Longitudinal association between dietary protein intake and survival in peritoneal dialysis patients

Decreased dietary protein intake (DPI) may lead to protein-energy malnutrition and may be associated with increased mortality risk. We hypothesized that longitudinal changes in dietary protein intake have independent associations with survival in peritoneal dialysis (PD) patients. 668 stable PD patients were selected in the study from January 2006 to January 2018 and were followed up until December 2019. Their three-day dietary records were collected at the baseline (the sixth month after PD) and thereafter every 3 months for two and a half years. The latent class mixed models (LCMM) were used to identify subgroups of PD patients with similar longitudinal trajectories of DPI. The relation between DPI (baseline and longitudinal data) and survival was examined using Cox model to estimate death hazard ratios. Meanwhile, different formulae were used to assess nitrogen balance. The results showed that baseline DPI ≤ 0.60g/kg/day was associated with the worst outcome in PD patients. Patients with DPI 0.80–0.99g/kg/day and DPI ≥ 1.0g/kg/day both presented positive nitrogen balance; patients with DPI 0.61–0.79g/kg/day presented obviously negative nitrogen balance. Longitudinal association between time-dependent DPI and survival was found in PD patients. The consistently low DPI' (0.61–0.79g/kg/d) group was correlated with increased death risk as compared with the 'consistently median DPI' group (0.80–0.99g/kg/d, HR = 1.59, <i>p</i> = 0.008), whereas there was no difference in survival between 'consistently median DPI' group and 'high-level DPI' group (≥1.0 g/kg/d, <i>p</i> &gt; 0.05). Our study revealed that DPI ≥ 0.8 g/kg/day was beneficial to the long-term outcome for the PD population.

膳食蛋白质摄入量（dietary protein intake, DPI）降低可能引发蛋白质能量营养不良（protein-energy malnutrition），且可能与死亡风险升高相关。本研究假设，膳食蛋白质摄入量的纵向变化与腹膜透析（peritoneal dialysis, PD）患者的生存结局存在独立相关性。本研究于2006年1月至2018年1月期间纳入668名病情稳定的腹膜透析患者，随访至2019年12月。研究基线为腹膜透析术后6个月，此时收集患者的3天膳食记录，随后每3个月收集1次，持续两年半。本研究采用潜类别混合模型（latent class mixed models, LCMM），识别出具有相似膳食蛋白质摄入量纵向变化轨迹的腹膜透析患者亚组。采用Cox模型（Cox model）分析膳食蛋白质摄入量（基线及纵向数据）与患者生存的相关性，以估算死亡风险比。同时，采用不同公式评估患者的氮平衡状态。结果显示，基线膳食蛋白质摄入量≤0.60g/kg/天的腹膜透析患者预后最差。膳食蛋白质摄入量处于0.80~0.99g/kg/天及≥1.0g/kg/天的患者均呈现正氮平衡；而摄入量处于0.61~0.79g/kg/天的患者则呈现明显的负氮平衡。本研究发现，随时间变化的膳食蛋白质摄入量与腹膜透析患者的生存结局存在纵向相关性。与‘持续中等膳食蛋白质摄入量组’（0.80~0.99g/kg/天，风险比（hazard ratio, HR）=1.59，*p*=0.008）相比，‘持续低膳食蛋白质摄入量组’（0.61~0.79g/kg/天）的死亡风险显著升高；而‘持续中等膳食蛋白质摄入量组’与‘高膳食蛋白质摄入量组’（≥1.0g/kg/天，*p*>0.05）的患者生存结局无显著差异。本研究表明，膳食蛋白质摄入量≥0.8g/kg/天对腹膜透析患者的长期生存结局具有获益作用。