Central obesity metrics more accurate than BMI in estimating excess weight-related CRC
Key takeaways:
- The proportion of CRC cases attributable to high BMI were “substantially lower” than those attributable to central obesity measures.
- Results demonstrate the importance of overcoming obesity to prevent CRC.
Central obesity measures of waist circumference and waist-to-hip ratio appear to be more accurate and consistent indicators of colorectal cancer incidence compared with BMI, according to a study published in JAMA Network Open.
“The proportion of CRC cases attributable to excess weight, commonly known as population attributable fraction (PAF), has been estimated to be approximately 5.8% in men and 7% in women worldwide in 2012,” Fatemah Safizadeh, MSc, of the division of clinical epidemiology and aging research at the German Cancer Research Center, and colleagues wrote. “However, PAFs attributable to excess BMI are likely underestimated due to the underestimation of the risk estimates for the association between high BMI and CRC incidence, which are used in PAF calculation.”
They continued, “Central obesity measures have shown stronger associations with CRC incidence compared with BMI in several studies.”
Using population-based data from 458,543 individuals (median age, 57 years; 53.3% women) from the UK Biobank, Safizadeh and colleagues compared the proportion of CRC cases attributable to central obesity measures of high waist circumference and waist-to-hip ratio vs. those attributable to BMI. At baseline, the cohort’s median BMI, waist circumference and waist-to-hip ratio were 26.7 kg/m2, 90 cm and 0.87, respectively.
Results showed 5,944 individuals developed CRC during a median follow-up of 11.8 years. When comparing the highest vs. lowest quartiles, waist circumference (HR = 1.37; 95% CI, 1.27-1.49) and waist-to-hip ratio (HR = 1.4; 95% CI, 1.29-1.51) had stronger associations with CRC incidence vs. BMI (HR = 1.23; 95% CI, 1.14-1.33). These associations “became comparable” after excluding the first 7 years of follow-up (1.4 vs. 1.43 vs. 1.37).
Additionally, results showed the proportion of CRC cases attributable to high BMI were “substantially lower” (9.9%; 95% CI, 5.5-14.4) compared with high waist circumference and waist-to-hip ratio (17.3%; 95% CI, 12.3-22.1 and 17.6%; 95% CI, 12.9-22.2). These proportions similarly became comparable following the exclusion of the first 7 years of follow-up (BMI: 15.7%; 95% CI, 8.9-22.4; waist circumference: 16.9%; 95% CI, 9.8-23.8; waist-to-hip ratio: 18%; 95% CI, 11.5-24.6).
“We demonstrated that calculating the proportion of CRC cases attributable to central obesity, as opposed to the routine approach of using BMI, provided more accurate estimates of the PAFs of obesity-related CRC cases,” Safizadeh and colleagues wrote. “We recommend incorporating central obesity measures, such as waist circumference and waist-to-hip ratio, alongside BMI, which does not account for fat mass distribution, in estimating the burden of CRC due to excess weight and the potential for prevention.”
They continued, “Our PAF findings underline the importance of efforts to limit and overcome the obesity epidemic in CRC prevention.”
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