Awareness of Legislation Moderates the Effect of Opt-Out Consent on Organ Donation Intentions

Abstract

Background 

With the worldwide shortage of organs to meet the demand for transplants, many countries are considering whether introducing opt-out consent would increase the availability of donor organs. This research assessed whether people’s willingness to donate their organs for transplant purposes was greater in opt-out than opt-in countries and whether such effects were moderated by people’s awareness of their nation’s legislative system.

Methods 

Using secondary data from the 2010 Eurobarometer (n=29,288), this study compared people’s willingness to donate their organs in a representative sample from 19 opt-out and 10 opt-in consent countries from across Europe.

Results 

The majority of participants (66.04%) stated that they were willing to donate their organs for transplant purposes. The proportion of people who were willing to donate their organs did not differ between opt-in (65.97%) and opt-out (66.37%) countries. However, the effect of consent on willingness to donate was moderated by people’s awareness of their nation’s organ donation legislation. When people were aware of their nation’s legislation, the proportion of people who were willing to donate their organs was greater in opt-out (85.26%) than opt-in (80.72%) countries. By contrast, when people were not aware of their nation’s legislation, there was no difference in people’s willingness to donate their organs in opt-in (58.63%) and opt-out (59.23%) countries.

Conclusions 

Opt-out consent countries should increase people’s awareness of their legislation to improve donor rates. Further research is needed to understand the factors that moderate the effect of opt-out consent legislation on organ donation.

In Brief

Supplemental digital content is available in the article.

In the majority of countries in the world, there are an insufficient number of donor organs to meet the demand for transplants. In the United States, there are currently more than 110,000 people on a waiting list for a solid organ transplant and 18 people per day die waiting for an organ (¹). Similarly, in the United Kingdom, there are more than 10,000 people waiting for a solid organ transplant and 3 people die per day awaiting a transplant (²). To make matters worse, the number of people joining transplant waiting lists has increased year-on-year (^{3, 4}). There is therefore an urgent need to increase the number of posthumous organ donors. One strategy that has been implemented in numerous countries across the world is to change the legislative system from opt-in to opt-out consent. In opt-in consent systems, people are required to consent to organ donation before they die in order for their organs to be donated. This usually involves registering as an organ donor or carrying a donor card. By contrast, in opt-out consent systems people must state that they object to donation before they die to prevent their organs from being transplanted. In the majority of opt-out consent systems, family members are required to give permission on the deceased’s behalf in order for donation to occur (⁵).

Numerous reasons have been suggested to explain why opt-out consent legislation should lead to increased organ transplant rates. First, opt-out consent legislation may bridge the gap between people’s intentions and their actual behavior by removing the need to undertake any actions to become an organ donor (⁶). Opt-out consent legislation may also increase people’s willingness to donate by altering their beliefs regarding policymaker’s recommendations (⁶). Indeed, research has found that when the default was to be an organ donor (such as in opt-out consent countries), people believed that policymakers recommended that they should become donors (⁷). By contrast, when the default was not to be a donor (such as in opt-in countries), people believed that policymakers do not recommend donation (⁷). Third, people may regard default options as societal norms and act accordingly (⁸). Finally, organ donation may be regarded as more meaningful and important in opt-out than opt-in countries (⁹). In support of these rationales, the number of deceased donors whose death has been confirmed by brainstem testing (donors after brain death) is greater in opt-out than opt-in consent countries (^{6, 10–13}). Moreover, donation after brain death rates increase after the introduction of opt-out consent (^{14, 15}).

It could therefore be concluded that the introduction of opt-out consent legislation is likely to increase the number of posthumous organ donors. However, because this research is observational rather than experimental, researchers cannot establish a causal relationship between opt-out consent legislation and donor rates. Indeed, critics of opt-out consent (^{16, 17}) have argued that many other factors may be responsible for these effects. For example, Fabre et al. (¹⁶) argue that the increase in Spain’s organ donation rates occurred 10 years after the introduction of opt-out consent and suggest that the major catalyst for Spain’s high donation rate is the introduction of what is now known as the “Spanish Model”. This involved operationalizing a transplant coordination network that operated at different levels (hospital, regional, and national levels), placing transplant coordinators at each procurement hospital, and improving the level of information received by the general public (for full details, see (¹⁸). In keeping with this argument, in 2008, the UK Organ Donation Taskforce concluded that there was insufficient evidence to suggest that opt-out consent legislation would cause an increase in the number of organs donated (¹⁹).

