Originally published by 2 Minute Medicine^® (view original article). Reused on AccessMedicine with permission.

1. In a case-control study based in Sweden, females born by C-section had greater odds of developing early-onset colorectal cancer (CRC), compared to females born by vaginal delivery.

2. No association was found between males born by C-section and early-onset CRC.

Evidence Rating Level: 3 (Average)

In the USA and Europe, there have been reports of increasing incidence of colorectal cancer (CRC) in patients less than 50 years old. Risk factors such as obesity, diabetes, and metabolic syndrome, have been identified for early-onset CRC. As well, the gut microbiome has been linked to the development of CRC. Altogether, experts have wondered if there may be an early-life etiology for metabolic dysfunction that leads to CRC. Furthermore, reports from the USA have showed that the incidence of early-onset CRC increased with each successive birth cohorts. One hypothesis is that this may be linked to increasing rates of C-section deliveries, which have been associated with obesity and diabetes, likely due to gut dysbiosis early in life. Therefore, this case-control study based in Sweden examined individuals with early-onset CRC, stratifying by their mode of birth, either vaginal delivery or C-section. The study population included patients from 1991 to 2007 between ages 18 and 49, who were diagnosed with histopathologic findings of CRC. In total, there were 705 individuals included with early-onset CRC, matched by age, sex, birth year, and country to 3509 controls. The study found that those born by C-section did not have higher odds of early-onset CRC (adjusted odds ratio 1.28, 95% CI 0.91-1.79). However, when stratifying by gender, there was an association between females delivered C-section and early-onset CRC (aOR 1.62, 95% CI 1.01-2.60), but not males (aOR 1.05, 95% CI 0.64-1.72). Overall, this study found that females born by C-section had increased odds of developing early-onset CRC, compared to females born by vaginal delivery.

Click to read the study in JAMA Network Open

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