Parkinson's disease (PD), the world's fastest-growing neurodegenerative disease, is a progressive condition characterized by motor and non-motor manifestations. The incidence of PD in the US appears to be similar amongst White and Hispanic/Latino peoples (for simplicity, we will use “Hispanic”; De Lau and Breteler, 2006; Aamodt et al., 2023), defined as Spanish-speaking people of Central and South American origin. Nevertheless, the best predictors for optimal care are high social and economic level, marital status, urban living, and being White (Ojukwu et al., 2021). Within the US Hispanic community, which often has incomes below the national median, management of motor and non-motor PD symptoms lags behind that of White non-Hispanic patients. In addition, the participation of Hispanic patients with PD in clinical trials is disproportionately low, with percentages varying from 1.6 to 5.4% (Schneider et al., 2009; Kurlawala et al., 2021), despite Hispanics representing at least 18% of the US population (De Lau and Breteler, 2006). This discrepancy may reflect limited healthcare access or underutilization of healthcare services, social and economic disadvantages, and cultural perception of PD manifestations (Duarte Folle et al., 2023). Unless we address this critical gap, the generalizability and validity of trial results in PD will remain limited, and Hispanic patients with PD will remain caught in a vicious cycle of inadequate care. This is rather crucial, as the Hispanic population is one of the fastest-growing demographic groups, fueled by factors such as immigration, higher birth rates, and a youthful population. A notable increase in life expectancy parallels this demographic trend, thus increasing the urgency to devise ways for greater access to care and participation in clinical trials of Hispanic patients with PD. Here, we first review the evidence of healthcare gaps in Hispanic patients with PD, studies underlying their low participation in research, and the attempts to foster their engagement in clinical trials. We then describe a possible model to address these problems based on the experience of recent initiatives by the Parkinson's Foundation.

Several analyses of available data sets have now provided evidence that Hispanic patients with PD may receive inadequate quality of health care compared to White non-Hispanic patients. As an example, a recent review of discharge data (from 2012 to 2018) of the National Inpatient Sample, Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality showed that, among many healthcare inequities, Hispanic patients with PD are less likely to be treated with deep brain stimulation than White patients (Dorritie et al., 2023), confirming earlier findings (Willis et al., 2014). Also, there are only a few clinical studies or trials focused on Hispanic patients with PD, and only in one of them, which combined two cohorts followed for a few years in two different periods in California, Hispanic patients were present in representative proportion (18%, corresponding to N = 138; Duarte Folle et al., 2023). That longitudinal study showed that in Hispanic patients, PD symptoms and signs appear at a younger age, progress faster in terms of the Hoehn & Yahr scale, and are, on average, more severe compared to their non-Hispanic counterparts (Duarte Folle et al., 2023). Moreover, studies indicate that in a large proportion of Hispanic patients, little or no drug adjustment occurs with the progression of the symptoms (Duarte Folle et al., 2023), even though changes in pharmacological treatment can improve life quality, prevent comorbidities and delay disability. This suboptimal therapeutical management may stem from a lack of financial resources, language and cultural obstacles, and difficulty in accessing adequate medical facilities, prescriptions, and medications. Indeed, studies have found that Hispanic patients with PD are 40% less likely to seek neurological care (Saadi et al., 2017) and in particular, to be cared for by a movement disorders specialist (Willis et al., 2011). This population also has lower access to nursing facilities than White non-Hispanic patients (Kumar et al., 2024). Altogether, these care differences may account for faster time to disability and earlier age at death in Hispanic patients with PD (Duarte Folle et al., 2023). Since the Hispanic population is the fastest growing in the U.S., as per the 2020 Census, finding strategies to improve quality and access to movement disorder care is imperative.

