Critical review of the article on ‘Long-term risks for kidney donors’

Citation: Mjøen, G., Hallan, S., Hartmann, A., Foss, A., Midtvedt, K., Øyen, O., … & Holdaas, H. (2014). Long-term risks for kidney donors. Kidney international, 86(1), 162-167.

Introduction

This study aimed to estimate long-term all-cause mortality, cardiovascular mortality, and risk for end-stage renal disease (ESRD) in kidney donors compared with a selected control group screened for eligibility for live-kidney donation.

Follow-up studies of living organ donors have not reported increased cardiovascular and all-cause mortality; however, results may have been confounded by selection bias in the control groups. In most studies, controls were selected from the general population, which includes adults with medical conditions that would make them ineligible as kidney donors (Fehrman-Ekholm et al., 1997; Ibrahim et al., 2009; Mjøen et al., 2012). Hence, these controls would have been less healthy than the living donors and an effect of organ donation on all-cause and cardiovascular mortality could have been underestimated. Additionally, there is a possibility that living donors may be at an increased risk of death for many years beyond the period that has been investigated to date. Thus, an analysis with a longer follow-up period may be necessary to investigate the possible impact of living donor nephrectomy.

The authors conducted a prospective observational analysis among 1901 donors who underwent kidney donation procedures at Oslo University Hospital, Norway, between 1963 and 2007, and followed them up for 15.1 years. Additionally, 32,621 controls were included from the Health Study of Nord-Trondelag (HUNT) population study, constructed to fit the criteria for kidney donation. The median follow-up time for the control group was 24.9 years. Outcome data on all-cause mortality and renal replacement therapy of the donors were determined as of January 2010 and cardiovascular mortality as of January 2008. For controls, all outcome data were determined as of January 2010. No donors were lost to follow-up and causes of death were based on International Statistical Classification of Diseases and Related Health Problems (ICD 10).

During the follow-up period, there were 224 deaths among 1901 kidney donors from the initial inclusion group (30.4%; n=68) which were due to cardiovascular disease. There were 2425 deaths among the 32,621 controls (28.4%; n-688) which were due to cardiovascular disease. A total of nine donors (0.47%) developed ESRD and all of them were family members. Hazard ratio for all-cause death was significantly increased to 1.30 (95% confidence interval 1.11–1.52) for donors compared to healthy controls. There was a significant increase in cardiovascular death to 1.40 (95% confidence interval 1.03–1.91), while the risk of ESRD was significantly increased to 11.38 (95% confidence interval 4.37–29.6). The overall incidence of ESRD among donors was 302 cases per million. Immunological renal disease was the cause of ESRD in the donors. Hence, the final conclusion of the study was that kidney donors are at an increased long-term risk for end-stage renal disease (ESRD), cardiovascular events, and all-cause mortality compared with a control group of non-donors who would have been eligible for donation.

Critique

The title ” Long-term risks for kidney donors’’ accurately summarizes the key focus of this prospective observational study by Mjøen et al. estimating the long-term all-cause mortality, cardiovascular mortality, and risk for end-stage renal disease (ESRD) in kidney donors compared with a selected control group screened for eligibility for live-kidney donation.

This study stands out for its comprehensive approach to investigating the long-term health outcomes of kidney donors compared to a carefully selected control group. One notable strength lies in its extensive follow-up period, spanning several decades, which allows for a more thorough assessment of the risks associated with kidney donation. By including a control group specifically matched to the health status of potential donors, the study minimizes the risk of selection bias, a common concern in previous literature. Additionally, the large sample size, encompassing 1901 donors and 32,621 controls, enhances the statistical power and reliability of the findings. The use of internationally recognized standards (ICD 10) for determining causes of death adds further credibility to the results. Moreover, the identification of immunological renal disease as the primary cause of ESRD among donors provides valuable insights into the underlying mechanisms driving this increased risk. Additionally, the availability of data on key cardiovascular risk factors such as BMI, smoking, and blood pressure in the majority of patients allows for more comprehensive analysis and adjustment for potential confounding variables, further strengthening validity of the study.

However, several limitations should be considered when interpreting the findings of this study. The geographic disparity between the control group, all residing within one county, and the kidney donors drawn from various regions across Norway, introduces a potential source of bias that may limit the generalizability of the results. Additionally, the lack of data on renal function in the control group represents a significant limitation. Because, this information could have provided valuable insights into the observed risks in kidney donors. Furthermore, the longer follow-up time in controls compared to donors may have influenced the detection of ESRD cases, potentially underestimating the true risk faced by donors. Finally, the inability to adjust for the level of education due to missing data highlights a potential limitation in controlling for socioeconomic factors that could impact health outcomes.

Conclusions

In conclusion, this prospective observational study by Mjøen et al. provides valuable insights into the long-term risks faced by kidney donors compared to a carefully selected control group. The comprehensive approach, extensive follow-up period, and large sample size enhance the credibility and reliability of the findings. By meticulously examining all-cause mortality, cardiovascular mortality, and the risk of ESRD, the study highlights important considerations for both donors and healthcare providers. The identification of immunological renal disease as a significant contributor to ESRD among donors underscores the need for continued monitoring and support for this population.

Recommendations

Moving forward, it is important to conduct regular monitoring of renal function and cardiovascular health, as well as ongoing support to address any emerging health concerns among kidney donors. Additionally, research aimed at identifying modifiable risk factors and interventions to mitigate these risks, such as lifestyle modifications and targeted medical interventions, is essential to optimize the long-term health outcomes of kidney donors. Overall, a multidisciplinary approach involving healthcare providers, researchers, and policymakers is necessary to address the complex health considerations associated with kidney donation and to ensure the well-being of individuals who selflessly choose to donate their organs to improve the lives of others.

References

  1. Fehrman-Ekholm, I., Blinder, C. G., Stenbeck, M., Tydén, G., & Groth, C. G. (1997). Kidney donors live longer. Transplantation, 64(7), 976–978. https://doi.org/10.1097/00007890-199710150-00007
  2. Ibrahim, H. N., Foley, R., Tan, L., Rogers, T., Bailey, R. F., Guo, H., Gross, C. R., & Matas, A. J. (2009). Long-term consequences of kidney donation. The New England Journal of Medicine, 360(5), 459–469. https://doi.org/10.1056/NEJMOA0804883
  3. Mjøen, G., Reisaeter, A., Hallan, S., Line, P. D., Hartmann, A., Midtvedt, K., Foss, A., Dahle, D. O., & Holdaas, H. (2012). Overall and cardiovascular mortality in Norwegian kidney donors compared to the background population. Nephrology, Dialysis, Transplantation : Official Publication of the European Dialysis and Transplant Association – European Renal Association, 27(1), 443–447. https://doi.org/10.1093/NDT/GFR303

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