Those with a BMI greater than 30 have twice the risk of early-onset colorectal cancer.
Compared with women with normal body mass index (BMI), overweight or obese women with BMIs greater than 30, had almost twice the risk of developing colorectal cancer before age 50, say researchers at Washington University School of Medicine in St Louis.
The study included data from 85,256 women aged 25 to 44 in the Nurses’ Health Study II, which began in 1989. The researchers collected detailed information on body weight throughout the life course, family and endoscopy histories, and lifestyle factors. Up to 2011, doctors diagnosed 114 colorectal cancer cases under the age of 50.
Never too early to work towards a healthy weight
“Our findings really highlight the importance of maintaining a healthy weight, beginning in early adulthood for the prevention of early-onset colorectal cancer,” said co-senior author and cancer epidemiologist Yin Cao, an assistant professor of surgery in the Division of Public Health Sciences at Washington University.
“We hypothesised that the obesity epidemic may partially contribute to this national and global concern in early-onset colorectal cancer rates. But we were surprised by the strength of the link and the contribution of obesity and weight change since early adulthood.”
The researchers emphasised that this is an association study, which does not establish that increasing weight is a cause of early-onset colorectal cancer.
More studies are needed to uncover the best ways to identify young people at high risk of colorectal cancer at younger ages.
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Cancer now found in younger folks
In the United States, overall rates of new colorectal cancer cases and deaths from the disease have decreased steadily since 1980, largely owing to recommended colonoscopy screening starting at age 50. But for reasons that remain unknown, new cases of, and deaths due to, both colon and rectal cancers have been increasing for younger adults aged 20 to 49.
The American Cancer Society recently lowered the recommended age at which most people should undergo a first screening colonoscopy.
The new guidelines recommend screening beginning at age 45, down from the previous recommendation of age 50.
A version of this article appeared in the print edition of The Straits Times on October 16, 2018, with the headline ‘Obesity linked to increased risk of colorectal cancer in women’.
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