A Study Of 96,000 People Reveals A Concerning Trend For Colorectal Cancer
For decades, colorectal cancer was considered a disease of older adults. This was something to start thinking about at 50, when routine screening begins. But now, colorectal cancer is now the leading cause of cancer death1 in U.S.adults under 50, with cases rising 3% every year in adults aged 20 to 49, even as rates fall in adults 65 and older.
A large new study out of Switzerland further confirms this troubling trend. Researchers analyzed more than 96,000 colorectal cancer cases over four decades and found that while overall colorectal cancer rates have declined in adults over 50, cases in adults under 50 have continued to climb.
Here's what you need to know, and what you can do to lower your risk.
About the study
The Swiss study drew on national cancer registry data spanning roughly 40 years, making it one of the most comprehensive looks at colorectal cancer trends across generations. Researchers compared incidence rates across different age groups over time, tracking how those patterns changed.
The goal was to understand whether the rise in younger-adult cases was a new development or a long-standing trend.
What they found was that the increase in adults under 50 has been building steadily for decades, even as public health efforts to screen and prevent colorectal cancer have successfully brought rates down in older adults.
Researchers also found that survival has improved over the past several decades, suggesting advances in detection and treatment have made a difference. However, those gains appeared to level off among younger women after 2010, highlighting that progress has not been uniform across all groups.
Younger adults are being diagnosed later & at more advanced stages
It's also important to note that those cases are being caught late. When colorectal cancer is found early, treatment is far more likely to be successful. When it's caught at stage IV, after it has spread to other organs like the liver or lungs, it becomes much harder to treat.
The fact that nearly 1 in 4 younger patients were already at stage IV at diagnosis points to a real gap. Many younger adults aren't being screened (probably because screening recommendations for the general population start at age 45). And symptoms are often nondescript or may be accounted for other digestive issues. These symptoms include:
- Rectal bleeding: The most common symptom, showing up in 45% of early-onset cases in one analysis — and associated with at least a fivefold higher risk of colorectal cancer. It's frequently dismissed as hemorrhoids, but persistent or unexplained bleeding always warrants a conversation with your doctor
- Abdominal pain: Present in about 40% of cases; pain that is persistent or getting worse without a clear cause deserves attention
- Changes in bowel habits: Reported in 27% of cases — this includes new-onset constipation, diarrhea, narrowing of stool, or a persistent feeling that your bowel isn't fully emptying
- Iron-deficiency anemia: Unexplained low iron, especially without an obvious dietary reason, can be a sign of slow internal bleeding from a colorectal tumor
- Unintentional weight loss or fatigue: When these show up alongside other GI symptoms, they're worth investigating
A systematic review2 found that the average time from when symptoms first appeared to when a diagnosis was made was 6.4 months. In adolescents and young adults specifically, one study3 found that gap stretched to nearly 14 months.
Why colorectal cancer is rising in younger adults
Researchers don't have one single explanation, but the evidence points to a mix of lifestyle and environmental changes that have shifted significantly over the past few decades, particularly during childhood and adolescence, when the body is still developing. A large review4 identified several likely contributing factors like a Western-style diet heavy in processed foods and low in fiber, rising obesity rates, physical inactivity, and antibiotic use, especially early in life.
A 2025 review5 found that the rise in early-onset colorectal cancer closely tracks the surge in obesity and type 2 diabetes among younger people, with both conditions linked to the disease through shared pathways involving insulin resistance and chronic, low-grade inflammation.
These factors can disrupt the gut microbiome (the community of bacteria living in your digestive tract), affect how your immune system functions, and trigger changes in colorectal cells over time.
How to lower your risk and when to get screened
Current U.S. guidelines recommend that average-risk adults start colorectal cancer screening at age 45, a threshold the American Cancer Society lowered from 50 in response to rising rates in younger adults. These five takeaways from the updated ACS guidelines are worth reading for a full breakdown of what that means in practice.
Implementing certain diet and lifestyle changes can help reduce your risk for developing colorectal cancer. Here are a few habits that can have the biggest impact:
- Eat more fiber: Vegetables, legumes, whole grains, and fruit support a healthy gut and are consistently linked to lower colorectal cancer risk. These three food groups are a good place to start
- Limit processed and red meats: Processed meats are classified as a Group 1 carcinogen by the World Health Organization — meaning there's strong evidence they cause cancer. Cutting back is one of the most evidence-backed dietary changes you can make
- Cut back on sugary drinks: Given the research linking sugar-sweetened beverages6 to significantly higher early-onset risk, swapping them for water, coffee, or milk is a high-impact change
- Maintain a healthy weight: Excess body weight is one of the most consistently identified risk factors for early-onset colorectal cancer. Researchers examining 36 cancer types found excess weight among the top modifiable risk factors across the board
- Move regularly: Physical inactivity has been linked to increased risk; regular exercise supports metabolic health, reduces inflammation, and benefits gut function
When to talk to a doctor
If you're under 50 and experiencing any of the symptoms above, especially rectal bleeding, persistent abdominal pain, or unexplained changes in bowel habits, don't wait. Bring it up at your next appointment, or schedule one sooner if symptoms are worsening.
If you have a first-degree relative (parent, sibling, or child) who was diagnosed with colorectal cancer or polyps, particularly before age 60, ask your doctor whether earlier screening makes sense for you.
The takeaway
Colorectal cancer is no longer just an older adult's concern. Rates are rising in younger people even as they fall in older generations, and too many younger adults are being diagnosed late, when the disease is harder to treat. Knowing the warning signs, paying attention to modifiable risk factors, and speaking up when something feels off are the most practical tools younger adults have right now.