Description and characteristics of studies

We initially identified 377 studies (Figure 1). Subsequent screening by title and abstract led to the exclusion of 121 articles that were irrelevant to the research question. Additionally, we excluded 136 review articles, 7 case reports, 30 protocol/expert-opinion/guideline articles, 9 survey articles among neurologists, 12 non-English articles, 4 articles unavailable as full text, 8 studies on atypical Parkinsonism, 3 trial descriptions and 5 articles related to COVID-19 PC. Finally, 42 articles were included. The included studies comprised 23 qualitative studies, 2 randomized controlled trials (RCTs), 8 cross-sectional studies, 6 survey-based studies, 1 interventional study, 1 cohort study, and 1 case-control study. Studies that used a qualitative design were used to assess the types of narratives (i.e., based on Arthur W. Frank’s illness narrative types – chaos-stories, restitution-stories, and quest-stories) shared by individuals with PD. Of these, 24 investigated ACP (Supplemental Table 1), while 18 focused on PC in PD (Supplemental Table 2).

Figure 1.

Article flowchart showing inclusions and exclusions.

Figure 1 Long description

The flowchart outlines a systematic literature search conducted on February 2nd, 2026, starting with 377 published papers sourced from PubMed (114), Embase (85), Web of Science (80), Cochrane Library (19), CINAHL (49) and PsycINFO (30). The process includes the exclusion of 121 studies for not meeting criteria. Additionally, 214 full-text articles are excluded for various reasons: 136 reviews, 7 case reports, 30 protocol/opinion/guideline articles, 8 atypical Parkinsonian studies, 5 COVID-19 related studies, 12 non-English articles, 9 articles on neurologists′ views, 4 unavailable as full text and 3 trial descriptions. Finally, 42 full-text articles are assessed for eligibility and included in qualitative synthesis.

Knowledge of ACP or PC

Knowledge and awareness of ACP and PC among individuals with PD and their caregivers varied across studies. Specifically, insufficient information or incomplete understanding explained a reduced awareness or lower occurrence of ACP among n= 1929 out of 4154 individuals with PD (46.4%) in 10 out of 24 studies (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011; Boersma et al. Reference Boersma, Jones and Carter2016; Habermann and Shin Reference Habermann and Shin2017; Kluger et al. Reference Kluger, Shattuck and Berk2019; Lum et al. Reference Lum, Jordan and Brungardt2019; Churm et al. Reference Churm, Dickinson and Robinson2022a, Reference Churm, Dickinson and Robinson2022b; Seshadri et al. Reference Seshadri, Dini and Macchi2023; Lennaerts-Kats et al. Reference Lennaerts-Kats, Daeter and Forkink2024; Peabody et al. Reference Peabody, Abou-ezzi and Hernandez2025). Individuals with PD and their caregivers often struggled to identify relevant questions regarding disease progression and future care, and individuals with PD frequently reported insufficient information about prognosis. Caregivers also noted a lack of information provided after diagnosis particularly regarding disease progression and future planning.

Regarding studies into PC, insufficient knowledge explained a lower occurrence of PC for n = 1564 individuals with PD in 13 out of 18 studies (Giles and Miyasaki Reference Giles and Miyasaki2009; Hasson et al. Reference Hasson, Kernohan and McLaughlin2010; Fox et al. Reference Fox, Cashell and Kernohan2017; Klietz et al. Reference Klietz, Tulke and Müschen2018; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020, Reference Lennaerts-Kats, Ebenau and van der Steen2022; Prizer et al. Reference Prizer, Gay and Wilson2020; Chen et al. Reference Chen, Zhang and Lou2023; Kundrick et al. Reference Kundrick, Hogue and Namrow2023; Bock et al. Reference Bock, Macchi and Harrison2024; Seshadri et al. Reference Seshadri, Contento and Sugiura2024a, Reference Seshadri, Dini and Corcoran2024b; Karmur et al. Reference Karmur, Sipai and Mori2025). This lack of knowledge of ACP and PC can occur because medical decisions are made without consulting family caregivers or clinicians (Lum et al. Reference Lum, Jordan and Brungardt2019). Other factors contributing to this limited knowledge included unfamiliarity with ACP terminology, how to utilize advance directives (ADs; Churm et al. Reference Churm, Dickinson and Robinson2022b), inadequate understanding of disease prognosis (Clarke et al. Reference Clarke, Fistein and Holland2018), and insufficient information about disease progression (Kurpershoek et al. Reference Kurpershoek, Hillen and Medendorp2021). Interestingly, a very small subset of individuals with PD (n= 30) who perceived a lack of interest from neurologists in advance planning were uncertain about completing an AD but also about the ACP process (Boersma et al. Reference Boersma, Jones and Carter2016). Regarding PC itself, some individuals with PD (n= 47) received minimal guidance or emotional support from their neurologists to manage their care (Prizer et al. Reference Prizer, Gay and Wilson2020). In another small subset study of n= 10, individuals with PD misunderstood PC as “home help” or “counseling,” or mistakenly believed it was only for those with a cancer diagnosis (Fox et al. Reference Fox, Cashell and Kernohan2017). Some patients expressed a need for additional information about PC, particularly regarding ACP for end-of-life care (Klietz et al. Reference Klietz, Tulke and Müschen2018). Caregivers also noted a deficiency in sufficient information provided following diagnosis (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011), along with delays in recognizing the palliative stage of PD (Fox et al. Reference Fox, Cashell and Kernohan2016). In a study involving patients with late-stage PD (n= 10), participants prioritized present care over advance planning thereby expressing a desire to prolong their stay at home (Read et al. Reference Read, Cable and Löfqvist2019).

