Disparities in Access to Deep Brain Stimulation for Parkinson’s Disease and Proposed Interventions: A Literature Review Open Access

Racial, socioeconomic, and gender disparities, leading to delays in diagnosis, treatment, and worsened overall survival have been demonstrated in patients with Parkinson’s disease (PD) [1]. DBS is an effective treatment option for advanced PD and is associated with improvement in motor symptom control and quality of life [2, 3]. Given that DBS candidacy is evaluated via a multidisciplinary team of neurologists, neuropsychologists, and neurosurgeons, there are several steps along the DBS approval process that may contribute to disparities in access and patient outcomes [4, 5]. These steps are also areas to target with interventions to reduce disparities. Previous studies have shown differences in patient access to DBS based on race, socioeconomic status, and gender [6‒17].

Women are underrepresented in clinical trials [18] and are less likely than men to undergo to DBS. One study found that only 30% of PD patients treated with DBS are women [6], while women represent approximately 42% of patients with PD [19]. In the Medicare population, women with PD are 21% less likely to undergo DBS than men [13].

Racial and ethnic minority patients are also less likely to undergo DBS, even when controlling for disease severity and demographic factors. For example, various studies conducted in the USA found that black PD patients were less likely to receive DBS than white patients, after controlling for disease severity and healthcare access [13, 16]. Socioeconomic status has also been shown to impact access to DBS, with studies showing that patients from wealthier communities and with private insurance are more likely to receive DBS [6, 11‒13].

Much current research focuses on identifying and, to a lesser extent, understanding the underlying causes that propagate DBS disparities; however, few studies discuss potential interventions aimed at mitigating these disparities [20]. Prior studies have argued that unconscious biases among healthcare providers, lack of patient awareness and understanding of treatment options, and limited resources may all contribute to inequities in access [7, 8, 21]. This review will examine disparities in access to DBS across race, gender, and socioeconomic status as well as provide an overview of possible provider, patient, community, and policy/organizational-level evidence-based interventions.

A literature review was performed to investigate disparities in access to DBS surgery. The search terms included (“deep brain stimulation” OR “DBS”) AND (“disparities” OR “inequality” OR “healthcare disparities” OR “racial disparities” OR “ethnic disparities” OR “socioeconomic disparities” OR “minority populations” OR “gender” OR “gender disparities”). Original studies that investigated any type of disparity relating to access to DBS from 1990 to present day were considered. Letters to the editor, commentaries, and articles of editorials were excluded from review. The search process included screening the title, abstract, and full-text article. Papers that did not specifically discuss disparities in access to DBS were excluded in the final qualitative analysis. Papers that discussed disparities in outcome were also excluded in the final analysis. Studies from all countries were considered, but an English version of the article was required for inclusion in the analysis. A flow diagram is provided in Figure 1.

Of the 1,162 initially screened studies, 13 met inclusion criteria (Fig. 1; Table 1) [6‒17, 22], with publication years spanning 2014–2023. Studies originated from 5 different countries, with 8 (66.7%) from the USA. All studies performed a retrospective cohort analysis. The findings from these studies are synthesized and summarized below.

There has been increased recognition of gender disparities in access to services across medical fields [23‒25], and such disparities are also seen in neurosurgery. Gender disparities are also present in DBS: among Medicare beneficiaries, women with PD are 21% less likely than men to receive DBS, even after adjusting for age, race, socioeconomic status, disease duration, and comorbidities [13]. Factors at multiple points in the DBS evaluation process may contribute to this disparity; we separately consider both disparities in DBS referrals and in DBS utilization after referral [8].

Women are overall less likely to be referred for a DBS candidacy evaluation and have been found to experience a delay both from symptom onset to diagnosis and from diagnosis to referral [26]. One study found that of the PD patients seen in an American neurologic clinic population, a smaller proportion of total female compared to male patients with PD were referred for DBS consideration [6]. Once referred, male and female patients were equally likely to be offered surgery [6]. Similarly, a retrospective analysis at a German university hospital found that women were underrepresented in the population referred for DBS but had a higher probability of approval for DBS after multidisciplinary evaluation (relative risk 1.17) [8]. The authors noted several nonclinical factors that may contribute to the observed gender disparities, including referral biases to specialty care [27, 28], greater fear of surgery [29], or socioeconomic status [28]. One study found that women with PD were 22% less likely to see a neurologist compared to men [30]. Given that most referrals to DBS come from neurologists [31], lower likelihood of seeing a neurologist may contribute to a smaller number of women being referred for surgical consideration.

