Racial and Ethnic Disparities in Chronic Pain following Traumatic Injury

Dear Editor,

Chronic pain affects approximately 50 million adults (20.5%) in the U.S. and places a significant health and economic burden on individuals [1]. Furthermore, studies point to a higher chronic pain burden among Black and Latino adults compared to non-Latino Whites [2, 3]. The reasons for these disparities are not well understood, but some potential explanations include differences in the prevalence of diseases or types of injuries that contribute to chronic pain or unequal access to or utilization of pain treatments, among others [3, 4]. Thus, interventions aimed to reduce chronic pain disparities warrant a clear understanding of the extent to which any observed differences by race/ethnicity are due to other underlying differences. Specifically, it is important to account for potential differences in a group’s predisposition to developing chronic pain (e.g., having pre-existing pain) or broader disparities in exposure to hazardous environments that increase one’s risk of developing chronic pain. For example, compared to Whites, Black and Latino individuals experience higher rates of firearm injuries [5], a form of violence that promotes other factors that can worsen perceived pain such as emotional trauma.

Survivors of a severe traumatic injury, such as from violence or vehicle accidents, are at high risk of developing chronic pain [6] and account for about 40% of all discharges from Level I trauma centers [7]. Thus, trauma centers are an important point to intervene to prevent the subsequent development of chronic pain, particularly among the highest risk groups. Yet, few studies have investigated racial/ethnic disparities in pain following severe traumatic injury [8, 9]. Furthermore, no published study has distinguished the extent to which any observed racial/ethnic disparities in chronic pain following traumatic injury are attributed to other underlying disparities. Specifically, ignoring racial/ethnic differences in pre-injury pain or characteristics during the acute phase following injury (injury mechanism, injury severity, etc.), may produce an incomplete understanding of the sources of disparities in chronic pain. Therefore, the present study investigates the degree to which Black and Latino trauma center patients are at increased risk for higher chronic pain severity relative to White patients, controlling for group differences in pre-injury pain and a range of injury characteristics.

Methods

This analysis uses data from the Consequences of Traumatic Injury (COTI) study, a prospective study of pain disparities among a diverse sample of patients who were hospitalized for a new traumatic injury between November 2017 and May 2020 at one of two urban Level I trauma centers: Baylor University Medical Center (BUMC) in Dallas, Texas, or the Penn Presbyterian Medical Center of the University of Pennsylvania (Penn) in Philadelphia, Pennsylvania. The Institutional Review Boards of the RAND Corporation (Penn deferred to RAND IRB) and BUMC approved all study procedures. The study has a Certificate of Confidentiality from the National Institutes of Health.

Eligibility criteria included: aged between 18 and 65 years, suffered an acute physical injury not related to a preexisting condition or intentional self-harm, admitted to the hospital for at least 24 hours, and not in police custody. We randomly oversampled non-Latino White and Latino patients at Penn and Latino patients at BUMC, using race/ethnicity data from hospital admissions records. Across the two sites, 650 patients completed the baseline survey and were invited to complete the 3- and 12-month follow-up interviews. Baseline interviews were conducted more than 24 hours, but less than 2 weeks, after injury. Interviews were conducted in English or Spanish. All participants provided written informed consent.

An adapted version of the validated Brief Pain Inventory short-form (BPI-SF) [10, 11] assessed pain severity at 3- and 12-months follow-up. Participants rated their pain a) “right now,” b) “at its worst in the last 7 days,” c) “at its least in the last 7 days,” and d) “on average over the last 7 days” (response options: 0 = “no pain” to 10 = “pain as bad as you can imagine”). Responses were averaged.

Race/ethnicity was assessed with two separate items on Hispanic/Latino/Spanish ethnicity and race (American Indian or Alaska Native, Asian, Black or African American, Native Hawaiian or Pacific Islander, White, or other). Responses to both items were used to categorize individuals as Latino (regardless of race selected), non-Latino Black, or non-Latino White. Those who identified with any other race/ethnicity were grouped in an “other” category given the small sample size (total of 19). Covariates included age; sex; injury mechanism (interpersonal violence, vehicle collision, or falls or other); time between injury and each follow-up interview; and trauma registry variables, including Injury Severity Score (ISS), hospital length of stay, and hospital discharge destination. We also controlled for pre-injury pain severity, which was assessed at baseline with a modified BPI-SF [10] that dropped the item about pain “right now” and used “in the 30 days before the injury” timeframe in the three remaining questions about pain at its worst, at its least, and on average. Additionally, we controlled for acute injury pain severity, which was assessed at baseline using a modified BPI-SF [10] that also dropped the item about pain “right now” and retained the standard “in the last 24 hours” timeframe on the three remaining questions about pain at its worst, at its least, and on average.

We conducted separate linear regression models estimating the associations of race/ethnicity with the 3-month and 12-month pain severity outcomes. We conducted a series of models, introducing new covariate(s) in blocks.

Results

Table 1 shows the sample characteristics. At 3-month follow-up, compared to White patients, pain severity was significantly higher in Black patients, even after adjustment for all covariates (Table 2, model 4: b (SE) = 0.80 (0.26), P = .003). At 12-month follow-up, higher pain severity was observed among both Black (Table 2, model 4: b (SE) = 0.63 (0.29), P = 0.03) and Latino patients (Table 2, model 4: b (SE) = 0.61 (0.30), P = .04) compared to White patients, after adjusting for all covariates.