Timing of ACP or PC

The timing of ACP is often delayed and uncertain. Misconceptions that ACP or PC is only relevant when caregivers can no longer manage, led to late discussions thereby often delaying ACP until a crisis. In 9 out of 24 studies involving n= 1576 individuals with PD and n= 721 care partners or health care workers, the start of ACP discussions was delayed until the end of the disease trajectory (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011; Boersma et al. Reference Boersma, Jones and Carter2016; Fox et al. Reference Fox, Cashell and Kernohan2016; Lum et al. Reference Lum, Jordan and Brungardt2019; Read et al. Reference Read, Cable and Löfqvist2019; Churm et al. Reference Churm, Dickinson and Robinson2022a, Reference Churm, Dickinson and Robinson2022b; Seshadri et al. Reference Seshadri, Dini and Macchi2023; Peabody et al. Reference Peabody, Abou-ezzi and Hernandez2025). ACP was frequently neglected unless initiated by patients and some patients and caregivers viewed it mainly as completing ADs rather than discussing values and future care. Moreover, in 1 study involving a sample of 1266 individuals with PD, ACP was often disregarded unless initiated by the patient themselves (Seshadri et al. Reference Seshadri, Dini and Macchi2023). Even when individuals with PD do initiate the process, ACP discussions might still be overlooked by neurologists due to feelings of uncertainty (Boersma et al. Reference Boersma, Jones and Carter2016) or hesitation in individuals with PD (Read et al. Reference Read, Cable and Löfqvist2019). Individuals with PD find it challenging to determine the right timing for ACP, viewing it as a future event that is linked to health changes (Churm et al. Reference Churm, Dickinson and Robinson2022a). This could explain why in 3 separate studies involving 240 individuals diagnosed with PD, there was a preference for initiating ACP early on (Tuck et al. Reference Tuck, Brod and Nutt2015; Kluger et al. Reference Kluger, Shattuck and Berk2019; Kurpershoek et al. Reference Kurpershoek, Hillen and Medendorp2021). In the largest study of those 3 studies involving 106 individuals with PD, 37.7% believed that neurologists should initiate ACP discussions early in their illness (Kundrick et al. Reference Kundrick, Hogue and Namrow2023).

