Researchers have published a new study offering a broad look at cancer rates in the United States.
The goal was to compare cancer incidence and mortality across different generations over time. The findings showed that Gen X and Millennials have incidence rates two to three times higher than those born in 1955, and they are also more likely to develop 17 different types of cancer.
The researchers pointed to factors such as environmental toxins, diet, and obesity as key contributors to this increase [1]. However, they noted that further research is still needed to better understand other factors behind the rising rates.
The Increase in Cancer Rates Among Gen X and Millennials
The same researchers carried out a similar study in 2019, which found increases in eight cancer types among more recent generations. However, until now, no study had considered both cancer incidence and mortality by birth year together. This new research aimed to close that major data gap [2].
The researchers noted that exposure to carcinogenic factors early in life influenced cancer incidence in people aged 50 and under [3]. They also suggested that more cases may emerge in the future as these younger groups age and carry their elevated risk into later life.
The 17 Types of Cancer
The study analyzed data from 23,654,000 individuals diagnosed with 34 different types of cancer. It also included records of 7,348,137 deaths across 25 cancers. The data came from people diagnosed or who died between 2000 and 2019. The findings showed increases in 17 of the 34 cancers among Gen X and Millennials:
small intestine
cardia gastric
ovary
estrogen receptor-positive breast
non-HPV-associated oral and pharynx (in females)
liver and intrahepatic bile duct (in females)
Kaposi sarcoma (in males)
anus (in males)
colorectal cancer
endometrial cancer
gallbladder and other biliary
pancreas
kidney and renal pelvis
myeloma
non-cardia gastric
leukemia
Increase in Cancer Incidence and Mortality Among Gen X and Millennials
The increase in cancer incidence was especially notable in cancers of the pancreas, kidneys, renal pelvis, thyroid, and small intestine. The researchers also found rising mortality rates in five cancer types: liver, endometrial, gallbladder, testicular, and colorectal cancers.
These results are concerning, as they suggest the higher cancer risk among Gen X and Millennials is not simply due to improved detection or more frequent diagnoses. Instead, they point to a real and worrying rise in risk at the population level. New cases are increasing at a pace that outstrips gains made in treatment.
The Causes Behind the Rise in Cancer Incidence
The study set out to gather new data on cancer incidence, but it does not identify specific causes. However, researchers point to several known contributing factors. Obesity was highlighted as a major factor, linked to 10 of the 17 cancers identified in the study.
Obesity rates have generally risen across all age groups since the 1970s, with the sharpest increase seen in those aged 2 to 19. Other factors mentioned include environmental pollutants, disrupted sleep patterns, and a sedentary lifestyle.
Gut Microbiome and Diet-Related Factors
The rise in cancer incidence has also been associated with the modern Western diet [4]. These foods are often highly processed and rich in sugar, saturated fats, and refined grains. However, heavily processed foods are linked not only to weight gain. They have also been directly associated with a higher risk of colorectal and breast cancers.
Since some cancers affecting the digestive system are not explained by obesity alone, researchers suggest changes in the gut microbiome may play a role. They note that gut microbiomes are strongly influenced by Western diets as well as antibiotic use.
It’s Not All Bad News
Overall, the study found a clear rise in incidence across 17 cancers in Gen X and Millennials. Still, the findings are not entirely negative, as some cancer types are in decline. Women born around 1990 are now less likely to develop cervical cancer, largely because HPV vaccines were introduced in the U.S. when they were around 16 years old.
Declining smoking rates have also led to reductions in cancers of the esophagus, larynx, and lungs. And while overall incidence has increased in Gen X and Millennials, improved early detection has contributed to a drop in mortality rates.
The Bottom Line
Our understanding of cancer and its causes continues to expand alongside advances in treatment. Yet many health conditions that appear later in life can often be traced back to factors in earlier years.
The study highlighted an increase in 17 types of cancer among Gen X and Millennials, raising questions about modern influences affecting younger generations. Still, it is not entirely bleak. Despite the overall rise in incidence, certain lifestyle changes have contributed to declines in some cancers.