Excess weight over time associated with increased CRC risk
A German study found that the weighted number of years lived with overweight and obesity was associated with a higher risk for colorectal cancer (CRC) than excess body mass index at a single point in time.
Patients with cumulative lifetime exposure to excess weight may be at higher risk for colorectal cancer (CRC), according to a recent study.
Researchers in Germany performed a population-based case-control study that collected data on patients' height and self-reported weight at 10-year intervals beginning at age 20 years. Excess body mass index (BMI) was calculated for each year from age 20 years to current age and added across ages to calculate the weighted number of years lived with overweight or obesity (WYOs). Patients who had a BMI below 25 kg/m2 were considered to have an excess BMI of 0. The researchers compared the relative risk of CRC according to lifetime exposure to excess weight with relative risks according to BMI at various ages. Results were published March 17 by JAMA Oncology.
The study included 5,635 patients with CRC and 4,515 controls. The mean age was 68.4 years and 68.5 years, respectively, and 59.7% and 61.1%, respectively, were men. WYOs were associated with CRC risk, with adjusted odds ratios (ORs) increasing from 1.25 (95% CI, 1.09 to 1.44) in the first WYO quartile to 2.54 (95% CI, 2.24 to 2.89) in the fourth WYO quartile versus patients who remained at normal weight. Each standard deviation increment in WYOs was associated with a 55% increase in CRC risk (adjusted OR, 1.55; 95% CI, 1.46 to 1.64), compared with a range of 1.04 (95% CI, 0.93 to 1.16) to 1.27 (95% CI, 1.16 to 1.39) for excess BMI at any single point in time.
The researchers noted that selection bias was possible, that weight was based on self-report, and that the study used only one measure of overweight and obesity. “The findings of this large-scale population-based case-control study suggest that excess weight may have substantially higher ORs associated with CRC risk than previously disclosed by epidemiologic studies that had mostly considered weight at a single point of time,” they concluded. “Use of the concept of WYOs in further studies, including prospective cohort studies, may help to more fully disclose the association of excess weight not only with CRC but also with other cancers and diseases.”
The authors of an accompanying editorial said the study is an important contribution to the literature on obesity and cancer risk because it “shines a light on the utility of metrics that characterize long-term exposures in this area.” They called for additional studies designed to examine longitudinal exposures. “With several approaches available, researchers should understand the potential interpretations that could be taken from each and which may be most illuminating,” the editorialists wrote. “Methods that facilitate interpretation of heterogeneous patterns of exposure on disease risk may be especially useful for understanding the association between long-term exposures and cancer risk.”