An alternative hypothesis that can be drawn is that the factors that were varied by the introduction of the “Spanish Model” may moderate the effect of opt-out legislation on organ donation. For example, improving the amount of information received by the general public may have increased their awareness of their nation’s legislation. Although it may appear self-evident that the majority of people should know their nation’s consent legislation, a recent survey found that only 27% of Europeans were aware of this (²⁰). As mentioned above, opt-out consent legislation is likely to increase people’s willingness to donate their organs by altering their beliefs about policymaker’s recommendations, societal norms, and the importance of donation (^{6–8, 10}). These effects are only likely to occur when people are aware of their nation’s legislative system. When people are unaware of their nation’s consent law, they cannot use this information to guide their decision about donating their organs. Indeed, research has found that the effect of opt-out legislation on organ donation intentions is moderated by people’s awareness of their nation’s legislative system (²¹).

Although the Mossialos et al. (²¹) research is promising, the survey only collected data from western European countries. Eastern European countries are generally more reluctant to donate their organs than their western European counterparts (²⁰). It is therefore unknown whether such effects would be replicated when eastern European countries are also included into the analysis. The present study enhanced this research by assessing eastern and western Europeans. According on Mossialos et al. (²¹), we hypothesized that opt-out consent would only increase people’s willingness to donate their organs when they were aware of their nation’s legislation. This was assessed using secondary data analysis of the Eurobarometer that was conducted in 2009 (²⁰). This survey was undertaken in 27 European Union member states and 3 candidate states (Croatia, Turkey, and Macedonia). A representative sample of the population was obtained from each country (for full details, see SDC, https://links.lww.com/TP/A782).

RESULTS

In line with previous research (²²), participants from Turkey were removed from the data, before further analysis, because consent legislation is inconsistent across this nation. The remaining study sample consisted of 29,288 participants (12,988 men and 16,300 women) from 29 European countries. Participant’s ages ranged from 15 to 98 years (mean [SD], 48.27 [18.45]; for a summary of the demographics, see Table 1).

TABLE 1: Demographics of the sample

Individual-Level Variables

The 2010 Eurobarometer measured people’s willingness to donate their organs (yes vs. no), whether people had discussed organ donation with their family (yes vs. no), and whether they were aware of their nation’s organ donation legislation (yes vs. no). The majority of people were willing to donate their organs (Table 2). The vast majority of people were not aware of their nation’s organ donation legislation. Moreover, the majority of participants had not discussed the topic of organ donation with their family.

TABLE 2: Percentage of yes and no responses for the organ donation variables

National-Level Variables

There were more opt-out (n=19) than opt-in (n=10) countries. In line with previous research (^{10, 22}), three national-level variables were entered into the analysis: GDP, legal system, and proportion of Catholics. These variables were included to ensure that they were not responsible for the hypothesized effects (for more details, see Materials and Methods). GDP did not vary between opt-in and opt-out countries (Table 3). Moreover, there was not a significant association between consent system and (a) legal system and (b) Catholicism.

TABLE 3: Relationship of consent system to the national variables (GDP, legal system, and Catholicism)

Willingness to Donate Organs

When people were not aware of their nation’s organ donation legislation, there was little difference in the proportion of people who were willing to donate their organs in opt-in (58.63%) and opt-out (59.23%) consent countries (Fig. 1). By contrast, when people were aware of their nation’s legislation, a greater proportion of people were willing to donate their organs in opt-out (85.26%) than opt-in (80.72%) consent countries. These results imply that opt-out consent may only increase people’s willingness to donate their organs when people are aware of their country’s legislation. This rationale was tested using multilevel modeling.

FIGURE 1: Proportion of people who were willing to donate their organs in opt-in and opt-out countries for people who were aware and unaware of their nation’s legislation.

