Lifetime excess weight linked to colorectal cancer risk
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Excess weight had a stronger impact on colorectal cancer risk than suggested in previous studies that did not consider cumulative lifetime exposure, according to a study published in JAMA Oncology.
“Excess weight has long been recognized as a risk factor for colorectal cancer (and several other cancers), but risk estimates from essentially all previous studies were based on excess weight determined at one single point of time. We wanted to derive more accurate risk estimates by considering lifetime excess weight,” Hermann Brenner, MD, MPH, professor of epidemiology at Heidelberg University and head of the division of clinical epidemiology and aging research at German Cancer Research Center in Heidelberg, Germany, told Healio.
Methodology
The analysis included 10,150 individuals — 5,635 with colorectal cancer (mean age, 68.4 years; standard deviation [SD], 10.9; 59.7% men) and 4,515 controls (mean age, 68.5 years; SD, 10.6; 61.1% men) — from an ongoing population-based control study that began in Germany in 2003.
Brenner and colleagues collected height and self-reported weight (documented in 10-year increments, starting at age 20 years) from participants. They used linear interpolation to calculate BMI for each year of age from 20 years to the current age. They calculated excess BMI as the difference of the person’s reported BMI from 25 kg/m2 for each year to age at diagnosis or recruitment. Next, they summed the excess BMI across ages to derive a measure of cumulative lifetime excess weight. Researchers recorded this figure as weighted number of years lived with overweight or obesity (WYOs), determined as year multiplied by excess BMI, because it “sums the years lived with excess weight, with the contribution of each single year of age with excess weight being weighted by excess BMI at that age,” they wrote.
Key findings
Results showed an association between WYOs and colorectal cancer risk; adjusted ORs increased from 1.25 (95% 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 participants who stayed within the normal weight range, researchers reported.
Additionally, each standard deviation increment in WYOs exhibited an association with a 55% increase of colorectal cancer risk (adjusted OR = 1.55; 95% CI, 1.46-1.64) — with an OR higher than ORs per standard deviation increase of excess BMI 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).
Implications
Measures to halt and reverse the increase in prevalence of overweight and obesity could prevent many cases of colorectal cancer and possibly other obesity-related cancers, Brenner and colleagues wrote.
“The lifetime approach should also be used to study the effect of excess weight for other cancers and health outcomes, in order to obtain more accurate risk estimates and to derive a more solid basis for the design of effective prevention strategies,” Brenner said.
In an accompanying editorial, Patrick T. Bradshaw, PhD, associate professor of epidemiology and endowed chair of Martin Sisters Medical Research & Public Health at University of California, Berkeley School of Public Health, wrote that the research “shines a light on the utility of metrics that characterize long-term exposures in this area.”
“There is significant insight to be gained in the use of methods to characterize longitudinal exposures in epidemiological analyses, and researchers should continue to design studies and data collection strategies to take advantage of them,” Bradshaw wrote. “With several approaches available, researchers should understand the potential interpretations that could be taken from each and which may be most illuminating.”
References:
Bradshaw PT. JAMA Oncol. 2022;doi:10.1001/jamaoncol.2022.0061.
Li X, et al. JAMA Oncol. 2022;doi:10.1001/jamaoncol.2022.0064.
For more information:
Hermann Brenner, MD, MPH, can be reached at Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, INF 581, Heidelberg 69120, Germany; email: h.brenner@dkfz-heidelberg.de.
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