Table 1.

Characteristics of the traumatic injury patient sample, overall and by race/ethnicity

	All	Non-Latino White	Latino	Non-Latino Black	Other race
	(n = 650)	(n = 218)	(n = 166)	(n = 247)	(n = 19)
Individual characteristic
Age in years, mean (SD)	40.0 (14.2)	43.4 (14.5)	35.5 (13.2)	39.8 (13.9)	41.8 (12.7)
Male, %	68.0%	59.6%	74.1%	71.7%	63.2%
Site: Baylor, %	49.9%	46.8%	84.3%	31.6%	21.1%
Pre-injury pain severity, mean (SD)	1.5 (2.2)	1.6 (2.0)	1.2 (1.9)	1.7 (2.6)	1.6 (2.3)
Injury-related pain severity scores
Baseline (acute), mean (SD)	6.3 (2.1)	5.5 (2.0)	6.2 (2.1)	7.0 (1.9)	6.6 (2.2)
3-month, mean (SD)	3.1 (2.5)	2.4 (2.1)	2.5 (2.3)	3.9 (2.6)	4.0 (2.8)
12-month, mean (SD)	3.0 (2.7)	2.2 (2.2)	2.7 (2.5)	3.8 (2.9)	3.6 (3.4)
Other injury factors
Injury Severity Score,* mean (SD)	10.0 (7.7)	10.1 (6.8)	10.7 (8.8)	9.4 (7.4)	11.5 (9.3)
Hospital length of stay in days,* mean (SD)	6.6 (6.1)	6.1 (4.6)	6.8 (6.7)	6.8 (6.9)	6.8 (4.7)
Discharged to home,* %	78.6%	73.4%	87.0%	76.3%	94.7%
Injury mechanism, %
Interpersonal violence	25.5%	8.3%	22.9%	42.1%	31.6%
Vehicle collision	42.0%	43.6%	48.8%	36.8%	31.6%
Falls or other mechanism	34.2%	50.5%	30.1%	22.3%	36.8%

^*Variables are from the trauma registry.

Table 2.

Associations of race/ethnicity with 3- and 12-month pain severity among trauma injury patients

	Outcome: 3-month pain severity
Predictor	Model 1*		Model 2*		Model 3*		Model 4*
	b (SE)	P	b (SE)	P	b (SE)	P	b (SE)	P
Race/ethnicity (ref: non-Latino White)
Latino	0.14 (0.29)	.64	0.43 (0.31)	0.16	0.43 (0.29)	0.14	0.17 (0.29)	.55
Non-Latino Black	1.50 (0.26)	<.001	1.51 (0.26)	<0.001	1.41 (0.25)	<0.001	0.80 (0.26)	.003
Other	1.61 (0.59)	.01	1.51 (0.59)	0.01	1.50 (0.56)	0.01	1.04 (0.54)	.06
R2	0.09		0.10		0.21		0.29

	Outcome: 12-month pain severity
	Model 1*		Model 2*		Model 3*		Model 4*
	b (SE)	P	b (SE)	P	b (SE)	P	b (SE)	P
Race/ethnicity (ref: non-Latino White)
Latino	0.43 (0.31)	0.17	0.88 (0.33)	0.01	0.87 (0.31)	.01	0.61 (0.30)	.04
Non-Latino Black	1.56 (0.29)	<0.001	1.61 (0.29)	<0.001	1.40 (0.27)	<.001	0.63 (0.29)	.03
Other	1.35 (0.75)	0.07	1.17 (0.74)	0.12	1.15 (0.69)	.10	0.72 (0.66)	0.28
R2	0.07		0.10		0.22		0.33

Bolded values are significant at P < .05.

^*Model 1 includes race/ethnicity and time (square root of days between injury and follow-up interview date); Model 2 additionally adjusts for age, sex, and site (Baylor vs Penn); Model 3 additionally adjusts for pre-injury pain severity; Model 4 additionally adjusts for acute pain severity, injury mechanism (reference: falls or other), Injury Severity Score, hospital length of stay, and hospital discharge destination (home vs other).

Discussion

The present study is one of the first specifically designed to investigate the development of racial/ethnic disparities in post-injury chronic pain. In this sample of traumatic injury survivors, we found evidence of chronic pain disparities, with Black and Latino patients reporting higher pain severity at 3- and 12-months post-injury, compared to White patients. These findings are consistent with the broader literature pointing to racial/ethnic disparities in chronic pain among general and clinical populations [3, 4]. Findings suggest that these racial/ethnic disparities are not fully explained by differences in predisposition to pain (i.e., pre-injury pain or acute pain immediately following injury) or disparities in injury mechanisms.

Strengths of our study include the prospective design with a racially/ethnically diverse sample across two diverse urban areas and the use of self-report and objective trauma registry data to account for predisposing and injury risk factors. However, findings are not generalizable to other trauma centers. Furthermore, it is important to note that although the observed racial/ethnic differences are statistically significant, future investigation should examine the clinical significance of these differences (impact on related outcomes) and to what extent intervention mitigates these differences. Additional research is needed to identify interventions that can mitigate these disparities, including those that address clinical, socioeconomic, or cultural factors that impede recovery from trauma or that facilitate the development of chronic pain.

 

Funding sources: This work was funded by the National Institute on Minority Health and Health Disparities (R01MD010372).

Conflicts of interest: The authors have no relevant financial or non-financial interests to disclose.