Notably, some studies have suggested that women may have slower PD symptom progression [32, 33], which could affect identification of women as candidates for DBS. However, women are still underrepresented in DBS surgeries for essential tremor, a disease in which gender-specific symptom differences have not been found [17]. This suggests that differences in symptom progression are not the major factor contributing to gender-related DBS disparities. Additionally, women continue to be underrepresented in PD clinical trials [18], limiting our understanding of PD manifestations and treatment in this population – another manifestation of this disparity.

In addition to disparities impacting referral for DBS surgery, there are gender disparities impacting DBS utilization after referral. Several studies have found that in patients referred for and offered DBS surgery, women are more likely than men to decline surgery [6, 8]. Previous studies have shown that women tend to be more concerned about possible complications of a surgery [6, 34]. One study reported gender differences in the reasons that patients referred for DBS ultimately did not undergo surgery, with women being more likely not to undergo surgery due to personal preference [6]. Women may also be more likely to have caregiving responsibilities or other social or economic contributing factors which may impact their decision to undergo DBS.

Racial disparities in access to neurosurgical procedures are a pervasive problem that has been increasingly recognized [35, 36]. In the USA, black PD patients are 5–8 times less likely to undergo DBS than white patients [11, 13]. Black race predicts decreased DBS use even when adjusting for comorbidities [8]. Asian patients also have lower odds ratios of having DBS compared to white patients (adjusted odds ratio of 0.55) [13]. Even when receiving care at urban teaching hospitals with a high density of neurologists and neurosurgeons, black patients with PD undergo disproportionately fewer DBS procedures [8]. This disparity has persisted over time: Cramer et al. [16] examined DBS use before and after 2010 and found that while the total number of DBS surgeries increased, racial disparities remained unchanged.

One study found that there was no difference in DBS use between white and Hispanic Medicare beneficiaries after adjusting for confounders [13]. On the other hand, Hispanic patients with PD were found in a separate study to be less likely to undergo DBS when controlling for patient and hospital characteristics [37]. Given that Hispanic patients are also underrepresented in other neurosurgical procedures such as spine surgery [38], this is an area important for future study.

A number of structural, social, and economic factors impact access to care, which may contribute to racial disparities in DBS access. Previous studies have found racial disparities in access to PD management, which inherently limits evaluation of patients for DBS. Minority populations are less likely to have access to both general and specialized movement disorder neurologists [39, 40]. One study examined all PD-related admissions in Hawaii and found that Native Hawaiian and Pacific Islander (NHPI) and black patients were underrepresented with odds ratios of 0.64 and 0.17, respectively [7], suggesting racial disparities in access to PD care are not limited to DBS. The study notes that NHPI individuals have higher rates of poverty and lack of health insurance which may impact their ability to access PD care [7].

In addition to racial disparities in PD medical management, there are disparities in referral for surgical consideration. Skelton et al. [12] reported that the ratio of black to white medically managed PD patients was 0.38, while that of surgically managed patients was 0.07, with disparities in medical management accounting for only 14% of the overall surgical disparity, suggesting that events between medical management and surgery also contribute to disparities in access [12]. In this study, far fewer black patients were referred for DBS consideration than would be expected based on regional demographics, and once referred, there was no racial difference in the proportion of patients who proceeded to surgery, suggesting that disparities in DBS referrals may be a major contributor to ultimate disparities in DBS utilization [12]. This pattern suggests potential provider bias, as previous studies have provided evidence against comorbidities [11, 16, 38] or initial disease presentation [16] exacerbating referral disparities. In addition, prior studies have presented evidence to suggest black patients experience discrimination to a greater extent than do other minority populations [41‒43]. These findings emphasize the need to address disparities in access to DBS by not only addressing access to general PD care but also by increasing referrals for surgical evaluation, especially among underserved populations.

