Supplementary Material for: Body Mass Index and Mortality in Kidney Transplant Recipients: A Systematic Review and Meta-Analysis

<b><i>Background:</i></b> A higher body mass index (BMI) seems to be linked to survival advantage in maintenance hemodialysis patients. However, it is uncertain if this ‘obesity survival paradox' is also observed in kidney transplant recipients. Hence, we systematically reviewed the literature on the impact of pre-transplantation BMI on all-cause mortality in this population. <b><i>Methods:</i></b> We searched MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane CENTRAL for relevant studies up to July 2013. Two investigators independently selected the studies using predefined criteria, abstracted the data from the included studies, and independently assessed each study's quality using the Newcastle-Ottawa Quality Assessment Scale. In addition to the qualitative synthesis, we quantitatively pooled the results of the studies with clinical, methodological, and statistical homogeneity. <b><i>Results:</i></b> We screened 7,123 records, from which we included 11 studies (with a total of 305,392 participants) in this systematic review and 4 studies in the meta-analyses. In the only study that included children, obesity was linked to higher mortality in children of 6-12 years old. For adults, our meta-analyses indicated that compared to normal BMI, underweight [Hazard Ratio (HR): 1.09; 95% Confidence Interval (CI): 1.02-1.20], overweight (HR: 1.07; 95% CI: 1.04-1.12), and obese (HR: 1.20; 95% CI: 1.14-1.23) levels of BMI were associated with higher mortality. <b><i>Conclusion:</i></b> The presence of the obesity survival paradox is unlikely in kidney transplant recipients since both extremes of pre-transplantation BMI are linked to higher mortality in this population.

**背景：** 较高的体重指数（Body Mass Index, BMI）与维持性血液透析患者的生存优势存在关联。然而，这一“肥胖生存悖论”是否同样存在于肾移植受者中，目前尚无定论。因此，本研究针对移植前体重指数对该人群全因死亡率的影响，对相关文献进行了系统回顾。
**方法：** 我们检索了截至2013年7月的MEDLINE、EMBASE、Web of Science、CINAHL及Cochrane CENTRAL数据库，以获取相关研究。两名研究人员按照预先设定的标准独立筛选研究、提取纳入研究的数据，并采用纽卡斯尔-渥太华质量评价量表（Newcastle-Ottawa Quality Assessment Scale）独立评估每项研究的质量。除定性综合分析外，我们还对临床、方法学及统计学特征具有同质性的研究结果进行了定量合并分析。
**结果：** 本研究共筛选出7123条记录，最终将11项研究（总计305392名参与者）纳入本次系统回顾，其中4项研究用于荟萃分析。在唯一一项纳入儿童的研究中，6-12岁儿童的肥胖与更高的死亡率相关。针对成人的荟萃分析结果显示，与正常体重指数相比，体重过低[风险比（Hazard Ratio, HR）：1.09；95%置信区间（Confidence Interval, CI）：1.02-1.20]、超重（HR：1.07；95% CI：1.04-1.12）及肥胖（HR：1.20；95% CI：1.14-1.23）均与更高的死亡率相关。
**结论：** 本研究结果显示，肾移植受者中并不存在肥胖生存悖论，因为该人群移植前体重指数的两个极端（过低与过高）均与更高的死亡率相关。