Am J Epidemiol：用体质指数判定癌症风险或需重新思考

近日，刊登在国际杂志American Journal of Epidemiology上的一项研究报告中，来自叶史瓦大学的研究者报告说，常见的用来衡量是否肥胖的体质指数（BMI）并不是估计疾病发病风险的最好判断依据，尤其是判断特定癌症的发病风险。

BMI是通过将个人的体重和身高分开进行计算的，或者是W/H2，而且BMI已经被广泛在大型的研究中用于分析个体的体重质量指数。BMI介于18.5和24.9之间被认为是最为理想的，超过30就被认为是肥胖了。

研究者当前的研究是想确定，相比BMI，是否改变体重和身高的措施会影响特定癌症的发病风险。对将近90，000个加拿大妇女的体重和身高数据进行分析，研究者通过改变BMI公式，改变了W/Hx中的x变量，观察是否这种改变可以更好地对19种不同癌症的发病风险进行更好的预测。

W/Hx公式中所有x的变量值都和特定癌症风险相关，其为0.8的时候可预测子宫内膜癌，1.3时可预测吸烟者是否患肺癌，1.7的时候可预测绝经后乳腺癌。

研究者表示，这些研究发现都需要在其它研究中进行证实，W/Hx公式的最优值应该依据研究人群、疾病而异，而BMI或许并不是最优化的判定疾病的标准。

编译自：Rethinking Body Mass Index (BMI) for Assessing Cancer Risk

doi:10.1093/aje/kws270
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Scaling of Weight for Height in Relation to Risk of Cancer at Different Sites in a Cohort of Canadian Women

Geoffrey C. Kabat*, Moonseong Heo, Anthony B. Miller and Thomas E. Rohan

Many studies have examined the associations of body mass index (weight (kg)/height (m)2) with risk of various cancers. However, optimal scaling of weight for height may depend on the population studied. The authors used data from a large cohort study of women (Canadian National Breast Cancer Screening Study, 1980–2000; n = 89,835) to examine how the scaling of weight for height (W/Hx) influenced the association with risk of 19 different cancers. Cox proportional hazards models were used to estimate the hazard ratio for each cancer site with W/Hx, with x increasing from 0 to 3.0 by increments of 0.1. The correlation between weight and W/Hx decreased monotonically with increasing x, whereas W/Hx was minimally correlated with height when x = 1.4. W/Hx showed significant positive associations with postmenopausal breast cancer, endometrial cancer, kidney cancer, and lung cancer in never smokers. W/Hx was inversely associated with lung cancer in ever smokers. The value of x for which W/Hx produced the largest statistically significant hazard ratio ranged from 0.8 (endometrial cancer) to 1.7 (postmenopausal breast cancer). For lung cancer in ever smokers, the inverse association was statistically significant for all values of x. These findings suggest that the scaling of weight for height may vary depending on the cancer site and that optimal scaling may be considerably different from W/H2 or, alternatively, that a range of scaling should be considered when examining the association of body weight with risk of disease.