Other factors including disease, cultural, and social factors may impact racial disparities in DBS use. Some minority populations may have differences in PD progression [44, 45]; black patients with PD have been reported to have higher rates of postural instability on initial evaluation, which could impact the way in which their DBS candidacy is judged [41]. However, a more recent study showed evidence to support that the extent of disease severity on initial presentation does not account for the extent of racial disparity [13]. Indeed, disparities in access to DBS have also been observed outside of PD, such as ET and dystonia [17, 37]. Cultural differences may also impact the way in which patients interpret their symptoms [42] which could ultimately impact patients’ likelihood of presenting for evaluation and treatment. Patient-specific factors, such as underreporting of motor impairment and mistrust of the medical system due to longstanding disparities in care, may contribute to the racial disparity in DBS use [43, 46‒48]. Delay in diagnosis and treatment in minority populations is a broad issue stemming from a variety of structural factors including lack of access to healthcare and disparities in healthcare quality and may impact likelihood of DBS referral [49].

Socioeconomic status also impacts access to DBS. Patients who live in neighborhoods with the highest median income, educational achievement, and housing values are more likely to receive DBS [13, 16]. Similarly, Sarica et al. [17] found that increasing median household income within a given zip code was a positive predictor for DBS use in PD patients. Insurance status is a significant contributor to socioeconomic disparities in DBS access. Patients with private insurance have better access to primary care, which may impact their likelihood of referral to specialty treatment and increase their access to advanced treatment options such as DBS [50, 51]. Several studies have found that patients with private insurance are more likely to undergo DBS, while patients with Medicaid are less likely to undergo DBS [11, 12]. Practitioner avoidance of increased administrative burdens and low monetary reimbursement from government-funded insurance may contribute to decreased DBS use among those relying on Medicaid insurance [52]. Overall, these studies suggest that there are socioeconomic disparities in access and response to DBS therapy, highlighting the need to examine and address the potential underlying causes.

Socioeconomic and racial disparities in access to DBS may interact. Neighborhood and settings of care are linked to socioeconomic status and race, which can ultimately influence access to DBS care. One study found that practices with a large proportion of racial minority patients have fewer patients who ultimately receive DBS [13], and this effect was seen regardless of the race of the individual patients, suggesting that the environment of care may contribute to disparities in access. Similarly, individuals living in neighborhoods with higher concentrations of recent immigrants and visible minorities were found to be less likely to receive DBS surgery [10]. Watanabe et al. [7] reported that Native Hawaiian/Pacific Islander patients who underwent DBS surgery were on average in higher income brackets than Asian and white DBS patients. Chan et al. [11] found that the impact of having Medicaid on likelihood of receiving DBS is modulated by race. White patients using Medicaid are significantly more likely to receive DBS than black patients using either private insurance or Medicare, and black patients with Medicaid are the least likely to receive DBS of any other group combination of race/ethnicity and insurance status [11]. Combined, these findings suggest that socioeconomic status and racial disparities interact in affecting patient access to care.

In 2003, the Institute of Medicine (IOM) released a report to assess the extent and various causes of disparities in healthcare as well as suggest interventions to address these disparities [53]. Nonetheless, the vast majority of research on disparities within neurosurgery is still focused on the identification of disparities associated with treatment of neurosurgical diseases. A 2023 review investigating the current state of racial disparities literature within neurosurgical patients found that only 15.1% and 1.3% of the literature were devoted to understanding the root causes and proposing solutions, respectively, highlighting the importance of continued research [54]. We therefore propose provider, patient, community, and policy and organizational interventions aimed at addressing disparities in access to DBS as a treatment for advanced PD.

