Overweight, obese adolescents at greater risk for colorectal cancer

Being overweight or obese in adolescence appeared linked to a greater risk for subsequent colon cancers in men and women, according to study results published in Cancer.

Obesity, but not overweight, in adolescence also increased the risk for subsequent rectal cancer.

“This is a huge cohort with a minimum follow-up of 10 years, and all individuals had measured BMI, not just reported or recalled,” Zohar Levi, MD, of the Rabin Medical Center and Tel Aviv University in Israel, said in a press release. “This is the largest study ever, including both men and women, and it had the power to prove the importance of BMI at age 17 on events later in life.”

The potential impact of adolescent overweight and obesity on chronic disease later in life has been a growing concern. Although adult obesity has been linked to an increased risk for colorectal cancer in men and women, data on adolescent obesity and risk for colorectal cancer have been conflicting.

Levi and colleagues evaluated data from 1.08 million Jewish men and 707,212 Jewish women who underwent health examinations when aged 16 to 19 years (mean age at baseline examination, 17.4 years) between 1967 and 2002. According to CDC classification, 7.8% of the population was overweight and 3% were obese.

Researchers followed these individuals and linked them to the national cancer registry through 2012.

Median follow-up was 23.3 years.

During that time, 2,967 incidence cases of colorectal cancer occurred, including 1,977 among men — or 1,403 colon cancers and 574 rectum cancers — and 990 among women, 764 of which were in the colon and 226 in the rectum.

Median age was 40.6 years at the end of follow-up and 49.4 years at colorectal cancer diagnosis.

Researchers observed a greater risk for colon cancer in men who were overweight (HR = 1.53; 95% CI, 1.28-1.84) and obese (HR = 1.54; 95% CI, 1.15-2.06) and women who were overweight (HR = 1.54; 95% CI, 1.22-1.93) and obese (HR = 1.51; 95% CI, 0.89-2.57).

The trend became significant after a BMI of 23.4 kg/m² in men and 23.6 kg/m² in women.

A greater risk for rectal cancer only occurred for obese men (HR = 1.71; 95% CI, 1.11-2.65) and women (HR = 2.03; 95% CI, 0.9-4.58). The trend became significant after a BMI of 29.6 kg/m² in men and 30.6 kg/m² in women.

Limitations of the analysis included the young age of the cohort and a lack of data on diet, physical activity, smoking and family history.

“Several explanations have been suggested for the association of a higher BMI with colorectal cancer,” the researchers wrote. “These include downregulation of adiponectin; upregulation of leptin, interleukin-6 and tumor necrosis factor alpha; increased insulin and insulin-like growth factor 1; the impact of nonalcoholic steatohepatitis; low-grade inflammation; and an altered immune response.” – by Alexandra Todak

Disclosure: The researchers report no relevant financial disclosures.