In relation to PC, individuals with PD expressed a clear need for early information about disease progression. Many participants wanted future-oriented discussions with neurologists although opinions differed on the exact timing. Specifically 8 out of 18 studies involving n= 236 individuals with PD and n= 145 care partners or health care workers underscore such a delay in timing (Hasson et al. Reference Hasson, Kernohan and McLaughlin2010; Fox et al. Reference Fox, Cashell and Kernohan2017; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020, Reference Lennaerts-Kats, Ebenau and van der Steen2022, Reference Lennaerts-Kats, Daeter and Forkink2024; Prizer et al. Reference Prizer, Gay and Wilson2020; Kundrick et al. Reference Kundrick, Hogue and Namrow2023; Seshadri et al. Reference Seshadri, Dini and Corcoran2024b). Patients perceived that care planning relied on ad hoc rather than proactive approaches, leaving caregivers without a clear understanding of what to expect in the future. However, timely discussions in PC are preferred in 5 separate studies involving 178 individuals with PD and 10 caregivers (Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020; Kundrick et al. Reference Kundrick, Hogue and Namrow2023; Bock et al. Reference Bock, Macchi and Harrison2024; Seshadri et al. Reference Seshadri, Dini and Corcoran2024b; Karmur et al. Reference Karmur, Sipai and Mori2025). This could be facilitated via more advance guidance (Seshadri et al. Reference Seshadri, Dini and Corcoran2024b) or by providing more information about the disease’s progression (Bock et al. Reference Bock, Macchi and Harrison2024). In a smaller study comprising 19 individuals with PD and 12 caregivers, those individuals with PD in early stages of disease tended to avoid thinking about the future, while those in advanced stages facing declining medication effectiveness, were more willing to consider ACP (Fox et al. Reference Fox, Cashell and Kernohan2017). Moreover, caregivers’ perceptions on PC are often hindered by misconceptions, such as viewing it as necessary only when they couldn’t cope (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011). As a result, discussions are often solely about how to construct ADs, limiting discussions on values (Lum et al. Reference Lum, Jordan and Brungardt2019). Moreover, the uncertainty in caregivers about the timing of ACP delays initiation of end-of-life discussions until calamities, despite recognizing the need for early planning (Fox et al. Reference Fox, Cashell and Kernohan2016).

Perception of autonomy support in ACP or PC

When viewing autonomy as the capacity for self-determination, 11.4% of the individuals with PD in this systematic review (n= 472 out of a total of n= 4154) express a preference for initiating ACP or PC discussions themselves (Hudson et al. Reference Hudson, Toye and Kristjanson2006; Kwak et al. Reference Kwak, Wallendal and Fritsch2014; Tuck et al. Reference Tuck, Brod and Nutt2015; Fox et al. Reference Fox, Cashell and Kernohan2017; Clarke et al. Reference Clarke, Fistein and Holland2018; Klietz et al. Reference Klietz, Öcalan and Schneider2019; Churm et al. Reference Churm, Dickinson and Robinson2022b). This was particularly seen in a survey study involving 82 individuals with PD, for whom a significant motivation for creating ADs was to assert autonomy and responsibility for end-of-life care (Klietz et al. Reference Klietz, Öcalan and Schneider2019). In contrast, most individuals with PD (n= 2258 out of a total of n= 4154 in 23 out of 42 studies) suggest they require more autonomy support to start discussions about ACP or PC (Hasson et al. Reference Hasson, Kernohan and McLaughlin2010; McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011; Boersma et al. Reference Boersma, Jones and Carter2016, Reference Boersma, Jones and Coughlan2017; Fox et al. Reference Fox, Cashell and Kernohan2016; Habermann and Shin Reference Habermann and Shin2017; Klietz et al. Reference Klietz, Tulke and Müschen2018; Lum et al. Reference Lum, Jordan and Brungardt2019; Read et al. Reference Read, Cable and Löfqvist2019; Jordan et al. Reference Jordan, Kluger and Ayele2020; Kluger et al. Reference Kluger, Miyasaki and Katz2020; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020, Reference Lennaerts-Kats, Ebenau and van der Steen2022, Reference Lennaerts-Kats, Daeter and Forkink2024; Prizer et al. Reference Prizer, Gay and Wilson2020; Kurpershoek et al. Reference Kurpershoek, Hillen and Medendorp2021; Nicholas et al. Reference Nicholas, Nicholas and Hannides2021; Churm et al. Reference Churm, Dickinson and Robinson2022a; Chen et al. Reference Chen, Zhang and Lou2023; Kundrick et al. Reference Kundrick, Hogue and Namrow2023; Seshadri et al. Reference Seshadri, Dini and Macchi2023, Reference Seshadri, Dini and Corcoran2024b; Bock et al. Reference Bock, Macchi and Harrison2024). Physicians can facilitate patient autonomy through actions such as providing disease progression details and participating in decision-making to help patients achieve their health objectives and increase their control over managing their condition (Arora et al. Reference Arora, Weaver and Clayman2009). When ACP is conducted by general practitioners (GPs) or in collaboration with GPs and the patient’s family, PD care showed a significant reduction in hospital deaths (Nicholas et al. Reference Nicholas, Nicholas and Hannides2021). However, a small subset of individuals with PD (n= 145 out of 4154) often face inadequate support for autonomy, potentially due to neurologists’ lack of interest in ACP (1 study involving n= 30 individuals with PD) (Boersma et al. Reference Boersma, Jones and Carter2016), their primary focus on motor symptoms (Bock et al. Reference Bock, Macchi and Harrison2024) and conflicting advice regarding the importance of ACP (Lum et al. Reference Lum, Jordan and Brungardt2019; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020, Reference Lennaerts-Kats, Ebenau and van der Steen2022; Seshadri et al. Reference Seshadri, Dini and Corcoran2024b). Furthermore, 50 individuals with PD experience delays in neurologist appointments and their insufficient coordination among healthcare providers increases the emotional, social and financial burden of disease (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011; Prizer et al. Reference Prizer, Gay and Wilson2020). This was also observed in studies concerning PC where a smaller study revealed that individuals with PD specifically expressed a need for attentive listening from their physician and a wish for more extensive discussions on end-of-life issues (Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and van der Steen2022). In a Chinese study, caregivers consistently stressed the significance of healthcare professionals acknowledging the dependency of individuals in advanced stages of PD on PC (Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020). When neurologists appeared to overlook this aspect, general practitioners frequently stepped in to offer assistance through home visits (Hasson et al. Reference Hasson, Kernohan and McLaughlin2010) or via hospital-based, multidisciplinary clinics (Giles and Miyasaki Reference Giles and Miyasaki2009).

