Even after reform, women remain 16 percent less likely to receive a lung transplant.
In the quiet arithmetic of organ allocation, a woman's chance at survival remains measurably smaller than a man's — not by intention, but by the collision of biological reality and institutional design. UCLA Health researchers have found that despite a landmark 2023 overhaul of the national lung transplant distribution system, women are still 16 percent less likely than men to receive a transplant, down from a 32 percent gap before the reform. The progress is real, but it is not justice. What the findings ask of medicine is an older and harder question: how do we build equity into systems where nature itself has not distributed its burdens equally?
- Women awaiting lung transplants face a compounding disadvantage — smaller bodies mean fewer compatible donors, and immune systems sensitized by pregnancy or transfusions narrow the window of viable matches even further.
- A 2023 policy overhaul added height, blood type, and immune sensitivity to transplant scoring, signaling a genuine institutional reckoning with gender disparity in organ access.
- The reform cut the transplant gap nearly in half — from 32 percent to 16 percent — but UCLA researchers warn that halving an injustice is not the same as ending it.
- Women on waiting lists today are still losing ground to a system that has improved but not caught up to the full complexity of their biological circumstances.
- Researchers are now pressing for further algorithmic refinements, framing the challenge as one of moral design: acknowledging biological difference without allowing it to calcify into permanent disadvantage.
A woman waiting for a lung transplant faces odds that her male counterpart does not. That is the sobering conclusion of UCLA Health researchers led by Dr. Abbas Ardehali, who examined how a major 2023 policy reform intersected with the biological realities that shape women's access to donor organs.
The findings are a study in partial progress. Before the Organ Procurement and Transplantation Network introduced its new Composite Allocation Score in March 2023, women were 32 percent less likely than men to receive a lung transplant. After the reform, that figure fell to 16 percent. The new system, which incorporated height, blood type, and immune sensitivity into its matching calculations, moved the needle — but did not move it far enough.
The barriers are rooted in biology. Women's smaller average body size limits the pool of physically compatible donor lungs. Their immune systems, more frequently sensitized through pregnancy, transfusions, or autoimmune conditions, are more prone to rejecting foreign tissue. Together, these factors mean a woman is not simply waiting for lungs — she is waiting for a rare convergence of size, blood type, and immunological compatibility.
For nearly two decades, the previous Lung Allocation Score system prioritized patients by medical urgency alone, blind to these compounding disadvantages. The 2023 reform was a meaningful correction, but Ardehali and his colleagues, publishing in the Annals of Thoracic Surgery, argue it remains insufficient.
What the research ultimately demands is a harder kind of design work: building fairness into a system where the underlying biology does not distribute its burdens equally. Ardehali has called for continued refinements to the scoring algorithm — adjustments that acknowledge biological difference without allowing it to become a permanent justification for unequal access to life-saving care. For the women currently on transplant waiting lists, that work cannot come soon enough.
A woman waiting for a lung transplant faces odds that a man in her same condition does not. This is the finding from UCLA Health researchers who examined what happens when policy changes meet biological reality in the world of organ allocation.
Dr. Abbas Ardehali, who directs the heart, lung, and heart-lung transplant programs at UCLA Health, and his team discovered something sobering: even after the nation overhauled its organ distribution system in 2023, women remain significantly less likely than men to receive the lungs they need to survive. The gap has narrowed, but it has not closed. Before the policy change, women were 32 percent less likely to get a transplant. After it, they were still 16 percent less likely. That is progress, but it is not equity.
The reasons are rooted in biology and history. Women typically have smaller bodies, which means fewer donor lungs will physically fit. Their immune systems, shaped by pregnancies, blood transfusions, or autoimmune conditions, are more likely to develop antibodies that reject foreign tissue. These two factors alone shrink the pool of compatible organs dramatically. A woman waiting for a transplant is not just waiting for any lungs—she is waiting for lungs from a donor whose size, blood type, and immunological profile align with her own narrow window of compatibility.
For nearly two decades, the Lung Allocation Score system, introduced in 2005, tried to solve this problem by prioritizing patients based on medical urgency. But it did not account for the biological differences that affect women disproportionately. In March 2023, the Organ Procurement and Transplantation Network introduced a new system called the Composite Allocation Score. It added height, blood type, and immune sensitivity to the calculation, attempting to match donors and recipients more precisely.
The new system did help. The 16-percentage-point improvement from 32 percent to 16 percent represents real lives—women who would not have received transplants under the old rules but did under the new ones. Yet Ardehali and his colleagues, whose findings appear in the Annals of Thoracic Surgery, concluded that the improvement, while meaningful, is not enough. The system still leaves women at a significant disadvantage.
What happens next matters. Ardehali said further refinements to the scoring algorithm are necessary. The challenge is not simple: the system must account for biological realities without hardening them into permanent barriers. It must recognize that a woman's smaller body size is a fact, not a flaw, while also ensuring that this fact does not become an excuse for unequal access to life-saving treatment. The researchers are essentially asking: how do we build fairness into a system where the biology itself is not fair?
This is not a problem that will solve itself. It requires continued attention, continued research, and continued willingness to adjust the rules when evidence shows they are not working. For the women on transplant waiting lists right now, the stakes could not be higher.
Notable Quotes
There was a modest improvement in narrowing the gap, but we still have a lot of work to do. Further refinements to the scoring system are needed to ensure a fair and effective organ allocation system for all patients, regardless of gender.— Dr. Abbas Ardehali, director of UCLA Heart, Lung, and Heart-Lung Transplant Programs
The Hearth Conversation Another angle on the story
Why does body size matter so much in lung transplants? Can't surgeons make adjustments?
A lung has to fit inside a chest cavity. If the donor lungs are too large, they won't fit. If they're too small, they won't provide enough function. There's a physical constraint that no amount of surgical skill can overcome.
And the antibody issue—that's from pregnancy?
Pregnancy is one source, but also blood transfusions, previous transplants, or autoimmune diseases. Women are statistically more likely to have developed these antibodies, which means their immune system will attack a donor organ more aggressively.
So the new system in 2023 was supposed to fix this?
It helped. It added those factors into the calculation. But the researchers found that even accounting for them, women still get transplants at lower rates. The system is better, but it's not equal yet.
What would equality look like?
That's the hard question. You can't change biology. But you can keep refining how the system weighs different factors. Maybe there are other variables no one has thought to measure yet.
Is this a problem unique to lungs?
No. Other organs have similar disparities. But lungs are particularly acute because of the size constraint and the immune sensitivity issue. It's a concentrated version of a broader problem in transplant medicine.