Obesity and Colorectal Cancer Risk in Women

Obesity is associated with an increased risk of early-onset colorectal cancer (CRC) in women, according to a study published in JAMA Oncology 

The researchers used data from the prospective, ongoing cohort Nurses’ Health Study II, which follows U.S. female nurses aged 25 to 42 years at enrollment in 1989. A total of 85,256 women without cancer and inflammatory bowel disease at enrollment were included and followed through December 31, 2011.  

During 1,196,452 person-years of follow-up, there were 114 cases of early-onset CRC at a median age at diagnosis of 45 years (range = 41-47 years). Women with a body mass index (BMI) of ≥30 kg/m2 had an increased risk of CRC (relative risk [RR] = 1.93; 95% CI, 1.15-3.25) compared with overweight women (BMI=25.0-29.9 kg/m2; RR=1.37; 95% CI, 0.81-2.30) and women with a normal BMI (18.5-20.9 kg/m2; RR=1.32; 95% CI, 0.80-2.16).  

Similar associations were observed among women without a family history of CRC and without lower endoscopy within the past 10 years. Both BMI at 18 years and weight gain since 18 then contributed to this increased risk.  

Each five-unit increment increase in BMI was associated with a RR of 1.2 (95% CI, 1.05-1.38; P=0.01). Compared with women who had gained <5.0 kg or lost weight, the RR of early-onset CRC was 1.65 (95% CI, 0.96-2.81) for women gaining 20.0 to 39.9 kg and 2.15 (95% CI, 1.01-4.55) for women gaining 40.0 kg or more (P=0.007). 

Colorectal cancer is on the rise in younger patients.  

Obesity is now linked to 12 cancer types. 

SourceJAMA Oncology