Overall colon cancer rates in the United States have declined steadily over the last 30 years. But rates of colon cancer in young adults have risen dramatically during this period for unknown reasons.
Colon or rectal cancer that develops in people under age 50 is often referred to as early-onset colorectal cancer. Rates of early-onset colorectal cancer in the United States have nearly doubled since the early 1990s and similar trends have been observed in many other countries.
The incidence rate of early-onset colorectal cancer in the United States was 4.8 cases per 100,000 people in 1994, but by 2021, it rose to 10.1 per 100,000 people.
Researchers have proposed several theories about why rates continue to increase in young adults. One theory is that a combination of factors likely contribute, such as dietary changes, increased obesity rates, and lower physical activity.
Keep reading to learn more about the potential reasons why colon cancer rates are on the rise in young adults.
What is potentially causing the rise of colon cancer in young adults?
Colon cancer is the leading cause of cancer death in adults ages 20 to 49 and rates are continuing to increase.
People with early-onset colorectal cancer tend to have more aggressive and more advanced cancer than older adults.
Currently, early-onset colorectal cancer makes up about 10% of new cases of colorectal cancer in the United States, but it’s estimated that this could increase to 25% over the next 10 years.
Here’s a look at how rates have changed since 1994 based on the National Cancer Institute’s SEER data :
| Age | 1994 rate (per 100,000) | 2021 rate (per 100,000) | Change |
|---|
| 15 to 39 | 2.4 | 5.8 | 142% increase |
|---|
| 40 to 64 | 49.1 | 50.9 | 4% increase |
|---|
| 65 to 74 | 228.6 | 109 | 110% decrease |
|---|
It’s not clear why rates are rising for young adults, but most cases of colon cancer aren’t linked to a family history .
Sporadic versus inherited colon cancer
Colon cancer is called sporadic when it develops in people without inherited gene mutations linked to cancer.
About 70% of colorectal cancers are sporadic, about 25% are caused by inherited genes, and about 5% are linked to inherited syndromes such as Lynch syndrome or familial adenomatous polyposis .
Most colorectal cancer in young people seems to be sporadic. Multiple factors linked to lifestyle changes over the past 30 years likely play a role.
Obesity is one of the most established risk factors for colorectal cancer. For example, in a 2018 study , researchers found that women with obesity had a 20% higher risk of early-onset colorectal cancer than women without obesity.
In a study from 2017 , researchers found that excess body fat in early life, defined as under the age of 30, was associated with an increased risk of colon cancer. It’s thought that inflammatory molecules produced by fat tissue called cytokines and chronically high insulin levels could contribute to cancerous changes in the colon.
Diabetes has also been consistently found as a risk factor for colorectal cancer and likely contributes to the development of early-onset colorectal cancer.
In a 2020 study , researchers found that men and women with diabetes reached the same level of risk for colorectal cancer at age 45 as people without diabetes at age 50.
Do some people have a greater risk for developing colon cancer at a younger age?
Researchers are still examining potential risk factors for developing early-onset colorectal cancer. Many possible risk factors have been identified, but the level of evidence to support each varies.
Some of the major risk factors may include:
| Risk factor | Level of evidence |
|---|
| Excess body weight | High |
| High body fat at an early age | High |
| Diabetes | High |
| Smoking | Likely |
| Alcohol use | Likely |
| Low levels of physical activity | Likely |
Other risk factors for early-onset colorectal cancer may include:
Diets high in the following seem to be associated with a lower risk of colorectal cancer:
What are the symptoms of colon cancer in young adults?
Colorectal cancer symptoms often mimic those of other gastrointestinal conditions such as Crohn’s disease or irritable bowel syndrome . However, as the condition progresses, symptoms worsen.
Common early signs and symptoms can include:
Other symptoms can include:
If the cancer spreads to other locations, it may cause:
Can colon cancer be prevented?
A combination of your genetics and your lifestyle habits can contribute to developing colon cancer. Even though you can’t always prevent colon cancer , some ways you might be able to lower your risk include:
- increasing your physical activity levels
- maintaining a healthy weight for your body
- eating a diet low in animal fats and high in:
- whole grains
- fruits
- vegetables
- limiting alcohol consumption
- avoiding tobacco
The CDC recommends that people get regular screenings for colon cancer .
At what age and how often should young adults be screened for colon cancer?
The U.S. Preventative Services Task Force and the American Cancer Society have decreased the recommended age to start screening from age 50 to 45 . If you have a family history, your doctor may want to screen you starting at age 40 or 10 years before your earliest family member was diagnosed.
Takeaway
Colon cancer rates are continuing to rise in young adults even though overall colon cancer rates are continuing to decline.
It’s not entirely clear what’s causing this but contributing factors may include increased obesity, dietary changes, and lower levels of physical activity.
It’s important to visit your doctor if you develop unexplained gastrointestinal symptoms such as pain or blood in your stool without a known cause. Colon cancer has the best outcomes when it’s caught in the early stages.
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