To the Editor In their recent study, Iyengar and colleagues1 investigated the association between various measures of body fat and breast cancer incidence, focusing on postmenopausal women within the normal range for body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared). Previous epidemiological studies have described a nonintuitive association between BMI and rates of breast cancer; higher BMI appears to be associated with lower breast cancer incidence in premenopausal women but a higher incidence in postmenopausal women.2 In the present study,1 the authors investigated a set of metrics to better understand the relationship between body fat and breast cancer risk and to understand possible causal factors for this cancer type. Part of the rationale for using these absolute measures of body fat is that individuals of a given BMI can have vastly different levels of total body fat and lean body mass. As described by Iyengar and colleagues,1 increasing levels of fat are correlated with numerous markers of inflammation. Different amounts of body fat could have predictive power for determining the risk of breast cancer and may even play a direct causal role.
Lee KJ. Accounting for Height in an Analysis of Body Fat and Breast Cancer Risk. JAMA Oncol. Published online May 30, 20195(7):1067–1068. doi:10.1001/jamaoncol.2019.1091
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