surveillance and health equity science at the American Cancer Society, said their findings brought more attention to the heightened cancer risk in post-Baby Boomer generations. The study expands on previous research by highlighting a broader range of cancers that are rising in incidence among younger adults, particularly those associated with obesity. This trend is concerning, as it suggests early and prolonged exposure to risk factors, which may predispose Gen X, Millennials, and perhaps even Gen Alpha to cancer at younger ages compared to previous generations.
Dr. Sung pointed out that birth cohorts—groups of individuals classified by their birth year—experience unique social, economic, political, and environmental factors that shape their exposure to cancer risks during critical developmental periods. While the study has identified these troubling trends in cancer incidence and mortality among younger generations, the exact reasons for these increases remain obscure. There is an urgent need for further, more extensive research to better understand the environmental and lifestyle factors driving these changes.
Role of Early Screening and Diagnosis
One of the study’s main takeaways is the importance of routine screening and early detection in combating cancer progression among younger adults.
Dr. Ernest Hawk, chair of the Division of Cancer Prevention and Population Sciences at the University of Texas MD Anderson Cancer Center, suggested that obesity-related cancers are very concerning. This uptick in obesity rates among younger populations may be a major driver in the rising cancer incidence rates. Nonetheless, the availability of advanced diagnostic tools and the greater awareness among doctors and the public offer hope for early detection and improved outcomes.
Furthermore, in response to these trends, there has already been a shift toward earlier screening for certain cancers. For example, the U.S. Preventive Services Task Force (USPSTF) has lowered the recommended age for breast and colorectal cancer screening. In 2021, the USPSTF updated its guidelines to begin colorectal cancer screening at age 45 for average-risk adults, down from the previous suggestion of 50. Similarly, the USPSTF advises average-risk women to begin biennial mammograms for breast cancer at age 40, which is a decade earlier than the previous guideline.
These changes in risk-based screening signal the growing recognition of early cancer detection, particularly as it becomes more common in younger generations. Early detection, after all, helps improve survival rates, as stage 0 to 1 cancers are more responsive to treatment than advanced cancers.
The Bottom Line on Cancers Affecting Gen X and Millennials
Cancer’s frequency among Generation X (1965–1980) and Millennials (1981–1996) demands immediate attention from the scientific community, public health professionals, and lawmakers. Dr. Sung and his co-authors’ findings are a reminder that cancer does not discriminate by age; it affects younger populations, too, often more aggressively.
As we move forward, we must remain vigilant in monitoring cancer trends and adapting our detection and treatment strategies to address cancer’s evolving challenges. The study’s findings should serve as a call to action, rousing healthcare providers, researchers, policymakers, and the public to come together in the fight against cancer and to ensure that future generations are protected from this devastating disease.
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