Why bowel cancer is increasing in younger adults

For many years, bowel cancer has been widely regarded as a condition that primarily affects older adults. However, this assumption is becoming increasingly outdated.

Across Australia, doctors are seeing more cases of bowel cancer in younger people. Among Australians aged 30 to 39, the incidence has tripled since 2000.

In my clinical practice, I am seeing more young patients diagnosed with bowel cancer, and many of them are diagnosed at later stages because their symptoms were initially dismissed or explained away.

As I often explain to patients, the idea that bowel cancer is only a disease of older adults is no longer accurate. We’re seeing more young patients diagnosed, often at later stages, because symptoms are dismissed or explained away.

Recognising symptoms and seeking medical advice early can make a significant difference.

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What symptoms of bowel cancer should younger adults watch for?

One of the challenges with bowel cancer in younger adults is that symptoms are often subtle at first. They can easily be mistaken for common digestive problems or lifestyle-related issues.

Some of the symptoms I most often see overlooked include:

• Changes in bowel habits, such as persistent diarrhoea or constipation
• Blood in the stool, which is often attributed to haemorrhoids
• Persistent abdominal pain or bloating
• Unexplained fatigue or iron deficiency
• Unexplained weight loss

Because bowel cancer is still widely associated with older age, both patients and clinicians may underestimate the significance of these symptoms in younger people.

However, persistent digestive changes should always be taken seriously. As I advise my patients, persistent changes in bowel habits, bleeding, or unexplained fatigue should always be investigated, regardless of age.

In general, any change in bowel habits that lasts longer than two to three weeks should be medically investigated.

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Why bowel cancer is increasing in younger adults

Researchers are still working to fully understand why early-onset bowel cancer is becoming more common. At present, there is unlikely to be a single cause.

Several factors have been associated with increased risk, including:

• Obesity
• Alcohol consumption
• Smoking
• Diets high in highly processed foods and red meat
• Disruption to the gut microbiome

Another factor we are seeing more frequently is the presence of sessile serrated polyps, a type of pre-cancerous growth in the bowel that appears to be increasing in younger patients. These growths may contribute to earlier disease development.

While genetics can play a role in certain cases, it does not appear to fully explain the broader rise in diagnoses among younger adults.

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Why younger adults are often diagnosed through symptoms rather than screening

Population screening programmes have helped reduce bowel cancer rates in older adults. In Australia, screening kits are routinely sent to people aged 50 to 74, with those aged 45 to 49 now able to opt in.

However, younger adults often fall outside routine screening programmes and therefore rely on symptoms being recognised and investigated.

Early detection dramatically improves outcomes. When bowel cancer is identified early, more than 90 percent of cases are treatable.

This is why persistent symptoms should never be dismissed simply because someone is considered “too young” for bowel cancer.

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When should you see a doctor about bowel symptoms?

If symptoms such as changes in bowel habits, blood in the stool, unexplained fatigue, or unexplained weight loss persist for more than a few weeks, it is important to seek medical advice.

Bowel cancer does not only affect older adults. Paying attention to changes in your body and seeking investigation when symptoms persist can play an important role in ensuring earlier diagnosis and treatment.

About the author

Associate Professor Viraj Kariyawasam is a senior gastroenterologist, hepatologist and endoscopist with academic appointments at Macquarie University and Western Sydney University. He specialises in inflammatory bowel disease (IBD), advanced therapeutic endoscopy, and cancer prevention. A/Prof Kariyawasam has extensive experience in gastrointestinal cancer screening and early detection, including colorectal cancer. He completed his medical training at the University of Colombo, obtained Fellowship with the Royal Australasian College of Physicians, and holds a PhD from the University of Sydney.