Caregivers’ involvement in surrogate decision-making concerning ACP or PC

In 6 out of 37 studies involving n= 674 individuals with PD, caregivers enhanced care (Tuck et al. Reference Tuck, Brod and Nutt2015) and care planning (including increased or earlier ACP or the development of ADs with family cosignatures) (Churm et al. Reference Churm, Dickinson and Robinson2022a, Reference Churm, Dickinson and Robinson2022b; Fox et al. Reference Fox, Gannon and Cashell2015; Klietz et al. Reference Klietz, Öcalan and Schneider2019; Nicholas et al. Reference Nicholas, Nicholas and Hannides2021). In 2 studies, caregivers and individuals with PD (n= 40) collaborated in making difficult decisions (Read et al. Reference Read, Cable and Löfqvist2019; Jordan et al. Reference Jordan, Kluger and Ayele2020). In one of those studies in which several individuals with PD completed an AD, they excluded their physician from the ACP process indicating a preference for management exclusively by the family (Boersma et al. Reference Boersma, Jones and Carter2016). Several caregivers (n= 256 out of 2191) also frequently feel responsible for making medical decisions (Kwak et al. Reference Kwak, Wallendal and Fritsch2014; Churm et al. Reference Churm, Dickinson and Robinson2022a) coordinating timely discussions about prognosis and future symptoms (Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and van der Steen2022) or assuming the role of care coordinator (Bock et al. Reference Bock, Macchi and Harrison2024). However, they often encounter challenges in discussing advanced disease stages with neurologists (Habermann and Shin Reference Habermann and Shin2017), often due to emotional distress (Seshadri et al. Reference Seshadri, Contento and Sugiura2024a), limited awareness of the patient’s preferences (Fox et al. Reference Fox, Cashell and Kernohan2017; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020) or the lack of knowledge of PD course and the possibility of ACP (Habermann and Shin Reference Habermann and Shin2017) or PC (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011). With regard to care planning, barriers within relationships can hinder ACP (Lum et al. Reference Lum, Jordan and Brungardt2019), while the presence of family is reason enough to disregard ACP (Churm et al. Reference Churm, Dickinson and Robinson2022b). Still, in a significant study involving 267 individuals with PD, most (56.6%) indicated a preference for early involvement of their family in the management of the progression of illness (Tuck et al. Reference Tuck, Brod and Nutt2015). Another study involving 82 individuals with PD demonstrated that such early involvement could result in ADs with either a spouse or a family physician co-signing (Klietz et al. Reference Klietz, Öcalan and Schneider2019).