The impact of PD extends beyond motor symptoms. Depression is a frequent non-motor symptom of PD that may precede the appearance of motor symptoms. Notably, depression is more frequent and severe in Hispanic than in White non-Hispanic patients with PD (Duarte Folle et al., 2023; Jones et al., 2023), a finding in line with the fact that people of Hispanic origin display the highest rates of depression compared to non-Hispanic populations (Hooker et al., 2019). The higher depression rate in Hispanic PD patients can be accounted for by the lower use of antidepressant drugs (Cheng et al., 2008; Duarte Folle et al., 2023), thus pointing to underutilization of medical services of Hispanic people, another potential gap in their healthcare quality. Importantly, reduced care for depression significantly increases the risk of developing other non-motor signs of PD, such as cognitive impairment (Babulal et al., 2022). Indeed, a study following for some years a substantial number of Hispanics with PD, reported that Hispanic patients with PD had lower scores in cognitive tests (Duarte Folle et al., 2023). These gaps in healthcare quality likely have significant negative impacts on the Hispanic patient population.

In summary, Hispanic patients with PD, on average, experience lower quality of clinical care, including delayed diagnosis, poorer care, and inadequate treatment for both motor and non-motor symptoms. Limited access to proper healthcare, social and economic disadvantage, language barrier, and perception of both the disease's clinical manifestations and the healthcare environment may be the major contributors to healthcare problems in PD. These observations highlight the inadequate care of Hispanic patients with PD and the critical need to develop strategies to improve their use of the healthcare system.

According to the 2020 Census, Hispanic people living in the US were about 62 million (18.9% of the population), the second largest racial or ethnic group after White non-Hispanic people. The Hispanic group includes persons of Mexican, Puerto Rican, Central or South American, Cuban, or other Spanish culture or origin, regardless of race. Mexicans are highly represented with 61.6%, followed by Puerto Ricans (9.6%), Central Americans (9.3%), South Americans (6.4%), other Hispanics (including Spanish; 5.8%), and Cubans (3.9%). New York State, our base of work, has the fourth largest Hispanic population in the United States, with more than 2.4 million in New York City (more than 25%) and 4.8 million in the metro area. Considering areas that are part of the larger New York region up the Connecticut coastline, the number increases to 5.3 million, representing 22% of the region's population. The distribution of the Hispanic population in New York City includes, in decreasing order, Puerto Ricans and Dominicans, followed by Mexicans, Guatemalans, Salvadorians, Ecuadorians, and other origin, with no group reaching a clear majority. Importantly, according to the population estimate of the US Census of July 2022, Hispanic people represented more than 56% of the total population.

Most publications suggest that Hispanic and White non-Hispanic peoples have a similar incidence of PD (i.e., 1% of people older than 60 years; Van Den Eeden, 2003; De Lau and Breteler, 2006). Thus, based on the demographics outlined above, 20% of the participants in clinical trials for PD should be Hispanic patients. Yet, Hispanic research engagement is much lower, with most studies not defining all populations' characteristics. Indeed, a meta-analysis of 239 clinical trials in PD found that only 33 studies—for a total of almost 7,500 participants—specified all populations' characteristics (Schneider et al., 2009). Notably, only eight of the 33 studies included Hispanics/Latinos, for a total of 27 patients, with percentages varying from 1.6 to 5.4% (Schneider et al., 2009), in line with the 2.8% rate of Hispanic participants recruitment observed in the large-scale Parkinson's Progression Markers Initiative (PPMI) multisite study (Kurlawala et al., 2021). Most recently, two clinical trials, the Steady-PD III and the SURE-PD3, were not more successful in recruiting Hispanic participants despite the explicit use of direct or indirect incentives for enrolment: in both studies, only 2.9% of the participants were Hispanics (12 out of 413 and 17 out of 585, respectively; Di Luca et al., 2023). These findings show that, based on ethnic/racial population composition, the recruitment rate of Hispanics in the US is far below expectations, thus lessening the generalizability and validity of the results for persons with PD.

