July 8, 2024
July 8, 2024

Why are Colorectal Cancer Rates Rising Among Younger Adults?

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Why are Colorectal Cancer Rates Rising Among Younger Adults?

Colorectal cancer (CRC) rates have dramatically increased in younger adults in recent years. These cases are commonly referred to as early-onset CRC or young-onset CRC (YO-CRC). The reasons behind this increase are not fully known, though scientists have offered several hypotheses. Naturally, this causes health-conscious individuals within this age group to want to learn more about the risks of CRC and implement prevention strategies.

Classically, colorectal cancers have primarily affected older generations. Its emergence among younger populations points to environmental factors that have taken effect within the space of a few decades. Examples of these are changes in diet, use of antibiotics, sedentary lifestyle, and obesity. Colorectal cancers carry varying mortality rates based on disease stage, sex, and geographical distribution. Due to the classical association with older age, younger people are less likely to be screened for the disease. This means that when the cancer is found in younger adults, it is often discovered at a more advanced and less treatable stage.

YO-CRC is an urgent healthcare issue that needs to be addressed quickly. Understanding colorectal cancer can help to provide peace of mind and may prompt younger adults to be screened for this disease. This article will explore the reasons behind rising CRC rates in young adults, the importance of early detection, and the implications for screening and prevention.

Risk Factors for Colorectal Cancer

Rising Incidence in Young Adults

While older adults are still more likely to be diagnosed with CRC, the incidence is rising rapidly in younger adults. Early reports of this increase were made in the USA, where researchers found a 17 percent increase in YO-CRC between 1973 and 1999. A later study observed an annual increase in incidence of 1.5 percent in men and 1.6 percent in women between the ages of 20 and 49 from 1992 to 2005. In this study, the largest increase in YO-CRC was observed in individuals aged between 20 and 29 years.

Global Variation in Incidence

Incidence rates of CRC differ between countries, however, in older adults (>50 years old), there is a general trend towards stabilization or decreases in incidence, while YO-CRC (20-49 years old) incidence is increasing relatively uniformly across populations since the 1990s. This variation in incidence between different regions and populations can be attributed to the availability and prescription of screening services, but could also be impacted by environmental factors like diet, as we’ll discuss later.

Genetic Factors

Individuals with a family history of CRC are at a higher risk for developing YO-CRC. 25 percent of individuals with YO-CRC have a first-degree relative with a history of CRC. Furthermore, YO-CRCs are more likely to have a mutation in a cancer susceptibility gene compared to older adults with CRC. Lynch syndrome is a hereditary condition that increases the risk of developing certain types of cancer, particularly colorectal cancer, due to inherited mutations in a subset of genes. These factors make screening even more important for high-risk individuals with a family history of CRC.

Impact of Environment and Lifestyle Choices

Cases of YO-CRC without a likely genetic route are called sporadic YO-CRC. Scientists point to many factors that may contribute to its onset.


Processed foods and red meat contain carcinogens that may contribute to YO-CRC. One study reports an increase in mutation rate in colon cells exposed to carcinogens found in cooked red meat. Furthermore, fast food consumption is associated with a higher risk of YO-CRC.

Obesity and Sedentary Lifestyles

In the US, sedentary jobs have increased by over 80 percent in the last seventy years. This has coincided with an increase in obesity and type-2 diabetes, which are both linked to YO-CRC. A recent study from Germany found that a higher BMI early in life increases the risk of YO-CRC.

Alcohol Consumption and Smoking

Alcohol consumption is thought to contribute to YO-CRC, but the mechanism is not clear. One hypothesis is that it alters the gut microbiome towards a more pro-oncogenic composition. A meta-analysis from 2023 found that current smokers had an increased risk of YO-CRC compared to people who never smoked.

Environmental Exposures

Exposure to environmental toxins such as industrial emissions and agricultural run-off may be related to the risk of YO-CRC. Evidence for this comes from geographic data within the US, where regions with higher exposure to these factors, such as Appalachia, have an increased incidence of YO-CRC.