Types of narratives shared by individuals with PD in studies on ACP or PC

Arthur W. Frank identifies 3 types of illness narratives (Frank Reference Frank2013). Restitution stories show illness as temporary, focusing on getting better and returning to normal life. Chaos stories describe the confusion and disorder that illness brings, showing how out of control it can feel. Quest stories are accepting illness and trying to find meaning or personal growth through the experience. Most of the identified narrative types narrated by individuals with PD and caregivers were chaos narratives. They appeared in 8 studies on ACP (McLaughlin et al. Reference McLaughlin, Hasson and Kernohan2011; Boersma et al. Reference Boersma, Jones and Carter2016, Reference Boersma, Jones and Coughlan2017; Klietz et al. Reference Klietz, Öcalan and Schneider2019; Kluger et al. Reference Kluger, Shattuck and Berk2019; Jordan et al. Reference Jordan, Kluger and Ayele2020; Churm et al. Reference Churm, Dickinson and Robinson2022b; Seshadri et al. Reference Seshadri, Dini and Macchi2023) involving n= 1572 individuals with PD and 9 studies on PC involving n= 140 individuals with PD (Hudson et al. Reference Hudson, Toye and Kristjanson2006; Giles and Miyasaki Reference Giles and Miyasaki2009; Hasson et al. Reference Hasson, Kernohan and McLaughlin2010; Fox et al. Reference Fox, Cashell and Kernohan2017; Badger et al. Reference Badger, Frizelle and Adams2018; Klietz et al. Reference Klietz, Tulke and Müschen2018; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and Steppe2020; Seshadri et al. Reference Seshadri, Contento and Sugiura2024a, Reference Seshadri, Dini and Corcoran2024b). Quest narratives were found in 5 studies on ACP involving n= 330 individuals with PD (Tuck et al. Reference Tuck, Brod and Nutt2015; Clarke et al. Reference Clarke, Fistein and Holland2018; Lum et al. Reference Lum, Jordan and Brungardt2019; Read et al. Reference Read, Cable and Löfqvist2019; Kurpershoek et al. Reference Kurpershoek, Hillen and Medendorp2021) and 4 studies into PC involving n= 83 individuals with PD (Prizer et al. Reference Prizer, Gay and Wilson2020; Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and van der Steen2022; Chen et al. Reference Chen, Zhang and Lou2023; Bock et al. Reference Bock, Macchi and Harrison2024). Quest narratives were identified in qualitative studies among individuals with PD who aimed to initiate ACP at the earliest opportunity (Tuck et al. Reference Tuck, Brod and Nutt2015; Kurpershoek et al. Reference Kurpershoek, Hillen and Medendorp2021) to uphold their identity despite PD (Read et al. Reference Read, Cable and Löfqvist2019), or sought to independently navigate resources to address nonphysical needs (Prizer et al. Reference Prizer, Gay and Wilson2020). In studies assessing PC, quest narratives became apparent when it was observed that individuals with PD had limited comprehension of PC but showed an interest in it (Chen et al. Reference Chen, Zhang and Lou2023), felt obliged to communicate healthcare information to their providers (Prizer et al. Reference Prizer, Gay and Wilson2020) or sought honest discussions with healthcare professionals about their health (Lennaerts-Kats et al. Reference Lennaerts-Kats, Ebenau and van der Steen2022).

Effectiveness of intervention studies to improve ACP or PC

Interventions evaluating counseling to support the ACP process show that patients and caregivers report positive experiences leading to a better understanding of the current health situation, future care needs and end-of-life decisions. Specifically in the study by Lennaerts-Kats et al., patients and caregivers describe the counseling as supportive and helpful in gaining a clearer understanding of their current health status and future care needs including end-of-life decisions (Lennaerts-Kats et al. Reference Lennaerts-Kats, Daeter and Forkink2024). Kluger and co-authors have investigated whether an outpatient PC intervention enhances outcomes for individuals with PD and caregivers compared to standard care (Kluger et al. Reference Kluger, Miyasaki and Katz2020). In the PC intervention group, this led to better quality of life (QOL) and individuals with PD were more likely to have completed ADs (67.0%, n= 59 of 88 versus 30.3%, n= 23 of 76 in the control group) (Kluger et al. Reference Kluger, Miyasaki and Katz2020). Other significant improvements following the PC intervention were a reduced motor symptom severity, lower non-motor symptom burden, decreased caregiver anxiety and alleviated caregiver burden at 12-months (Kluger et al. Reference Kluger, Miyasaki and Katz2020). In a secondary analysis of the same trial, the authors used longitudinal regression models to study changes in QOL of individuals with PD and care partners, while Spearman correlations were used to evaluate the correlates of score changes in outcomes (Kluger et al. Reference Kluger, Miyasaki and Katz2020). This identified that individuals with PD reported (among others) improvements in anxiety, well-being, stiffness and total symptom burden, all of which correlated significantly with enhanced QOL (Bock et al. Reference Bock, Katz and Sillau2022). Moreover, reductions in patient anxiety, depression, and grief throughout the study period were also significantly associated with improvements in patient QOL (Bock et al. Reference Bock, Katz and Sillau2022).