Multilevel binary logistic regression was used because (a) participants were from (or nested within) different countries and (b) the outcome variable (willingness to donate) was categorical (yes vs. no). The key predictor variables were the main effects consent legislation (opt-in vs. opt-out) and people’s awareness of their nation’s legislation and the interaction between these two variables. The main effect of discussing donation with one’s family and the interaction of this variable with consent was also included in the analysis to ensure that these variables were not responsible for any effects of the key interaction (consent by awareness of legislation). GDP, legal system, and Catholicism were entered into the model as covariates to control for these national-level variables. Age, gender, and level of education were also entered into the model because previous research has suggested that these variables may predict people’s willingness to donate their organs (^{21, 23, 24}). A random intercept was also included into the model because the effects of the parameters are likely to vary between countries. A total of 6429 people answered “don’t know” to the questions assessing whether they had discussion donation with their family, were aware of their nation’s legislation, and were willing to donate their organs. These people were excluded from the analysis. There were therefore 22,859 participants in the final analysis. Multiple imputation was not used because this data was not missing at random.

The type of consent used in a country (opt-in vs. opt-out) did not have a significant effect on people’s willingness to donate their organs (Table 4). People were more willing to donate their organs when they were aware than unaware of their nation’s legislation. Similarly, people were more willing to donate their organs when they had discussed donation with their family. The interaction between consent legislation and discussing donation with one’s family was nonsignificant. Importantly, the interaction between consent and awareness of legislation was significant. Simple slopes analysis revealed that when people were not aware of the legislative system, consent did not have a significant effect on donation (b=0.10; P=0.634; odds ratio=1.11). By contrast, when people were aware of the legislative system, consent increased the likelihood of participants donating their own organs (b=0.45; P=0.051; odds ratio=1.56). These results reflect the fact that opt-out consent legislation only increased people’s willingness to donate their organs when they were aware of their nation’s legislative system.

TABLE 4: Willingness to donate one’s own organs

Covariates

The results for the covariates are also presented in Table 4. GDP positively predicted people’s willingness to donate their organs. Legal system and Catholicism were nonsignificant predictors. Males and females did not differ in their willingness to donate their organs. Age negatively predicted donation. People who left education before the age of 17 years were less likely to donate their organs than (a) people who left education between the ages of 17 and 19 years, (b) people who left education after the age of 19 years, and (c) people who were still studying.

DISCUSSION

This study found that opt-out consent legislation only increased people’s willingness to donate their organs when they were aware of their nation’s legislative system. Importantly, this effect was significant after controlling for extraneous factors that also predicted people’s willingness to donate their organs (e.g., education, age, and GDP), thereby demonstrating the robustness of these findings. Moreover, we extend previous research (^{6, 7}) by demonstrating that people must be aware of their nation’s legislative system in order for it to affect their willingness to donate their organs. It should be noted, however, that although deceased donor rates are higher in opt-out than opt-in consent countries (^{6, 10, 11}), opt-out consent countries still have a shortage of donor organs and have significant transplant waiting lists. Indeed, a substantial proportion of people in opt-out countries are reluctant to donate their own or a loved one’s organs (²¹), which may reduce the supply of donor organs. This research suggests that opt-out consent legislation is likely to be most effective in increasing people’s willingness to donate their organs when people are aware of their nation’s legislative system. Opt-out consent nations should therefore increase people’s awareness of their legislative system to increase people’s willingness to donate their organs. The introduction of awareness campaigns may be a simple strategy for increasing people’s willingness to donate their organs, which may, in turn, increase the number of organs donated.

Recent research has highlighted the importance of assessing the factors that are likely to moderate the effect of opt-out legislation on organ donation (⁸). People’s awareness of their nation’s legislation is one such factor. However, there are likely to be other variables that may moderate the effect of opt-out legislation on organ donation. For example, Brazil had to revoke opt-out legislation that it had introduced a year earlier because it had a detrimental effect on donation. This was believed to be due to people believing that medical professionals may take their organs before they were actually dead (²⁵), a concern that is commonly known as “medical mistrust” (^{26, 27}). The effect of opt-out legislation is therefore likely to be moderated by medical mistrust, with this legislation being most successful in populations with low levels of mistrust. It is important to understand the factors that moderate the effectiveness of opt-out consent to ensure that the introduction of such legislation has a positive impact on organ donation and to maximize its effectiveness.

