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Bowel cancer in younger women linked to obesity

Obesity was associated with an increased risk of early-onset colorectal cancer (CRC) among younger women, according to a large, 14-year study by Washington University researchers.

. The study, which used data from a large group of US nurses, mainly included white women so the findings need to be confirmed in other ethnicities and among men. Cancer Research UK’s Katie Patrick said the results served as a reminder that keeping a healthy weight is important at any age.

The study, by researchers at Washington University School of Medicine in St Louis, Missouri, followed 85,256 women over an average of 14 years, using body mass index (BMI) as an indicator of obesity.

BMI works out if you have a healthy weight for your height. People with a BMI of 25 or over are classified as overweight, and those with a BMI of 30 or over are classified as obese.

There were 114 cases of early onset bowel cancer among the women in the study, and obesity – as judged by a BMI over 30 – was linked to a higher risk of developing the disease. A higher BMI at the age of 18 and weight gain of more than 40 kg since early adulthood were also both linked to an increased risk of early onset bowel cancer.

Patrick said that while bowel cancer cases remain uncommon among younger people, more still needs to be done to help reduce bowel cancer risk at any age. She said: “Bowel cancer in younger people is still rare, with around 630 women aged 25-44 diagnosed in the UK each year.

“As well as keeping a healthy weight, there are lots of other ways to reduce bowel cancer risk, such as not smoking, eating plenty of foods high in fibre and cutting down on alcohol and processed and red meat.

“Keeping a healthy weight helps to reduce cancer risk for adults at any age, which is why it’s vital that the Government acts to help make healthy choices easier for everyone.”

Importance: Colorectal cancer (CRC) incidence and mortality among individuals younger than 50 years (early-onset CRC) are increasing. The reasons for such increases are largely unknown, although the increasing prevalence of obesity may be partially responsible.
Objective: To investigate prospectively the association between obesity and weight gain since early adulthood with the risk of early-onset CRC.
Design, Setting, and Participants: The Nurses’ Health Study II is a prospective, ongoing cohort study of US female nurses aged 25 to 42 years at study enrollment (1989). A total of 85 256 women free of cancer and inflammatory bowel disease at enrollment were included in this analysis, with follow-up through December 31, 2011. Validated anthropomorphic measures and lifestyle information were self-reported biennially. Statistical analysis was performed from June 12, 2017, to June 28, 2018.
Exposures: Current body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared), BMI at 18 years of age, and weight gain since 18 years of age.
Main Outcomes and Measures: Relative risk (RR) for incident early-onset CRC.
Results: Among the 85 256 women studied, 114 cases of early-onset CRC were documented (median age at diagnosis, 45 years; interquartile range, 41-47 years) during 1 196 452 person-years of follow-up. Compared with women with a BMI of 18.5 to 22.9, the multivariable RR was 1.37 (95% CI, 0.81-2.30) for overweight women (BMI, 25.0-29.9) and 1.93 (95% CI, 1.15-3.25) for obese women (BMI, ≥30.0). The RR for each 5-unit increment in BMI was 1.20 (95% CI, 1.05-1.38; P = .01 for trend). 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 of age and weight gain since 18 years of age contributed to this observation. Compared with women with a BMI of 18.5 to 20.9 at 18 years of age, the RR of early-onset CRC was 1.32 (95% CI, 0.80-2.16) for women with a BMI of 21.0 to 22.9 and 1.63 (95% CI, 1.01-2.61) for women with a BMI of 23.0 or greater at 18 years of age (P = .66 for trend). Compared with women who had gained less than 5.0 kg or had 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 = .007 for trend).
Conclusions and Relevance: Obesity was associated with an increased risk of early-onset CRC among women. Further investigations among men and to elucidate the underlying biological mechanisms are warranted.

Po-Hong Liu; Kana Wu; Kimmie Ng; Ann G Zauber; Long H Nguyen; Mingyang Song; Xiaosheng He; Charles S Fuchs, ; Shuji Ogino; Walter C Willett; Andrew T Chan; Edward L Giovannucci; Yin Cao

[link url="https://www.cancerresearchuk.org/about-us/cancer-news/news-report/2018-10-15-bowel-cancer-in-younger-women-linked-to-obesity"]Cancer Research UK material[/link]
[link url="https://jamanetwork.com/journals/jamaoncology/article-abstract/2705608"]JAMA Oncology abstract[/link]

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