Numerous systematic reviews have demonstrated not only the prevalence of racial and gender biases among providers but also how these biases are associated with worsened patient outcomes [55‒57]. Research has suggested that diverse representation in the healthcare workforce may reduce bias, underscoring the importance of increasing diversity in neurosurgery to improve patient access [58]. Additionally, evidence across fields suggests that implementation of scientifically validated cultural competency training improves providers’ skills in providing culturally competent care, as well as patient satisfaction and follow-up [59‒61]. Continued efforts should be made to provide clinicians with education regarding disparities in healthcare, strategies to recognize and overcome biases, as well as approaches to communicate treatment options to patients in an equitable manner [62, 63].

Most currently available diversity, equity, and inclusion (DEI) educational materials cover broad topics encompassing all of medicine [64]. There may be an opportunity to enhance effectiveness and applicability of the material by focusing on specific disparities in medicine, such as disparities in procedures. For example, integrating information about disparities in access to DBS into continued medical education modules for physicians, particularly in primary care and neurology, could be an impactful approach to raise awareness and communicate directly with the individuals capable of making actionable change. There is some evidence to suggest that integration of DEI training into continued medical education modules may improve provider skills in providing culturally competent services and patient satisfaction [65, 66]. Previous studies have also found that incorporating DEI material into graduate medical education was feasible and well received [67]. Co-engagement with providers may also involve establishing regular forums or workshops to discuss case studies and share insights on reducing disparities. Within a limited context such as large academic medical centers, showing providers how their referral rates compare to that of their colleagues may also mitigate disparities [68].

A personalized approach involving effective clinician-patient communication is essential to understanding patient perspectives that may serve as barriers to care. Prior literature suggests that making information more easily accessible to all patients [69, 70], providing decision-making support, and engaging in shared decision-making with patients and their families may reduce disparities [71]. Given disparities in patient access to specialized providers such as neurologists [30, 39, 40], additional education on DBS and its risks and benefits should be targeted toward general practitioners; prior literature evaluating primary care referrals to specialists across multiple medical specialties suggests providing education and structured referral guidelines for primary care providers improves referral patterns [72]. Ultimately, healthcare providers should work to ensure that all patients, regardless of race, gender, and socioeconomic status, are provided with information about advanced treatment options such as DBS in a timely, factual, and unbiased manner.

Patient level interventions to reduce disparities in DBS access should include specialized educational materials. Poor health literacy is associated with lower rates of healthcare usage, leading to worse outcomes [73]. A systematic review found that approximately half of patients in the USA exhibit limited health literacy, with rates varying based on age, education, income, and race [74]. Surgical patients are considered a high-risk population due to the complexity of their pathologies and proposed interventions [75]. Numerous studies have shown that neurosurgical patients, particularly those from marginalized racial, gender, or socioeconomic groups, have a limited understanding of procedure-associated risks [76‒78]. Furthermore, inequities in access to digital health technologies and low digital health literacy pose a unique challenge to PD patients as this disease impacts cognition and disproportionately affects the elderly [79]. Multiple studies have found that low digital literacy is a barrier to the use of digital health resources, particularly in underrepresented racial or socioeconomic groups [80, 81]. Providing accessible and easy to understand information in a variety of formats may help address some of the factors that are preventing patients from undergoing DBS and contributing to disparities in access to this therapy [82, 83].

Providing personalized education may also help reduce disparities in DBS access. One study found that educational material, including an informational video specially developed to address patient concerns about DBS, was effective in increasing the number of patients who decided to proceed with surgery evaluation and may improve the likelihood of women undergoing surgery [84]. Additionally, a randomized controlled trial found that using a three-dimensional brain model for education during DBS consultation significantly improved patient understanding of the procedure [85]. Importantly, educational materials should be created in an unbiased manner that uses language appropriate for the intended audience. In the first of a two-part systematic review of patient education in neurosurgery, Shlobin et al. [86] found that written materials and internet resources were often too advanced for the layperson to understand and may contain incomplete information due to financial conflicts of interest; the authors argue the importance of personalizing education to patient-specific needs and baseline knowledge levels using techniques such as reviewing imaging and providing relevant education resources. In the second systematic review, Shlobin et al. [87] aimed to understand characteristic features of effective neurosurgical patient education interventions; they recommend providing a variety of educational materials to reinforce concepts with an emphasis on the use of online resources such as video and three-dimensional models when appropriate. Previous studies evaluating the quality of neurosurgical videos posted on social media sites and YouTube found that a majority of videos contained advertisement biases, inaccurate information, and lacked references [88, 89]. There is evidence to suggest that high quality educational videos may be more effective than other mediums in reducing preoperative anxiety and increasing postoperative satisfaction, emphasizing the value of individualized digital education materials [90]. Additionally, increasing education and awareness regarding PD and its treatment options may encourage earlier diagnosis, more accurate reporting of symptoms, and greater trust in medical professionals [91, 92].