It is important to consider the limitations of this research. First, this research assessed people’s willingness to donate rather than their behavior. Previous research has demonstrated that although people may have the intention to donate, they do not always undertake the actions required to ensure that their organs are available for donation, such as registering as a posthumous organ donor (^{28, 29}). Second, 6429 people were excluded from the analysis because they selected “don’t know” as an answer to one of the organ donation questions from the Eurobarometer. It would be interesting to determine whether such answers reflect genuine uncertainly regarding one’s answer or a reluctance to answer the question. Finally, consent and awareness of legislation were measured rather than manipulated, preventing researchers from inferring causality from these results. Indeed, this is a problem with the vast majority of research investigating the effects of opt-out consent on organ donation rates (^{16, 17}). Further experimental research is therefore urgently needed. Although it may not be practical to experimentally manipulate consent legislation, previous research has demonstrated a causal effect using vignette studies (⁶).

In conclusion, this research found that opt-out consent legislation is likely to increase people’s willingness to donate their organs for transplant purposes but only when people are aware of the legislative system in which their nation operates. This finding suggests that opt-out consent nations may increase people’s willingness to donate their organs by increasing people’s awareness of their legislative system. This research also highlights the importance of understanding the factors that moderate the effect of opt-out consent legislation on organ donation to ensure that such legislation has a positive impact on donation and that its effectiveness is maximized.

MATERIALS AND METHODS

The participant’s age, gender, and level of education was obtained from the Eurobarometer (²⁰). Age (in years) was a continuous variable. Gender was a category variable (male vs. female). Education referred to the age (in years) that the participant left full-time education. This variable was split into four categories: 16 years or below, 17 to 19 years, 20 years and older, or still studying. The Eurobarometer also measured whether people had discussed organ donation with their family, their awareness of their nation’s legislation, and their willingness to donate their own organs. Awareness of national law was assessed using a single item: “The donation and transplantation of human organs is regulated by (NATIONALITY) law. Do you know the regulations in (OUR COUNTRY) for the donation and transplantation of human organs?” People’s willingness to donate their own organs was assessed using a single item: “Would you be willing to donate one of your organs to an organ donation service immediately after your death?” A single item was also used to determine whether the participant had discussed organ donation with their family: “Have you ever discussed human organ donation or transplantation with your family?” Participants answered “yes,” “no,” or “don’t know” to each of these three questions.

Each country’s consent legislation (opt-out vs. opt-in) was obtained from previous research (^{5, 10, 22, 30}). Previous research has made a distinction between opt-out consent countries were a family members’ permission is required (soft opt-out) and is not required (hard opt-out) for donation to occur (²¹). Although this is of interest, such categorization may be problematic because there are numerous countries that have hard opt-out consent laws but unofficially use soft opt-out consent. Because of this subjectivity, we did not make this distinction.

It is also important to control for variables that vary between each country (i.e., GDP, legal system, and Catholicism) to ensure that they are not responsible for the effects of consent legislation on donation. GDP is closely associated with organ donation rates (¹²). It is therefore important to control for GDP to ensure that the hypothesized effects were not dependent on or influenced by this variable. Each country’s GDP (USD per capita) at the time that the survey was undertaken (2009) was obtained from the World Bank (³¹). This was a continuous variable.

Opt-in consent countries are more likely to have common than civil law systems (¹⁰). Because of this association, each country’s legal system was entered into the analysis to ensure that the effects of consent legislation were not in fact due to this extraneous variable. Each country’s legal system was obtained from the Central Intelligence Agency World Factbook (³²). There were three law categories: civil, common, or a mixture of civil and common law.

The Catholic Church strongly endorses organ donation because this act prolongs life. Countries with a high proportion of Catholics are therefore more likely to introduce policies that may increase donation, such as opt-out consent. Indeed, countries with a high proportion of Catholics are more likely to use opt-out than opt-in consent legislation (¹⁰). It is therefore important to control for the proportion of Catholics in a country to ensure that the effects of consent legislation are not due to this extraneous variable. The percentage of self-identified Catholics in each country was obtained from the Central Intelligence Agency World Factbook (³²).