Long-term mortality of living kidney donors: a systematic review and meta-analysis

Background To date, several studies have reported inconsistent findings regarding the mortality risk faced by living kidney donors and controls. Our study assessed the methodological quality of previous studies and performed an updated meta-analysis of the mortality risk. Methods Comprehensive literature searches were conducted involving the PubMed, Embase, and Cochrane databases through September 2020. The search terms used included 'living donor' and 'kidney transplantation' and 'kidney donor' and 'mortality' or 'death' or 'survival'. We evaluated the risk of bias in such studies using ROBINS-I tool. Mortality risk was analyzed using OR and HR. Results The qualitative review involved 18 studies and the meta-analysis included nine studies. We identified 3 studies with an overall risk of bias rated as "Low", 2 studies rated as "Moderate", 8 studies rated as "Serious", and 5 studies rated as "Critical". The pooled overall mortality risk in the meta-analysis was 0.984 (95% CI: 0.743, 1.302). In the subgroup analysis of HR and OR, the summary effect estimates did not reach statistical significance. The meta-regression analysis revealed that the donor group of more than 60,000 (1.836, 95% CI: 0.371, 6.410) carried a significantly high mortality risk compared with the donor group of less than 60,000 (0.810, 95% CI: 0.604, 1.086) (P = 0.007). The number of total patients was associated with slightly elevated mortality risks (0.796 for < 10,000, 0.809 for 10,000-60,000, and 1.852 for > 60,000; P < .054). Conclusions Current evidence based on this systematic review suggests that the methodology of previous studies was inconsistent and also carried a high risk in several aspects. Updated meta-analysis showed that the mortality risk was not significantly different. Future studies with well-designed methodology are necessary.