Background

Euthanasia is defined as the intentional killing of a competent person upon her voluntary request, usually performed by a physician [43]. In contrast, AS is the intentional helping of a competent person to commit suicide by providing lethal drugs for self-administration [43]. At the time of writing, euthanasia and/or AS are legal in four European countries (the Netherlands, Belgium, Luxembourg, Switzerland), in eight US states, in Canada, in Victoria (Australia) and in Colombia, while other countries such as France, Germany, Italy, and Spain are currently discussing the potential legalization of euthanasia and/or AS [44]. Most countries in which euthanasia and/or AS are legal have strongly regulated their practice and established certain safeguards. These include requiring two concurring medical opinions for any euthanasia or AS request, having a delay between the granting and carrying out of any such request, requiring psychiatric assessments of patients, and/or making restrictions on patient’s age, diagnosis or symptom state [26, 29].

In Switzerland, the practice of AS remains relatively unregulated to date, with few formal restrictions or safeguards in place to restrict the use of AS [45]. While euthanasia remains illegal (Art. 114 of the Swiss Criminal Code), the practice of AS is mainly regulated through article 115 of the Swiss Penal Code. Article 115 stipulates that assisting a person in committing suicide is not punished as long as this practice is (a) not performed for selfish reasons (e.g., obtaining an inheritance or making money) and (b) the person seeking for AS has decisional capacity. Thus, in Switzerland, the practice of AS does not require the presence of a physician. However, according to the Swiss Law of Pharmaceutical Products [46], the lethal drug (sodium pentobarbital) usually used for causing death must be provided by a physician who ought to examine the wish to die and the decisional capacity of the person seeking AS. In addition to being subject to these two laws regulating the practice of AS in Switzerland, the large majority of physicians in Switzerland (91%) are affiliated with the Swiss Medical Association (FMH), and thus bound to observe its code of ethics. The code of ethics of the FMH includes the medico-ethical guidelines of the Swiss Academy of Medical Sciences (SAMS), in particular those on the management of dying and death. The latter guidelines stipulate that AS is not considered as part of a doctor’s duties. However, physicians who wish to engage in this practice are legally authorized to do so under specific requirements mainly related to the patient’s mental capacity, persistent and not pressured wish to die, and the intractability of her/his disease or impairment [47]. The former version of the SAMS guidelines also stipulated that the patients must be “close to death” in order to receive AS. In the new SAMS guidelines of 2018, this has been replaced by the notion of “intolerable suffering”. This notion has been rejected as “too vague” by the FMH, which for the first time has refused to adopt the SAMS guidelines in its code of ethics, thus creating an “ethical uncertainty” of sorts for Swiss physicians on this matter.

Since the 1980s, not-for-profit right-to-die organisations, which advocate the right to self-determination in death, have been assisting persons with suicide under the regulation of article 115. Anyone can become a fee-paying member of a right-to-die organisation at any time, even without any immediate or future intention to request AS. Membership in such organisations grants access to their services provided that the person seeking AS meets the internal criteria of the respective right-to-die organisation [46]. Almost all AS in Switzerland are organised by one of these right-to-die organisations [48]. In 2016, AS represented 1.4% of all deaths in Switzerland and 86% of these deaths occurred in adults aged 65 years or older [49].

Measures

Missing values.

Across the 66 variables used in our analysis, proportions of missing values ranged between 0% and 17%, with 66% of observations representing complete cases with no missing item (Table 1 details the distribution of missing values). Since the results of Little tests [58] rejected the hypothesis that our missing values were missing completely at random (MCAR), we conducted our analyses on imputed data. Specifically, multiple imputations by chained equations were used to handle the presence of missing values in our data. 200 imputed datasets were computed in order to calculate asymptotically correct margins. The imputation equations were based on all sociodemographic and family characteristics, as well as on linguistic region variables included in our study. We run logistic regressions using observations with no missing data on the respective dependent variable, which results in small variability in the outcome-specific sample sizes [59]. Parameter estimates and standard errors of logistic regression models based on imputed data sets using Rubin’s formulas [60] were compared with the results of the same regression models using complete cases (available in S2 Appendix). Resulting estimates of the different logistic regression models based on the imputed data were comparable to the corresponding estimates based on a complete case analysis, but statistical precision was higher when using imputed data.

