New study links obesity to colorectal cancer



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Washington: According to a recent study, overweight or obese women are up to twice as likely to develop colorectal cancer before the age of 50, unlike women whose mass index body is considered normal.

In the United States, overall rates of new cases of colorectal cancer and deaths from the disease have steadily declined since 1980, largely as a result of screening recommended for colonoscopy from the age of 50 years. For reasons that remain unknown, new cases and deaths due The cancers of the colon and rectum have increased in young adults aged 20 to 49 years.

The study is one of the first epidemiological analyzes of potential factors for early and diagnosed colorectal cancer in children under 50 years of age. The researchers found that a higher current BMI, an 18-year-old BMI, and weight gain since early adulthood were associated with colorectal cancer risk in those under 50 years of age.

The study included data on 85,256 women aged 25 to 44 in the nurses' health study II begun in 1989. Researchers collected detailed information on body weight throughout the study. from life, family history and endoscopy and factors two to four years. Until 2011, doctors had diagnosed 114 cases of colorectal cancer under the age of 50 years.

"Our results really highlight the importance of maintaining a healthy weight, early in adulthood, for the prevention of colorectal cancer at an early stage," said Yin Cao, co-author and cancer epidemiologist.

"We hypothesized that the obesity epidemic might contribute in part to this national and global concern with regard to early-onset colorectal cancer rates, but we have been surprised by the strength of the bond and by the contribution of obesity and weight change since the beginning of adulthood, "added Cao.

Compared to women with the lowest BMI (18.5 to 22.9 kg per square meter), women with the highest BMI (greater than 30) are at almost twice the risk higher colorectal cancer at an early stage. According to the Centers for Disease Control and Prevention, the normal BMI range is between 18.5 and 24.9 kg per square meter. BMIs between 25 and 29.9 are considered overweight, and BMIs greater than 30 are considered obese.

Early-onset colorectal cancer remains relatively rare (about eight cases per 100,000 people), but as these populations are not screened systematically, cases are often diagnosed at one time. later stage of the disease, making them much more difficult to treat.

The researchers estimated that about 22% of early-stage colorectal cancers could have been prevented if all participants had a normal BMI between 18.5 and 24.9. At the population level, this represents thousands of potentially preventable cases of colorectal cancer among the younger population.

The researchers also found that the higher risk of colorectal cancer at early onset was associated with increased BMI, even in women with no family history of the disease.

"There are few known risk factors for colorectal cancer at an early stage," said Edward Giovannucci, MD, ScD, of Harvard T.H. Chan School of Public Health. "If the age of screening is pushed back before the age of 50, BMI may be one of the factors to be considered. Yet the cost analysis and the risk-benefit analysis for early detection still need to be performed. "

The researchers pointed out that it was an association study – it does not establish that weight gain is a cause of colorectal cancer at one stage early. BMI may serve as a substitute for other risk factors that may affect the risk of colorectal cancer, including the metabolic syndrome and diabetes, which have also increased at the population level.

The researchers said that further studies would be needed to discover the best ways to identify young people at high risk of colorectal cancer at an earlier age. And since this study was restricted to predominantly white women, further research is needed to determine whether these associations are valid for men and for various racial and ethnic populations.

The study was published in the Journal JAMA Oncology.

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