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

Abstract

Background

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.

Methods

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.

Results

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, p = 0.008), whereas there was no difference in survival between 'consistently median DPI' group and 'high-level DPI' group (≥1.0 g/kg/d, p > 0.05).

Conclusion

Our study revealed that DPI ≥ 0.8 g/kg/day was beneficial to the long-term outcome for the PD population.

Keywords:

• Malnutrition
• daily protein intake
• peritoneal dialysis
• survival
• nitrogen balance

Acknowledgements

The authors would like to express their appreciation to the patients and staff of PD center in Peking University Third Hospital for their participation in the study.

Ethics approval and consent to participate

The study was approved by the Medical Ethical Committee of Peking University Third Hospital (IRB2021-516-02). Informed consent was waived because of the retrospective design of this study.

Consent for publication

Not applicable.

Author contributions

Shu-Hong Bi, Chunyan Su and Baohua Li designed the study. Shu-Hong Bi and Xiaoxiao Wang took responsibility for the content of the manuscript, including the data and analysis. Chunyan Su, Wen Tang, and Tao Wang helped to review and revise the manuscript. All of the authors have approved the submitted version.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data are not available due to the property rights of the healthcare center that has collected these data. Chunyan Su could be contacted if someone wants to request the data.

Additional information

Funding

The present work was financially supported by the Beijing Health Technologies Promotion Program (BHTP P202058), the Health Human Resources Development Center of National Health Commission (2019-HLYJ-018), the PKU Baidu fund (2020BD030), and Key Clinical Projects of Peking University Third Hospital (No. BYSYZD2019039).