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Table 1. Main characteristics of the analytical sample, adults aged 55+ in Switzerland, SHARE 2015.

https://doi.org/10.1371/journal.pone.0232109.t001

End-of-life preferences may shape attitudes towards assisted suicide

In our study, preferences for controlling one’s end of life, e.g., attaching importance to planning the events following one’s death, to choosing where to die, to preparing one’s family for one’s death (full details is provided in S1 Appendix), were positively associated with support for the legality of AS and with potential use of AS. Similar positive associations with AS-related attitudes and behaviours were also found among respondents who considered it important to be able to maintain essential capabilities at the end of life, such as personal hygiene, self-feeding, living without pain and retaining full mental awareness. Our results are consistent with previous studies that found higher rates of acceptance of euthanasia and/or AS in people that place higher value on self-determination and physical and mental independence at the end of life, as well as in people stating stronger preferences for dying with dignity and without suffering [27, 34]. In addition, our data show that higher levels of importance attached to feeling socially and spiritually connected at the end of life, such as being able to talk about one’s fears, to be spiritually or religiously accompanied or to spend time with family and friends, were negatively correlated with support for the legality of AS and potential use of AS.

Rodríguez-Prat et al. provide a useful explanatory model for interpreting the opposing associations of different EOL preferences with support for AS [61], identifying two types of dignity related to EOL situations. Dignity based on social and spiritual values such as having a positive impact on family ties or having spiritual or religious beliefs is called “intrinsic dignity”, and contrasts with dignity based on values such as autonomy, control and quality of life, collectively referred to here as "extrinsic dignity". When confronted with serious illness and its consequences of mental and physical decline, individuals with intrinsic dignity may be more likely to maintain a positive view of themselves than those with extrinsic dignity based on autonomy and control. We can consider that respondents who placed high importance on feeling socially and spiritually connected at the end of life are more likely to have intrinsic dignity, while those who placed high importance on maintaining essential capabilities at the end of life and having control over one’s end of life are more likely to have extrinsic dignity. Since it allows control over EOL timing and escape from some physical deterioration, AS is an EOL option that may better meet the EOL-related concerns of people with extrinsic dignity.

Fear of being a burden is not a motivation for favourable attitudes to assisted suicide

One of the arguments for the slippery slope is the fear that people will be directly or indirectly pushed to use euthanasia or AS for reasons such as not wanting to be a burden on others [26]. As the social and fiscal challenges of population aging have become a major societal concern, older adults may increasingly feel guilty of potentially becoming a burden for their relatives and society and thus may request AS for social and economic reasons. Two studies reported a positive association between approval of euthanasia in terminally-ill patients requesting it on the one hand and individual concerns of becoming a burden on the family on the other [34, 62]. In 2018, the Swiss population considered the financial sustainability of social security pensions (old-age and surviving dependents insurance, AHV) as well as of health and health insurance systems as the two most worrying current social issues [63] with population aging being a main driver of these challenges of financial sustainability. In this context, one may have expected that respondents who are concerned about being a burden should be more likely to support and consider AS for themselves, perhaps seeing it as a “duty to die” [64]. However, our data show that the self-rated importance of not being a burden does not appear to be the main motivation for supporting AS. Several factors may explain the negative associations between importance of not becoming a burden and AS-related attitudes. First, people who attach high importance to not being a burden may not support the current AS law if they fear to be pressured into AS. Second, many different situations that can be considered as burdening at the end of life and different notions of burden may impact attitudes toward AS differently. For example, individuals may not want to cause a psychological burden to their loved ones by choosing to die by AS, as witnessing an AS by a loved one can have a negative effect on the mental health of remaining family members and friends [23].

Preference for control over end of life and fear of severe decline are positively associated with membership in a right-to-die organisation

In our study, older adults with a higher preference for controlling their end of life and for maintaining essential capabilities at their end of life were more likely to report that they plan to become or already were a member of a right-to-die organisation. Similarly, a study showed that the desire to keep control over the end of life and the time of death, as well as the fear of intolerable suffering and health decline were the main motivations for registering in a right-to-die organization in Switzerland [65]. Furthermore, individuals who died by AS shared similar attitudes in Switzerland and in Oregon. Specifically, these individuals often wished to control circumstances of and place of death, feared dependency [31, 66], and were worried about loss of dignity and future loss of quality of life and of self-care ability [31]. These similarities suggest that AS appeals especially to individuals who share the same concerns regarding their end of life.

The general public needs to be better informed about different end-of-life options

Fears of losing control, mental and physical decline, and pain at the end of life are major concerns for most people [67]. Our study showed that people who are particularly worried about these EOL issues were more likely to have favourable attitudes and behaviours towards AS. This suggests that some people regard AS as a tool for improved self-determination, i.e., as a potential solution to end unbearable suffering and to ensure better control over their end of life [32]. Alternative solutions, such as advance directives and palliative care, may also be able to address these worries; both are available in Switzerland. However, knowledge about the existence of these options for EOL planning and care is lacking in some parts of Switzerland [68, 69]. Improved knowledge about the full range of available EOL options may potentially reduce the number of AS in Switzerland. Even high quality palliative care, however, cannot prevent some consequences of illness, such as loss of control and of autonomy [27]; thus AS may still remain a preference for some patients [29, 66, 70].

