Family history and body mass index (BMI) are well‐known risk factors for colorectal cancer (CRC), however, their joint effects are not well described. Using linked data for genealogy, self‐reported height and weight from driver's licenses, and the Utah Surveillance, Epidemiology, and End‐Results cancer registry, we found that an increasing number of first‐degree relatives (FDR) with CRC is associated with higher standardized incidence ratio (SIR) for overweight/obese probands but not for under/normal weight probands. For probands with two CRC‐affected FDRs, the SIR = 1.91 (95% CI [0.52, 4.89]) for under/normal weight probands and SIR = 4.31 (95% CI [2.46, 7.00]) for overweight/obese probands. In the absence of CRC‐affected FDRs, any number of CRC‐affected SDRs did not significantly increase CRC risk for under/normal weight probands, but for overweight/obese probands with at least three CRC‐affected SDRs the SIR = 2.68 (95% CI [1.29, 4.93]). In the absence of CRC‐affected FDRs and SDRs, any number of CRC‐affected third‐degree relatives (TDRs) did not increase risk in under/normal weight probands, but significantly elevated risk for overweight/obese probands with at least two CRC‐affected TDRs was observed; SIR = 1.32 (95% CI [1.04, 1.65]). For nonsyndromic CRC, maximum midlife BMI affects risk based on family history and should be taken into account for CRC risk communication when possible.

中文翻译：

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基于扩展家族史和体重指数的结直肠癌风险。

家族史和体重指数 (BMI) 是众所周知的结直肠癌 (CRC) 危险因素，然而，它们的联合效应并未得到很好的描述。使用关联的谱系数据、驾驶执照上的自我报告身高和体重以及犹他州监测、流行病学和最终结果癌症登记处，我们发现越来越多的一级亲属 (FDR) 患有 CRC超重/肥胖先证者的标准化发病率 (SIR)，但不是体重不足/正常体重的先证者。对于具有两个受 CRC 影响的 FDR 的先证者，体重不足/正常的先证者的 SIR = 1.91（95% CI [0.52, 4.89]），超重/肥胖的先证者的 SIR = 4.31（95% CI [2.46, 7.00]）。在没有受 CRC 影响的 FDR 的情况下，任何数量的受 CRC 影响的 SDR 都不会显着增加体重不足/正常先证者的 CRC 风险，但对于至少有 3 个受 CRC 影响的 SDR 的超重/肥胖先证者，SIR = 2.68（95% CI [1.29, 4.93]）。在没有受 CRC 影响的 FDR 和 SDR 的情况下，任何数量的受 CRC 影响的三级亲属 (TDR) 不会增加体重不足/正常先证者的风险，但显着增加了至少有两个 CRC- 超重/肥胖先证者的风险观察到受影响的 TDR；SIR = 1.32（95% CI [1.04, 1.65]）。对于非综合征型 CRC，最大中年 BMI 会影响基于家族史的风险，并应在可能的情况下考虑 CRC 风险。但观察到至少有两个受 CRC 影响的 TDR 的超重/肥胖先证者的风险显着增加；SIR = 1.32（95% CI [1.04, 1.65]）。对于非综合征型 CRC，最大中年 BMI 会影响基于家族史的风险，并应在可能的情况下考虑 CRC 风险。但观察到至少有两个受 CRC 影响的 TDR 的超重/肥胖先证者的风险显着增加；SIR = 1.32（95% CI [1.04, 1.65]）。对于非综合征型 CRC，最大中年 BMI 会影响基于家族史的风险，并应在可能的情况下考虑 CRC 风险。