Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, The Capital Region, Nordre Fasanvej 57, 2000, Frederiksberg, Denmark.
Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Copenhagen, Denmark.
Eur J Epidemiol. 2020 Apr;35(4):347-354. doi: 10.1007/s10654-020-00630-7. Epub 2020 Apr 19.
Body mass index (BMI) has been related to risk of infections. The aim of this study was to assess the shape of the association between BMI and risk of infections and to evaluate whether such associations represent causality. We included 101,447 individuals from The Copenhagen General Population Study who had BMI measured. Outcome was hospital contacts related to infections. The shape of the association between BMI and risk of infections was examined using restricted cubic spline Cox regression. To evaluate causality, we used Mendelian randomization, an epidemiological method that counteracts confounding and reverse causality by using genetic variation as instrumental variables. We created a genetic risk score based on five genetic variants causing lifelong higher BMI and used this score in instrumental variable analysis. During median follow-up of 8.8 years, 10,263 hospital contacts related to infections were recorded. We found a U-shaped association between BMI and risk of any infection and pneumonia, and a linear association between BMI and risk of skin infection, urinary tract infection, and sepsis. In instrumental variable analyses, higher BMI was associated with increased risk of skin infection: odds ratio 1.12 (95% CI 1.03-1.22) for a genetically induced 1 unit increase in BMI. Observationally, low as well as high BMI was associated with increased risk of any infection and pneumonia, whereas only high BMI was associated with increased risk of skin infection, urinary tract infection, and sepsis. High BMI was causally associated with increased risk of skin infection.
体重指数（BMI）与感染风险有关。本研究旨在评估 BMI 与感染风险之间的关联形状，并评估这些关联是否代表因果关系。我们纳入了来自哥本哈根普通人群研究的 101447 名个体，这些个体的 BMI 均有测量。结局是与感染相关的住院接触。使用限制性三次样条 Cox 回归来评估 BMI 与感染风险之间的关联形状。为了评估因果关系，我们使用了孟德尔随机化，这是一种通过使用遗传变异作为工具变量来对抗混杂和反向因果关系的流行病学方法。我们基于导致终生 BMI 升高的五个遗传变异创建了一个遗传风险评分，并在工具变量分析中使用该评分。在中位数为 8.8 年的随访期间，记录了 10263 例与感染相关的住院接触。我们发现 BMI 与任何感染和肺炎的风险之间呈 U 形关联，与皮肤感染、尿路感染和败血症的风险之间呈线性关联。在工具变量分析中，更高的 BMI 与皮肤感染风险增加相关：遗传诱导 BMI 增加 1 个单位，比值比为 1.12（95%CI 1.03-1.22）。观察性研究发现，低 BMI 和高 BMI 均与任何感染和肺炎的风险增加相关，而只有高 BMI 与皮肤感染、尿路感染和败血症的风险增加相关。高 BMI 与皮肤感染风险增加存在因果关系。