Support for assisted suicide is positively associated with trust in institutions with regard to end-of-life issues

Previous studies have found that in countries with a high level of acceptance of euthanasia, such as in Scandinavian countries, the level of trust in the state was also high [26]. The Swiss population also shows high levels of trust in its government, but also in public institutions such as the Federal Tribunal, which is the highest court in Switzerland, and the police [63]. Our study documented similarly high levels of trust in social and public institutions with respect to EOL issues. Furthermore, Köneke showed a positive association between high levels of trust in others and euthanasia acceptance in European countries [26]. Our results corroborate this trend by showing that trust in the social and public institutions directly or indirectly involved in the good use of AS is associated with increased support for AS and potential use of AS. In particular, we found that trust in relatives was strongly positively associated with supporting the legality of AS and being able to consider AS. As families often carry out or help in performing administrative work related to AS requests in Switzerland [23, 71], trust in relatives appears to be a prerequisite for supporting AS and considering it for oneself. Similarly, we observed that trust in healthcare providers and the healthcare system was positively associated, but not statistically significant, with support for AS and potential use of AS. A number of authors assumed there would be a positive association between trust in physicians or healthcare system and euthanasia acceptance [26, 28, 72], but observed in their study an absence of [73] and even negative [26, 36, 40] associations between the two variables.

One might have expected that mistrust in healthcare services and providers in Switzerland would lead to increased support for AS. Indeed, since it is not in the hands of the medical profession, AS could be seen as a way to escape from distrusted healthcare services and providers. However, our study showed that the high support for AS practice is not the result of a deficient or distrusted healthcare system. Moreover, the positive association between trust in the Swiss legal system with regard to EOL issues and AS-related attitudes (although not all statistically significant) may appear in respondents’ beliefs that the judiciary can act as a gatekeeper against potential abuses of AS. The Swiss judiciary ought to ensure that no abuse occurs in the use of AS. When AS misuse is suspected, an investigation is opened, as in the Minelli model lawsuit [74]. Thus, our study seem to suggest that trust in social and public institutions directly or indirectly involved in the good use of AS may be a relevant determinant of AS-related attitudes.

We found negative associations between AS-related attitudes and trust in healthcare insurance companies. This association may indicate that higher levels of trust in health insurance companies may result in a lower need for concern e.g. about accessibility or potential financial consequences of intensive EOL medicine in the absence of AS, though further research is needed to better understand this pattern. At the same time, our results showed a negative association of trust in religious authorities, which can be readily explained by the strong moral disapproval for the active ending of life, based on the sanctity of life principle, of most institutionalised religions (e.g. Catholicism, Buddhism, Islam, Judaism) [75]. In fact, most studies exploring the relationship between religious dimensions on the one hand and euthanasia, physician-assisted AS or AS in general on the other reported similar negative associations between religious beliefs and voluntary active ending of life [26–28, 30, 36–38, 40, 73, 76–78].

Finally, trust in social and public institutions was weakly or not associated with potential and current membership in a right-to-die organization, with the exception of trust in religious authorities, which showed a strong negative association. Hence, while trust in institutions was associated with attitudes toward AS, these did not (yet) seem to translate into concrete action, such as actual or planned membership in a right-to-die organization. Rather, potential and current membership in a right-to-die organization appears to be more closely related to individual preferences than trust in institutions.

Our study has several limitations. First, our results rely partially on the use of imputed data to replace missing values, although a complete case analysis resulted in largely similar findings and the imputation procedure carefully followed standard practice as described in the method section. Second, some of our outcome measures refer to intentions and hypothetical future scenarios such as potentially considering AS for oneself under certain circumstances and planning to become a member of a right-to die organisation in the future. Such statements need to be treated with caution in view of their largely unknown validity for predicting future behaviours. While we know that stated intentions do often, but not always, predict behaviours [79], potential discrepancies between intentions and behaviours may be more frequent in assessments of potential future behaviours in hypothetical situations that are not completely specified (“certain circumstances”). Nonetheless, some research indicates that intentions regarding the EOL behaviours may be quite reliable. First, individuals who potentially consider AS for themselves [34], and those who registered in a right-to-die organisation [80], or died of AS [31, 66, 81] all shared common attitudes such as a wish to control their end of life and a fear of infirmity and decline at the end of life. Second, individuals’ attitudes toward death and dying in the general population appear to be relatively stable over time [36]. Third, most people who died by AS appear to have made their decisions to use AS before their illness [66].