Why do women make up a majority of live organ donors but not of organ recipients?

Several Studies Do Find Women Predominate Among Living Organ Donors

Studies ranging from Germany (1) to Oman (2) find that among medically suited living donors, women tend to donate more than men.

Kidney: In 2005, 59.2% of living US kidney donors were women while 58.2% of kidney recipients were men (3). Predominance of female kidney donors is seen not just in the US but also in Brazil (4). Global estimates for living kidney donors is ~65% female with ~65% of kidney recipients being male (3). Spousal differences are more striking compared to generic estimates. A University of Michigan study found 69% of spousal donations were female (5).

Liver: In 2005, 58.3% of living US liver donors were women while 58% of living liver segment recipients were men (6). Again, spousal differences are more striking compared to generic estimates. A Canadian study found 36% of women suitable for donating to their husbands were willing to do so while only 6.5% of suitable husbands were willing to be donors for their wives (7).

Examination of published literature suggests a combination of

• Different solid organ disease prevalence rates between men and women,
• Greater cultural pressure on women to carry the burden of caregiving,
• Gender selection bias in the healthcare system,

all of these factors contribute to why women predominate in living organ donations and yet receive fewer organ transplants.

Different solid organ disease prevalence rates between men and women

Several studies have documented pronounced gender bias in transplantation. However, while examining these, onus is on us to account for gender-based disease prevalence rate differences, especially where the rates are higher in men.

Kidney: Renal disease tends to be more common in men compared to women (8). Mortality rates of men on dialysis is also higher compared to women (9). Speculation is baseline creatinine clearance is better in elderly women compared to men.

Heart: In 1996, 81.2% of US heart transplant recipients were men and this only decreased to 76.8% by 2005 (6). Part of this has to do with greater preponderance of coronary artery disease in young men compared to young women. Even among those aged 55 to 64 years, congestive heart disease rates in US men are twice those in women.

Liver: Liver disease rates are higher among US men (10).

Greater cultural pressure on women to carry the burden of caregiving

Studies suggest women may offer kidneys more often from a greater drive to alleviate suffering and/or a greater inability to resist subtle pressures (11). Some authors speculate preponderance of bearing the burden of caregiving in a family may extend the woman's role to becoming a living kidney donor (12). Some studies support this conclusion (13). In fact, women are considered more vulnerable and more easily persuaded/pressured to donate (14). This is the reason the multi-disciplinary living donor assessment process in Australia and the US focuses on the living kidney donor's autonomy and decision making in the absence of coercion (15). Cultural differences may also play a role. Even today, in many societies the woman is the main caregiver with the man the breadwinner. When a woman undergoes transplantation, the man would need to take time off work to take over household management. Some authors (3, 12) speculate transplant centers may inadvertently reinforce such gender roles in the manner they offer, discuss and foster women's access to transplantation.

Gender selection bias in the healthcare system

Studies find men are often preferentially placed on transplant waiting lists (16, 17).

Kidney: A French study on 9497 men and 5386 women on dialysis found that women had both a lower probability of being registered on the waiting list and waited longer after starting dialysis before being registered (18). This study found older, unemployed and diabetic women were more likely to be victims of such disparities. A large southeastern US study found women were less likely to be perceived suitable for kidney transplants compared to men, and this was independent of medical factors (19). Gender bias favoring men was found in other US studies as well (20, 21).

Heart: Of US heart transplants in 2005, 52.3% of heart transplant recipients in 2005 were aged 50 to 64 years and 10.3% >65 years. With age, especially >65 years, coronary artery disease rates between US men and women are similar (22). Yet, gender bias persists even among this older age group of heart transplant recipients (3). Studies show that women decline heart transplantation at greater rates compared to men (23). One reason proffered for this implies surgeons prioritizing vanity over vocation, i.e., women presented with this option in a manner inclined to discourage them for the simple reason that post-transplant mortality rates tend to be higher for women compared to men, and heart transplant surgeons may be motivated by concern for their success rates (3).

Liver: One US study found women were less likely to get liver transplants (24) while another one found twice as many men as women get liver transplants (25) even though disease rates aren't twice higher.

According to JoAnn Grif Alspach (26), gender bias in medical care can thus be the unintentional product of implicit, insidious bias in the culture of medicine itself. She then lists the following implicit cultural biases as possible reasons,

'• Underestimating or misunderstanding a woman’s risk for health problems or complications 8

• Differences in the way women experience (cardiac) symptoms 30

• Differences in the way women perceive themselves and their illness 30

• The most likely explanations are at the patient level, the physician level, or both. Patients may have misperceptions of indications, risks, or benefits of surgery.

• One factor may be the differences in style that women and men use to describe their symptoms or injuries to the physician. Women tend to describe what they experience as a more personal, narrative commentary compared to men, who typically describe symptoms in a more straightforward, factual manner with fewer comments. 49 Women’s narrative presentation style reportedly contributed to physicians making more diagnostic errors in their evaluations of chest pain in women. 50

• Unconscious prejudices among physicians—social stereotyping 29

• Overt discrimination based on sex. Some physicians take women’s symptoms less seriously, attribute symptoms to emotional rather than physical causes, and refer women less often than men for specialty care, even women with a relatively greater degree of disability. 29

• Cultural biases, especially among older male physicians 51

• Women thinking of stroke and heart disease as men’s diseases 51

• Perceived differences in injury severity or perceived benefits of trauma center care, or from subconscious gender bias 48'

Ironically, transplants in women have also often been pioneering.

• In August 1966, Dr. Michael E. DeBakey implanted the 1st extracorporeal left ventricular assist device in a 37-year old woman who couldn't be weaned from bypass following a double valve replacement (27). The pump was successfully removed after 6 days and she survived for 6 years with good cardiac function only to tragically die from an automobile accident.
• The 1st pancreas allograft occurred on December 17, 1966 at the University of Minnesota when Drs. William Kelly and Richard Lillehei simultaneously transplanted a kidney allograft plus a duct ligated segmental pancreas into a 28 year old woman (28).

Gender Bias Matters Medically Because Gender Mismatch In Transplants Is Often Counter-Productive

Gender mismatch between donors and recipients is often counter-productive. Specifically, men with allografts from women have greatest risk of long-term allograft failure (29). This is especially true for kidney transplants (30).  Risk also runs both ways. In donations after circulatory/cardiac death (DCD), transplanting a male liver into a female recipient is a risk factor for primary non-function (31). Female recipients of male hearts is a risk factor for acute cellular and antibody-mediated rejection of heart transplants (32, 33, 34, 35, 36). Studies suggest gender matching may protect against heart transplant rejection (37).

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