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).”
Dr. 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,” Dr. 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.