Symptoms, Diagnosis, and Screening

Recognizing Early Symptoms

Like with other cancers, catching CRC early on can make a massive difference in terms of survival. Younger adults typically present with more advanced disease, which is likely due to a lack of screening availability for younger cohorts. This means it’s important to be informed about early symptoms which include:

  • Changes in bowel habits
  • Blood in stool
  • Abdominal pain
  • Unexplained weight loss
  • Fatigue

Diagnostic Approaches

There are several diagnostic tools available to detect colorectal cancer.


The most common diagnostic tool for CRC is colonoscopy with biopsy. This medical procedure involves a doctor using a camera to look inside your colon and taking small tissue samples to check for abnormalities. Flexible sigmoidoscopy offers a similar but less invasive approach, though it only examines the lower part of the bowel rather than the whole large intestine.

It’s important to note that young adults with CRC are more likely to be diagnosed after presenting symptoms than by an incidental finding with a scan. Non-invasive tests may provide a better option for early detection in the absence of symptoms.

Screening Guidelines and Recommendations

The increase in incidence, coupled with the higher likelihood of detecting an advanced tumor, puts the emphasis on early CRC screening for young adults.

American Cancer Society (ACS) Guidelines

The ACS recommends screening average-risk individuals beginning at age 45 and continuously screening until age 75. After this age, screening is optional based on patient preference and other factors. The frequency of screening depends on the method used. The age of eligibility for screening was dropped from 50 to 45 in 2018 to account for the increased incidence of CRC among younger adults.

US Preventive Services Task Force (USPSTF) Guidelines

Similar to the ACS, the USPSTF recommends screening for all adults aged 45 to 75, with the frequency of screening differing depending on the method used. Its most recent recommendations emphasized the need to address the rising incidence of CRC in young adults.

While both of these bodies have lowered the age of screening to 45, the fact remains that those over 50 have a far higher incidence rate. Thus, lowering the age further must balance resource allocation and the time taken to screen a significantly larger population, with the potential benefits of early screening.

Prevention and Treatment Strategies

Preventative Measures:

Preventative measures for YO-CRC primarily involve modifying behaviors and avoiding potential environmental exposures that increase the risk of the disease. Preventative measures may include the adoption of a healthier lifestyle including reducing or eliminating red meat, alcohol, smoking, and ultra-processed foods. Increasing physical activity early and being conscious of factors like BMI from childhood to adulthood could also help prevention.

Adopting a healthier lifestyle is a great decision, beyond reducing your risk of YO-CRC. However, it’s essential to take a practical approach to making changes. Begin integrating new habits and slowly remove old ones. Don’t hesitate to seek professional help from your doctor or mental health professional if you are dealing with addiction to substances like alcohol or cigarettes.

Advances in Treatment:

New therapies and surgical techniques are having a significant impact on patient outcomes. Particularly promising advances include:

Single-Incision Laparoscopic Surgery (SILS)

SILS for colorectal cancer is a minimally invasive technique using a single small incision, often in the belly button. This approach reduces pain, speeds up recovery, and leaves a smaller scar compared to traditional multiple-incision methods.

Targeted and Immunotherapies

Immune checkpoint inhibitors are gaining prominence in treating multiple cancers. Pembrolizumab is the first checkpoint inhibitor approved for the treatment of metastatic CRC. Targeted therapy Tucatinib targets a receptor called HER2, which promotes cancer growth. It received approval from the FDA for metastatic CRC in 2023.


Addressing the rise in YO-CRC requires urgent attention to screening and prevention. Early detection is crucial, as younger adults often present with more advanced disease stages. Regular screenings starting at age 45, as recommended by the ACS and USPSTF, can help catch the disease early. Lifestyle modifications, such as healthier diets, increased physical activity, and reduced alcohol and tobacco use, are important preventive measures. Awareness and education about YO-CRC symptoms and risk factors can empower younger adults to seek timely medical advice, ultimately improving outcomes and reducing the burden of this growing health concern.

Screening with a colonoscopy is also vital for early detection and cancer prevention. Take the Ezra five-minute quiz to learn more about your cancer risk and discover which tests might be beneficial for you. While a colonoscopy is the screening test for colon cancer, you can screen up to 13 other organs for potential cancers with the Ezra Full Body Scan. It could be the key to early detection.