Dr. Omar Marar, a board-certified, fellowship-trained colon and rectal surgeon, is among the specialists drawing attention to one of the most unsettling shifts in colorectal care: the disease is increasingly being diagnosed in adults decades younger than the traditional patient profile. For people in their thirties and forties, colorectal cancer is rarely on the radar, and that blind spot is part of what makes the trend so concerning.
For most of the last century, colorectal cancer was considered a disease of older adults. That picture has changed. According to the American Cancer Society, the share of new colorectal cancer cases among people younger than 55 nearly doubled, rising from about 11 percent in 1995 to 20 percent in 2019. Over the same period, a larger share of patients of all ages were diagnosed at an advanced stage, climbing from 52 percent in the mid-2000s to 60 percent in 2019.
A Shift Researchers Are Still Working to Explain
The rise in younger patients stands in sharp contrast to what has happened among older adults. As the National Cancer Institute has outlined in its overview of why colorectal cancer is rising among young adults, rates among people under 50 have climbed steadily since the 1990s even as rates in older adults dropped sharply, largely because of routine colonoscopy and lower smoking rates.
What is driving the increase is not yet settled. Inherited conditions such as Lynch syndrome account for only an estimated 10 to 20 percent of early-onset cases, which suggests that most of the change is coming from environmental and lifestyle factors rather than genetics. Researchers are studying diets high in processed meat and low in fruits and vegetables, rising rates of obesity, more sedentary routines, changes in the gut microbiome, and chronic inflammation. None of these has been proven to be a single cause, and the disease remains uncommon in younger adults overall. Even so, the generational pattern is clear enough that major medical organizations have changed how they approach prevention.
“The honest answer is that we do not yet know exactly why we are seeing more colorectal cancer in people in their thirties and forties,” says Dr. Omar Marar. “What we do know is that waiting for a perfect explanation is not a strategy. The practical response is earlier awareness, earlier evaluation, and screening on schedule.”
The Symptoms Younger Adults Tend to Dismiss
Because most adults under 45 are not yet eligible for routine screening, early-onset colorectal cancer is usually found only after symptoms appear. A study from Washington University School of Medicine, published in the Journal of the National Cancer Institute and based on more than 5,000 patients, identified four red-flag symptoms linked to early-onset colorectal cancer in the three months to two years before diagnosis. Risk climbed as symptoms accumulated: one symptom nearly doubled it, two raised it more than threefold, and three or more raised it more than sixfold.
- Rectal bleeding: Often assumed to be hemorrhoids, especially in younger people, which can delay a proper evaluation.
- Iron deficiency anemia: Sometimes found on routine bloodwork or experienced as unexplained fatigue, and a possible sign of slow blood loss in the digestive tract.
- Diarrhea and changes in bowel habits: Easy to blame on diet, stress, or a passing illness when they persist or keep coming back.
- Abdominal pain: A common complaint with many harmless causes, which is exactly why it is easy to overlook.
None of these symptoms means a person has cancer, and most have benign explanations. The concern is the delay. The same research team noted that many early-onset cases are diagnosed in emergency rooms, often after symptoms have been present for months.
“Rectal bleeding is never something I want a patient to explain away on their own,” Dr. Marar explains. “Most of the time the cause turns out to be benign, but the only way to know that is to be evaluated. A young patient who comes in early with a symptom gives us far more options than one who waits a year.”
Why Screening Now Starts at 45
In response to the shifting data, the U.S. Preventive Services Task Force updated its colorectal cancer screening recommendations to begin at age 45 for adults at average risk, five years earlier than its previous guidance. The American Cancer Society had already made the same change in 2018. Recommended options include colonoscopy every ten years as well as stool-based tests performed at shorter intervals, and any abnormal stool-based result calls for a follow-up colonoscopy.
There are important limits to keep in mind. Screening guidelines are designed for people without symptoms. Anyone who has symptoms needs a diagnostic evaluation, regardless of age. People with a family history of colorectal cancer or advanced polyps, inflammatory bowel disease, or a known hereditary syndrome may need to begin screening earlier than 45, and that decision should be made with a physician. For average-risk adults under 45, symptom awareness remains the main line of defense.
Practical Steps for Younger Adults
Specialists who focus on colorectal health tend to emphasize a few simple habits that make early detection more likely and may help lower overall risk:
- Know your family history: Share any history of colorectal cancer or advanced polyps among close relatives with your doctor, since it can change when screening should begin.
- Do not wait out persistent symptoms: Bleeding, ongoing changes in bowel habits, unexplained anemia, or recurring abdominal pain are reasons to schedule an appointment.
- Advocate for yourself: If symptoms continue after an initial explanation, it is reasonable to ask whether further evaluation is warranted.
- Support long-term digestive health: Regular physical activity, a fiber-rich diet, limiting processed meat, avoiding tobacco, and moderating alcohol are all associated with lower colorectal cancer risk, although no habit eliminates risk entirely.
“I want younger patients to hear two things at once,” says Dr. Marar. “Colorectal cancer is still uncommon at their age, so there is no reason for panic. But it is no longer rare enough to ignore, and when we find it early, treatment is usually far less extensive and outcomes are much better.”
Looking Ahead
The rise of colorectal cancer in younger adults is one of the clearest reminders that medical assumptions need to keep pace with the data. Until researchers pinpoint what is driving the trend, the most effective tools are already available: paying attention to the body’s warning signs, starting screening on time, and seeking care without hesitation when something feels off. For Dr. Omar Marar, closing the gap between the first symptom and the first appointment is where the greatest gains in early detection can be made.
About Dr. Omar Marar
A board-certified and fellowship-trained expert, Dr. Omar Marar specializes in advanced colorectal surgery at Valley Multi Specialty in Phoenix, Arizona. Having completed his training at the prestigious Thomas Jefferson University Hospital, he offers specialized management for complex conditions including colorectal malignancies, diverticulitis, and various anorectal pathologies. Beyond his clinical practice, Dr. Marar is a distinguished educator whose dedication to medical training was honored with the 2021 Spirit of Teaching Award. Through a combination of rigorous clinical expertise, scholarly research, and international humanitarian service, he remains committed to elevating surgical standards while ensuring empathetic, patient-centered care.