Better understanding gender and race-related differences in PD symptomatology, experience and expression of symptoms, and progression may also reduce disparities in patient evaluation and selection for DBS. Black patients have been found to underreport motor symptoms compared to white patients, leading to delays in diagnosis and treatment [93]. Women are more likely than men to be rejected for DBS due to depression [8]. To further illustrate the importance of addressing patient-specific concerns, after a center switched from awake microelectrode guided to asleep MRI-guided DBS placement, the percentage of women undergoing DBS increased to match the general PD population [14], suggesting that considering patient-specific concerns in approaches to surgery may help reduce disparities. Further research into DBS referral rates for different sexes and races as well as the frequency with which patients of different groups decide to undergo versus decline DBS is key to developing tailored treatment approaches that may help improve equity in treatment [94].

Community-level interventions have the opportunity to address disparities both in referral patterns and in post-referral DBS utilization. Efforts should be made to improve overall health outcomes in minority communities, such as increasing access to preventative care and addressing social determinants of health; doing so may also increase DBS candidacy in said communities’ PD patients. Prior literature in PD has revealed that implementation of a community-based dancing program improved PD symptoms in patients [95]. Community partnerships have also been used in other healthcare settings to accomplish a similar goal: partnerships with religious groups and barber shops have been shown to be effective in disseminating healthcare information to various communities and even facilitating referrals [96‒98]. Such programs have been successfully implemented for diseases like SARS-CoV-2 and human immunodeficiency virus as well as for general health screening [96‒98]. Similar coalitions could be made with elderly communities and their families to improve community and individual-level awareness of PD and DBS and also help facilitate neurologist referrals.

In the field of pediatric neurosurgery, the Patient-Centered Outcomes Research Institute (PCORI) has funded studies in collaboration with the Bobby Jones Chiari and Syringomyelia Foundation [99], the Hydrocephalus Association [100], and the Lennox-Gastaut Syndrome Foundation [101]. These partnerships provide clinicians with invaluable insight into specific challenges that their patient populations face, paving the way for more targeted and efficacious interventions [102]. This community-engaged research framework has been employed by the Parkinson’s foundation to assess patient engagement in research, which may ultimately help more effectively capture the needs of the community and address factors that contribute to disparities [103]. This community-engaged research framework, with its focus on understanding patient needs and disparities, could be used to inform the development and implementation of DBS interventions tailored to address the specific challenges faced by diverse patient populations.

Interventions specific to PD and DBS could include programs providing support aimed at increasing access to specialists, such as movement disorder neurologists, in minority communities which may help address disparities in DBS referral patterns. In particular, mobile clinics have been shown to increase minority population access to care and improve outcomes in other specialties [104, 105]. Importantly, more than half of the patients that visit mobile health clinics are women or racial/ethnic minorities [104]. Therefore, a neurology mobile clinic could be used in initial PD evaluation prior to DBS referral and may be particularly useful for those patient populations who are affected by disparities in access to DBS. Combined, community-based interventions such as mobile clinics, direct community partnerships, as well as community wellness and exercise initiatives may all serve as methods to reduce disparities in DBS utilization as well as in medical care for PD.