Why is fostering Hispanic patients' enrollment in clinical trials so difficult? While translating study and recruitment materials into Spanish overcomes the language barrier, other factors, such as different views about aging, family involvement, and perception of disease, are in play. The low involvement of Hispanic patients in clinical trials is likely linked to healthcare gaps and their possible causes, as illustrated above. Several studies have used strategies to address social barriers, such as language problems, yet with scant results. To effectively increase the involvement of Hispanic patients in clinical trials, other factors beyond language barriers need to be addressed, such as low healthcare literacy, mistrust in the healthcare system, investigators, and sponsors, lack of clinical trial awareness, poor communication; ineffective recruitment tools, and the concerns associated with disease (Adrissi and Fleisher, 2022; Vaswani et al., 2020; Picillo et al., 2015; Fleisher et al., 2014; George et al., 2014). The picture is further complicated by the patient's difficulty in accessing specialized movement disorders centers, together with a growing paucity of neurologists and movement disorders experts. Therefore, there is an urgent need to develop strategies for effective recruitment and retention of Hispanic patients with PD.

Recent studies have assessed strategies to increase and diversify recruitment for PD clinical studies. For example, Fox Insight used web-based digital marketing campaigns to increase Hispanic participation and the participation of people of lower educational and social and economic levels (Dobkin et al., 2020). It has been suggested that the continuous use of newsletters, social media, and PD-related websites—methods defined as “passive recruitment” tools—must be coupled with the so-called “active recruitment” methods that include networking with local clinicians or other health providers, outreach during PD support groups, and partnerships with community organizations (Picillo et al., 2015). Indeed, changing the environment of the recruitment from the clinic/hospital to more familiar surroundings (Nwabuobi et al., 2019; Fleisher et al., 2018), and directly involving the family with appropriate approaches and language settings (Damron et al., 2021), create a better foundation for building relationship, facilitating trust, and addressing most concerns. Also, engaging community stakeholders, such as those in religious centers, barbershops, beauty parlors, and community centers, can foster recruitment and retention in all communities (Jones and Wells, 2007; Levkoff and Sanchez, 2003; Mensah et al., 2018). In addition to the utilization of community opinion leaders and patient advocates during recruitment and, if possible, early in the study design (Feeney et al., 2020), community physicians, such as internists, primary care physicians, and neurologists, undoubtedly can play an important role. Thus, strategies for effective recruitment and retention of Hispanic patients with PD must be designed to involve community physicians and consider their time, resources, as well as patient concerns (Ison et al., 2024). Such strategies may include supporting research coordinators and implementing local training and educational events for physicians (Tilley et al., 2012).

Together, these studies and observations support the development of strategies that integrate clinical research within the patients' local community and milieu to increase the possibility of recruiting and retaining more Hispanic patients with PD in clinical trials and improve their access to optimal PD care.

People with PD who identify as Hispanic or Latino have been under-resourced not only in Spanish-language education on PD but also in Spanish-speaking providers and support services. The Parkinson's Foundation has been serving Spanish-speaking people with PD for more than 20 years, establishing a variety of programs and resources to better reach people of the Hispanic community, remove obstacles to care, open research participation, and ensure that information and resources are easy to find for all (for example, see: https://www.parkinson.org/espanol). The proposed model (see Figure 1) is based on three main activities: the training of the promotores de salud; the identification of needs and priorities of patients and caregivers with surveys and focus groups within the Hispanic communities, and feedback from Hispanic patients about their participation in research.

The proposed approach will provide a greater understanding of the challenges associated with fostering Hispanic patient participation in clinical trials for PD and a working model for outreach, awareness, education, and recruitment for clinical PD studies in the Hispanic communities. Importantly, this approach could also be adapted for reaching other communities. Those in the Hispanic community suffering from PD are disproportionately impacted by the disease symptoms while at the same time being inadequately represented in clinical research. The development of this research engagement model in the Hispanic population will not only provide local infrastructure for outreach and clinical studies, such as the genetic studies proposed in the PD GENEration (Cook et al., 2023), but, most importantly, has the potential to become the means to educate patients and implement better clinical care for all communities and groups. Furthermore, this program can establish sustainable partnerships with community-based organizations to empower patients, promote research efforts, and disseminate knowledge about PD. Altogether, these strategies may become essential tools for improving Hispanic patients' health, enhancing their quality of life, and promoting initial steps toward universal PD care.