What is causing the increasing incidence of colon cancer among young people?

Rising Incidence of Colorectal Cancer Among Young People: Causes and Concerns

The increasing incidence of colorectal cancer (CRC) among young people is primarily attributed to lifestyle and environmental factors associated with Western diets, physical inactivity, obesity, and other modifiable risk factors, though the exact causes remain under investigation. 1

Epidemiological Trends

The epidemiological data clearly shows concerning trends:

• CRC incidence has been steadily increasing in younger Americans for several decades, with the sharpest rise seen in rectal cancer 1
• For individuals aged 20-29,30-39, and 40-49, there has been a 5.6%, 1.6%, and 0.9% annual percentage increase in overall colorectal adenocarcinomas, respectively 1
• Rectal cancer incidence rates increased 3.2% per year from 1974 to 2013 in adults aged 20-29 years 1
• The proportion of CRC cases in adults younger than 55 years increased from 11.6% during 1989-1990 to 16.6% during 2012-2013 for colon tumors and from 14.6% to 29.2% for rectal tumors 1
• By 2030, researchers estimate that colon and rectal cancer incidence rates will increase by 90.0% and 124.2%, respectively, for patients 20-34 years of age 1

Primary Contributing Factors

1. Lifestyle and Dietary Factors

Several modifiable risk factors have been strongly associated with the increasing incidence:

• Western Diet: High consumption of red and processed meats, refined carbohydrates, and low intake of fruits, vegetables, and fiber 1, 2
• Physical Inactivity: May be responsible for 13-14% of colon cancer cases, an attributable risk greater than family history 3
• Obesity and Excess Body Weight: Central adiposity is a consistent risk factor 2
• Alcohol Consumption: High alcohol intake, particularly when combined with low folate intake 2
• Smoking: Particularly early in life 2

A study of US women found that approximately 37% of colon cancer cases could be prevented through adherence to healthy lifestyle behaviors, including maintaining normal BMI, regular physical activity, moderate alcohol consumption, limited smoking, multivitamin use, and adequate calcium intake 4.

2. Metabolic Factors

• Chronic Hyperinsulinemia: Insulin resistance and subsequent hyperinsulinemia induced by excess energy intake and aspects of the Western diet (saturated fats and refined carbohydrates) may increase risk of colon cancer 2
• Insulin-like Growth Factor-1 (IGF-1): May play a role, though our understanding of modifiable factors that influence IGF-1 levels remains limited 2

3. Birth Cohort Effect

• Risk of CRC decreased for birth cohorts from 1890 to 1950 but has increased for every generation born since 1950 1
• For someone born in 1990, the age-specific risk of colon cancer is double that of someone born in 1950, and for rectal cancer, the risk has quadrupled 1
• This suggests that the greater burden of CRC in the population younger than 50 years is not just a transient phenomenon but reflects a generational shift in risk 1

Clinical Implications and Concerns

Several concerning trends have been identified:

• Delayed Diagnosis: Young patients often experience significant delays in diagnosis after symptom onset (60 days vs. 30 days for older patients) 1
• Advanced Stage at Diagnosis: Young individuals are more likely to be diagnosed with distant versus localized stage CRC 1
• Left-Sided Tumor Shift: There is an increasing proportion of rectal cancers among young adults 5
• Racial Disparities: Young-onset CRC occurs disproportionately in Black and other minority groups, though recent data suggests increasing mortality rates among young white individuals as well 1

Prevention Strategies

Given that approximately half of all CRC cases are attributable to modifiable risk factors 1, prevention strategies should focus on:

• Promoting physical activity and maintaining healthy weight
• Encouraging diets rich in fruits, vegetables, and fiber while limiting red and processed meats
• Reducing alcohol consumption and smoking cessation
• Considering earlier screening for those with risk factors
• Prompt evaluation of concerning symptoms in young adults, particularly rectal bleeding

Conclusion

The rising incidence of CRC among young people represents a significant public health concern. While the exact causes remain under investigation, the evidence strongly suggests that lifestyle factors associated with Western diets and sedentary behaviors play a major role. Healthcare providers should maintain a high index of suspicion for CRC in young patients with concerning symptoms, and public health efforts should focus on promoting lifestyle modifications that may reduce risk.