Excess Weight Over Lifetime Hikes Risk for Colorectal Cancer

Marcia Frellick

March 18, 2022

Excess weight over a lifetime may play a greater role in a person's risk for colorectal cancer (CRC) than previously thought, according to new research.

In their paper published online March 17 in JAMA Oncology, the authors liken the cumulative effects of a lifetime with overweight or obesity to the increased risk of cancer the more people smoke over time.

This population-based, case-control study was led by Xiangwei Li, MSc, of the division of clinical epidemiology and aging research at the German Cancer Research Center in Heidelberg.

It looked at height and self-reported weight documented in 10-year increments starting at age 20 years up to the current age for 5,635 people with CRC compared with 4,515 people in a control group.

Odds for colorectal cancer increased substantially over the decades when people carried the excess weight long term compared with participants who remained within the normal weight range during the period.

Dr Hermann Brenner

Coauthor Hermann Brenner, MD, MPH, a colleague in Li's division at the German Cancer Research Center, said in an interview that a key message in the research is that "overweight and obesity are likely to increase the risk of colorectal cancer more strongly than suggested by previous studies that typically had considered body weight only at a single point of time."

The researchers used a measure of weighted number of years lived with overweight or obesity (WYOs) determined by multiplying excess body mass index by number of years the person carried the excess weight.

They found a link between WYOs and CRC risk, with adjusted odds ratios (ORs) increasing from 1.25 (95% confidence interval [CI], 1.09-1.44) to 2.54 (95% CI, 2.24-2.89) from the first to the fourth quartile of WYOs, compared with people who stayed within normal weight parameters.

The odds went up substantially the longer the time carrying the excess weight.

"Each SD increment in WYOs was associated with an increase of CRC risk by 55% (adjusted OR, 1.55; 95% CI, 1.46-1.64)," the authors wrote. "This OR was higher than the OR per SD increase of excess body mass index at any single point of time, which ranged from 1.04 (95% CI, 0.93-1.16) to 1.27 (95% CI 1.16-1.39)."

Brenner said that although this study focused on colorectal cancer, "the same is likely to apply for other cancers and other chronic diseases."

Prevention of overweight and obesity to reduce burden of cancer and other chronic diseases "should become a public health priority," he said.

Preventing Overweight in Childhood Is Important

Overweight and obesity increasingly are starting in childhood, he noted, and may be a lifelong burden.

Therefore, "efforts to prevent their development in childhood, adolescence, and young adulthood are particularly important," Brenner said.

The average age of the patients was 68 years in both the CRC and control groups. There were more men than women in both groups: 59.7% were men in the CRC group and 61.1% were men in the control group.

"Our proposed concept of WYOs is comparable to the concept of pack-years in that WYOs can be considered a weighted measure of years lived with the exposure, with weights reflecting the intensity of exposure," the authors wrote.

Study Helps Confirm What Is Becoming More Clear to Researchers

Kimmie Ng, MD, MPH, a professor at Harvard Medical School and oncologist at Dana-Farber Cancer Institute, both in Boston, said in an interview that the study helps confirm what is becoming more clear to researchers.

Dr Kimmie Ng

"We do think that exposures over the life course are the ones that will be most strongly contributing to a risk of colorectal cancer as an adult," she said. "With obesity, what we think is happening is that it's setting up this milieu of chronic inflammation and insulin resistance and we know those two factors can lead to higher rates of colorectal cancer development and increased tumor growth."

She said the ideal, but impractical, way to do the study would be to follow healthy people from childhood and document their weight over a lifetime. In this case-control study, people were asked to recall their weight at different time periods, which is a limitation and could lead to recall bias.

But the study is important, Ng said, and it adds convincing evidence that addressing the link between excess weight and CRC and chronic diseases should be a public health priority. "With the recent rise in young-onset colorectal cancer since the 1990s there has been a lot of interest in looking at whether obesity is a major contributor to that rising trend," Ng noted. "If obesity is truly linked to colorectal cancer, these rising rates of obesity are very worrisome for potentially leading to more colorectal cancers in young adulthood and beyond."

The study authors and Ng report no relevant financial relationships.

The new research was funded by the German Research Council, the Interdisciplinary Research Program of the National Center for Tumor Diseases, Germany, and the German Federal Ministry of Education and Research.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


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