Optimizing Kidney Allocation: LYFT for LIFE

Under the current system, kidneys are allocated to patients primarily based on the time that the patient has been on the waiting list and the quality of the match.  If we evaluate these criteria "locally" there's nothing obviously wrong but if we step back and think globally, that is think about what the ultimate goal of the transplant system should be, then the current system is deeply misguided.  Suppose that we want the transplant system to maximize total life expectancy or, as it is known in the literature, to maximize the life-years from transplant (LYFT).

The current system does not maximize life expectancy.  In the current system, a 60 year old patient can be given a 20 year old kidney–that's a waste because the life expectancy of the kidney is longer than that of the patient; it's like putting a new clutch in a car that is rusting away.  If we had 20 year-old kidneys to spare, this wouldn't be a big problem.  But we don't have 20-year old kidneys to spare, so we also give 20-year old patients 60-year old kidneys which means the kidney is likely to die early taking the patient along with it.  If we want to maximize total life expectancy, younger people should get younger kidneys.

Here is a simple example to illustrate the principle.  Suppose that the life expectancy of both patients and kidneys is 75 years of age so everyone dies when they are 75 or when their kidney is 75, whichever comes first.  Thus, if we allocate the 20 year old kidney to the 60 year old patient and vice-versa we gain a total of 30 years of life expectancy.

Patient Age Life Years
20 60 15
60 20 15
30 years Total

But if we allocate the 60 year old kidney to the 60 year old patient and the 20 year old kidney to the 20 year old patient we more than double life expectancy to 70 years in total.

Patient Age Life Years
60 60 15
20 20 55
70 years Total

It's not just age that matters, it turns out that the longer a patient has been on dialysis the less is their life expectancy after transplant (dialysis stresses the body so the sooner we get someone a transplant the better).  Although it may seem unfair, if we want to maximize total life expectancy we are doing the wrong thing by giving more points to patients who have been on the list longer.  

An optimized allocation system that took into account these considerations would increase total life
expectancy (modestly but significantly, about 11,500 extra life years) but it wouldn't benefit every individual.  Maximizing life expectancy would shift organs away from older people and people who have been on the waiting list a long time towards younger people.  As a result, some patients have argued that LYFT is unfair.  The Office of Civil Rights is even asking whether LYFT might violate age discrimination laws.  

But consider, would the older patients have objected to LYFT when they were younger?  If not, shouldn't their objections be discounted?  More formally, consider how people would vote behind a veil of ignorance.  By definition a LYFT approach maximizes total life expectancy, so without knowing the specifics of who you are or when you might need a transplant it's likely that behind a veil of ignorance just about everyone would favor LYFT.  Thus, in my view LYFT is a fair and ethical system. 

Here are previous MR posts on kidney transplant policy.


The codgers are the people who have put money into the pot to pay for the whole system, the youngsters are people who have, as yet, only drawn out of the pot. Treat the codgers say I, albeit not wastefully.

cue the obligatory slippery slope argument: should then all scarce health care resources be allocated according to age?

I'm not a physician and not an expert on these matters, but this is assuming that the body will accept the kidney as if it was the original kidney, with no problems over the long term. Don't kidneys transplanted have a different lifespan in the body of a recipient than the ones we are born with? i.e., a kidney from someone who donated at death is thought to last shorter in the body of a recipient than that of a living person who is not a family member, and that one lasts less, on average, than that of a sibling.

What that seems to indicate is that once transplanted, even if the transplant is successful and the body accepts the transplanted kidney well, over the long term, there might still be certain level of gradual "rejection" or reaction of the body to the foreign organ that makes the life expectancy of such organ be less than that of a healthy organ with which the body was born. If that is the case, wouldn't that alter the numbers, meaning on average the life expectancy of the transplanted kidney on a recipient body might be less -- and perhaps considerably less -- than that of human life expectancy?

Another idea: more medical research to figure out ways to stop so many kidneys from failing in the first place.

"The codgers are the people who have put money into the pot to pay for the whole system,"

Old people invented kidneys?

anon and dale,

It doesn't matter. The important point is that resources are allocated the traditional Communist Russia way, waiting in lines. The point is to not do it that way.

dearieme brings up a good point that I rarely ever see discussed, that of generational finance, and you can thank the welfare state for the upcoming reduction in loyalty to oldsters. What does the younger generation actually owe the oldsters? I think it's a great debate, but irrelevant here. The medical industrial complex simply acts as a gatekeeper and rent seeker on the kidney market.

Or we could just move to opt-out instead of opt-in and pretty much take care of most organ shortages.

The real problem with most charity is that our refusal to put prices on life make our spending wildly inconsistent - we leave low hanging fruit all the time...

I don't want to talk about kidneys but about a broader topic, generational finance or generational solidarity like the Germans would call it. The question is if aging societies will break the back of the young. In Germany, pensioners and retiress live relatively well compared to young unskilled workers and children. Whereas the old people in Germany enjoy their lush pensions, the schools are crumbling and something like 50% of children live in poverty, compared to only 10% of retiress. Like I already said, retiress enjoy higher incomes than a lot of workers in Germany. Because retirees are increasing in numbers and tend to vote, they enjoy a lot of entitlements, paid by the young. But retirees are increasing, so this system can't be maintained. Some young Germans even can't afford children because they pay so much taxes to the elderly. In the USA the situation isn't so different however: the babyboomers with their huge entitlements are already breaking the back of California. This problem can not be solved through inmigration of low skilled and low educated workers. These workers only aggravate the problems.

Seconding anon with his pesky real world data: another factor to consider is that a sizable number of kidney failures are the result of Type I diabetes, with its attendant stresses to the body. To wit, a sizable number of kidney transplants are done simultaneously with pancreas transplants, and if possible, BEFORE kidney failure.


Also, keep in mind that a single kidney is more than enough to handle the needs of a person adhering to a healthy diet. While a live donor can give only one kidney and live, a corpse can donate two kidneys AND a pancreas (among other tasty items). A well-coordinated donor queue in a densely populated area could conceivably kill two birds with one stone, so to speak.

By the way, before dialysis, those people would be dead. So, it's interesting that time on dialysis is viewed as a kind of payment by the 'victims'.

I think this is a pretty dangerous proposition. Why just stop at age then? Why not maximize the total "productive potential" rather than just "life years"? Therefore put a smart, high-IQ 20-year old ahead in the list. Perhaps the most optimal way then would be to just let people on the list bid for kidneys? Shouldn't the person with maximum utility for the kidney be the one who will bid highest?

Furthermore why stop at kidneys? The entire health-care system could be redesigned with a bias towards the young. Say in an ER room the triage could be designed to push ahead the younger. And while we are at it we might as well get rid of all hospice care. For the goal of life-year maximization a hospice is a very low yield activity.

It is a very slippery slope indeed. There have to be (a few) areas where we make our decisions not on the basis of economic utility alone.

A soda and salt tax plus universal health care could eliminate an awful lot of the need for transplants.

Carnegie Mellon used to have a class on decision sciences that had the students break up into groups to determine allocation rules for donated kidneys to a collection of patients. We were provided with detailed medical files, personal histories, family records, etc.

After much brow-beating of my fellow group members, we randomized.

It may not "feel" right, but no one could claim unfair.


And, what about second order effects of the LYFT decisions? Young guy who dies with kidney failure may have (I don't know) excellent organs to donate to others. He sure doesn't like that LYFT calculation!

Everybody always mention mickey mantle but not pat summerall or steve jobs who has cancer as well there is no differance with any of them???

This is academic. Most donated kidneys do not last 10 years, regardless of whether they are from older or younger people.

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