Geriatric nephrology is on the rise as the baby boomers age, and more and more patients will encounter nephrologists. Transplant nephrology is facing this challenge as well. A recent study was published in the American Journal of Kidney Diseases on advanced age and kidney transplantation, and the corresponding author Dr. Kamyar Kalantar-Zadeh (KK) from the University of California, Los Angeles, spoke with Dr. Vinay Nair (eAJKD), eAJKD advisory board member, about his findings. This is the first part of the interview; the second will post later in the week.
eAJKD: Would you please give us a summary of your study?
KK: In this epidemiologic analysis, we examined the outcomes of 145,000 kidney transplant recipients across all age groups. In particular, we focused on the outcome of the transplant in individuals over 65, by dividing them into three subgroups. We examined the type of the donor and kidney transplant applicants to determine whether advanced age was a major factor.
eAJKD: In your paper, elderly patients had significantly higher mortality than younger patients, but nonetheless benefitted from transplantation. Based on this observation, do you think there should be any age cut off for transplantation or for referral to transplantation?
KK: In fact, that was the main driving force behind conducting this study. We questioned whether there should be an age threshold where transplant candidates should be considered low or “off” the list. What we found is that across all age groups, including the advanced ages, there was a favorable outcome, notwithstanding the fact that being elderly is inherently associated with increased mortality and poorer outcomes. Based on prior studies and ours, no age cut off should be recommended.
eAJKD: What are your thoughts on the very elderly (above age 75)?
KK: Yes, that was indeed a main focus of this study. Very few people older than 75 receive kidney transplants in this country. Out of 145,000 individuals over the time of this cohort, approximately 1% percent of the recipients were 75 years or older. In our study, over 1200 kidney recipients were 75 years or older. This is a relatively significant number indicating that there are centers that have been offering kidneys to these advanced aged candidates.
eAJKD: I also noticed that in most age groups, extended criteria donor (ECD) use was associated with a higher mortality compared to non-ECD use. Why do you think this association was not present in elderly patients over 70 years of age?
KK: There are several hypotheses, but I think the most likely one is individuals who are 75 years or older inherently have shorter life expectancy. Therefore, differences in mortality become less relevant when life expectancy is shorter. Otherwise, ECD was associated with a favorable outcome across other age groups (younger than 75). Whether or not other biologic factors play a role remains to be seen.
This is clinically relevant because if the data indicates that individuals older than 75 may not benefit significantly from non-ECD donors, then there would be a more flexible view towards offering ECD kidneys to these individuals rather than allowing these ECD kidneys to be wasted.
eAJKD: ECD use was also associated with a higher risk of death-censored graft failure compared to non-ECD use, but that association was not present in elderly patients over 70 years of age. Do you think this is because the life expectancy is shorter in the elderly?
KK: Yes, that probably plays a major driving force here, even though we should also qualify our study for its potential limitations including a more restrictive sample size of those individuals with advanced age above 75. Nevertheless, our study was one of the few studies which looked at over 1,000 recipients aged 75 years or higher.
That means even though we see a trend, the graft survival difference of ECD and non-ECD tends to mitigate with advancing age to the point that above 75 there has been no advantage in offering non-ECD. This is limited to comparing ECD versus non-ECD within deceased donors.
eAJKD: Do you think that the elderly recipients’ immune system, being weaker at older age, plays a role in the better outcome of ECD kidneys?
KK: It was discussed among co-authors that the immunologic constellation of advanced age could have played a role. Even with reduced life expectancy, the immune system and tolerance-related factors could have played a role as well.
eAJKD: It may be interesting to compare the outcome or graft survival of ECD kidneys in different strata of age groups. For example, in the 70-year-olds with ECD kidneys, do the grafts actually last longer than in younger individuals?
KK: We have been looking at that question: preliminary data suggests that graft survival may not be significantly different across age groups, especially when comparing advanced age groups with each other (comparing subgroups of 65 and higher).