Many disparities stem from broad sources requiring organizational or national-level changes for more widespread improvement to occur [106]. First, increased support for research on disparities in DBS access is necessary to identify root causes and evaluate potential interventions. Socioeconomic and cultural factors contributing to healthcare disparities have been previously addressed at a policy and organizational level by implementing policies and programs that promote equity in opportunities, access to economic resources, and overall health [107], as well as providing education and support to address cultural barriers to care [108]. Similar approaches may help reduce disparities in accessing DBS treatment. Additionally, we propose that increased representation of diverse individuals in the membership and leadership of neurology and neurosurgery societies and publication of guidelines addressing disparities in care may be instrumental in instigating change. Notably, organizational and policy adaptations should increase diversity not just of committees within national and international societies but also of PD and DBS providers. There are significant gender and racial disparities within the fields of both academic neurology [109, 110] and academic neurosurgery [111], with these disparities especially pronounced in neurosurgery. Previously proposed organizational interventions to increase diverse representation include targeted effort toward recruitment of racial minorities to neurosurgery and in leadership positions [112], enforcement of parental leave policies [112], and compensation equity [113]. Within academic institutions, efforts such as embracing holistic admissions approaches, leveraging social media platforms for tailored outreach to underrepresented ethnic and racial groups, and integrating diversity tracking tools such as a diversity dashboard have demonstrated effectiveness in improving diverse representation [114]. Given that there is evidence that nonwhite physicians disproportionately care for racial minority patients [115], it is critical to recruit women and racial minority physicians to specialty fields such as neurology and neurosurgery as this could help improve access to neurological and neurosurgical care such as DBS for minority populations.

Telemedicine may be another cost-effective organizational method to expand access to care for those living in distant or underserved areas. While it has been used in many specialties [116, 117], telemedicine alone may still be affected by disparities in access to and comfort with technology [118]. Additionally, streamlining the referral process and providing support for presurgical evaluations has been shown to help reduce the burden on referring physicians and encourage more referrals for DBS evaluations [72, 119, 120]. Effectively addressing disparities in DBS will also require increasing access to interpreter services [121], providing patient education materials in multiple languages, increasing social worker and case manager involvement in perioperative DBS care, and implementing policies to reduce bias and ensure equitable access to care [118]. Efforts to have diverse representation in marketing materials and to target underrepresented minorities may also help improve awareness of and access to DBS, as differences in exposure to direct-to-consumer marketing in healthcare between races have been previously observed [122, 123].

Finally, changes in reimbursement policies could help improve access to DBS. Research in otolaryngology has suggested that providers may avoid government-funded insurance due to lower reimbursement and increased administrative burden [52]. Given that Medicaid is independently associated with decreased DBS use [11], improved Medicaid reimbursement may effectively encourage more neurological and neurosurgical providers to accept Medicaid and improve access to specialized care in underserved communities [124‒126]. Additionally, although most insurances cover DBS for PD, the development of nationally accepted candidacy criteria for DBS may increase the equity of insurance coverage, particularly for lower income patients.

The aforementioned disparities and proposed solutions are summarized in Tables 2 and 3, respectively. Solutions are also graphically presented in Figure 2.

Gender, racial, and socioeconomic disparities can all contribute to unequal access to DBS treatment. Factors that contribute to these disparities are diverse and include factors impacting access to care, disparities in referrals to surgical providers, social and cultural factors, and financial limitations. Interventions on a provider, patient, community, and policy level are necessary to overcome these disparities. Ongoing research is important to quantify and raise awareness of disparities, while providing a foundation to develop tailored approaches to reduce them.

An ethics statement is not applicable because this study is based exclusively on published literature.

The authors have no conflicts of interest to declare.

This study was not supported by any sponsor or funder.

Data acquisition: A.E.B., S.B., A.T.L., and M.N.M.; interpretation of data: A.E.B., N.C.H., M.Z., D.L.P., S.B., and A.T.L.; writing – original draft: A.E.B., N.C.H., M.Z., D.L.P., S.B., A.T.L., and M.N.M.; revising – original draft: A.E.B., T.J.B., D.J.E., and S.K.B.; revisions: A.E.B., N.C.H., M.Z., and S.K.B.; study design and conception: A.E.B., D.J.E., and S.K.B. All authors approved the final version of this manuscript and are accountable for all aspect of the work.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.