MONDAY, Nov. 26, 2018 (HealthDay News) — Obesity is associated with an increased risk for early-onset colorectal cancer (CRC) among women, according to a study recently published in JAMA Oncology.

Po-Hong Liu, M.D., M.P.H., from Massachusetts General Hospital in Boston, and colleagues used data from women aged 25 to 42 years at enrollment in 1989 in the Nurses’ Health Study II to identify 85,256 women free of cancer and inflammatory bowel disease at enrollment. Follow-up lasted through Dec. 31, 2011.

The researchers found 114 cases of early-onset CRC during the study period (median age at diagnosis, 45 years). For overweight women (body mass index [BMI], 25 to 29.9 kg/m²), the multivariable relative risk (RR) was 1.37 (95 percent confidence interval [CI], 0.81 to 2.3), and for obese women (BMI, ≥30 kg/m²), it was 1.93 (95 percent CI, 1.15 to 3.25 kg/m²), compared with women with a BMI of 18.5 to 22.9 kg/m². For each five-unit increment in BMI, the RR was 1.2 (P = 0.01 for trend). This finding was attributable to both BMI at age 18 years and weight gain since age 18 years. The RR of early-onset CRC was 1.32 (95 percent CI, 0.8 to 2.16) for women with a BMI of 21 to 22.9 kg/m² and 1.63 (95 percent CI, 1.01 to 2.61) for women with a BMI of ≥23 kg/m² at 18 years of age versus women with a BMI of 18.5 to 20.9 kg/m² at 18 years of age (P = 0.66 for trend). Similarly, the RR of early-onset CRC was 1.65 (95 percent CI, 0.96 to 2.81) for women gaining 20 to 39.9 kg and 2.15 (95 percent CI, 1.01 to 4.55) for women gaining ≥40 kg (P = 0.007 for trend) versus women who had gained <5 kg or had lost weight.

“Further investigations among men and to elucidate the underlying biological mechanisms are warranted,” the authors write.

One author disclosed financial ties to the pharmaceutical industry.

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