Table 1.

Study characteristics of included articles

Author	Country	Number of DBS patients	Gender	Mean age, years	Most represented races	Disparity studied	Disparity observed	Proposed rationale
Shpiner et al. [6] 2019	USA (FL)	207 referred, 100 (48.3%) received surgery	Male: 75.8%	Male: 65.0	Caucasian: 83%	Gender	Women are less likely to receive DBS due to preference	Decreased preoperative education for women
			Female: 24.2%	Female: 65.3	African American: 4.8%
					Unknown: 4.8%
Watanabe et al. [7] 2022	USA (HI)	74	Male: 66.22%	N/A	White: 43.24%	AA and NHPI utilization of DBS	NHPI and black PD patients underrepresented. All NHPI receiving DBS were male	Lack of access to care in underserved minorities leading to earlier mortality
			Female: 33.78%		AA: 45.95%
Jost et al. [8] 2022	France	316 referred	Male: 67%	Male: 62.0	N/A	Gender	Fewer women underwent DBS assessment than expected, fewer referrals from physicians	Nonclinical factors such as referral biases, greater fear of surgery, or socioeconomic status
		190 (83.0%) received surgery	Female: 33%	Female: 62.7
Dalrymple et al. [9] 2019	USA (VA)	137	Male: 69.3%	Male: 63.3	N/A	Gender	Women were less likely to receive DBS for medication refractory tremor	Male preference for surgery or clinician bias leading to fewer referrals for women
			Female: 330.7%	Female: 63.3
Crispo et al. [10] 2020	Canada	260	Male: 74.6%	64.4	N/A	Age	Patients living in areas with a large minority population are less likely to receive DBS surgery	Differences in access to care, health-seeking behavior, or need for DBS
			Female: 25.4%
Chan et al. [11] 2014	USA	18,312	Male: 67.53%	63.66	White: 85.71%	African American access to DBS	African Americans with PD are 8 times less likely to undergo DBS relative to white patients	Medicaid reliance amongst black patients, access to care, or cultural biases
					Hispanic: 7.71%
			Female: 32.47%		Asian/PI: 2.50%
					African American: 0.86%
Skelton et al. [12] 2023	USA (GA)	209 referred	(Referrals)	64.1	(Referrals)	Utilization of DBS by black patients	Underutilization of DBS by black patients post-referral	Disparities occur in the time between medical management and surgical evaluation, driven by lack of patient follow-up
			Male: 73.2%		White: 84.7%
					Asian: 6.2%
		171 (81.8%) received surgery	Female: 26.8%		Black: 4.8%
					Hispanic: 4.3%
Willis et al. [13] 2014	USA	8,420	Male: 59.3%	Medicaid patients (>65)	White: 94.9%	Demographic, clinical, SES, and physician practice factors	Greatest disparities are associated with race: black and Asian patients were less likely to receive DBS than white patients. High neighborhood SES associated with greater odds of receiving DBS	Multidisciplinary care is not accessible in low-income areas. Lack of referrals in areas with a high minority population
					Unknown: 0.12%
			Female: 40.7%		Hispanic: 1.7%
					Black: 1.0%
Vinke et al. [14] 2022	Netherlands, Slovenia	121	Male: 64.5%	N/A	N/A	Gender	Women have a greater chance of undergoing DBS when an asleep MRI or CT guided method is available	Increased anxiety about surgery among women may make asleep operations more tolerable
			Female: 35.5%
Chandran et al. [15] 2014	India	51	Male: 62.7%	Male: 55.8	N/A	Gender	Women equally likely to undergo DBS	Financial considerations are main limitation for surgery in this population
			Female: 37.3%	Female: 54.5
Cramer et al. [16] 2022	USA	50,837	Male: 68%	64.3	White: 84.9%	Race and SES	Black patients were 5 times less likely to undergo DBS than white patients. Female patients were also less likely to receive DBS than males	Systemic factors such as unconscious/conscious bias
			Female: 32%		Other: 13.8%
					Black: 1.3%
Deuel et al. [22] 2023	USA	6,952	Male: 69.5%	Male: 65.2	N/A	Gender	Both national and local data were consistent with a gender disparity	Women with PD are more likely to live alone and more likely to have concerns over side effects
			Female: 30.5%	Female: 65.5
Sarica et al. [17] 2023	Canada	8,655	Male: 69.5%	65.1	White: 85.0%	Gender	Female and black patients are less likely to undergo DBS. Increasing SES is a positive predictor for DBS use	Biases both at the initial screening stage and during the assessment for surgery
					Hispanic: 6.8%
					African: 1.8%	Race
			Female: 30.5%		Asian: 2.6%
					Native American: 0.4%	SES
					Other: 3.4%