Why Do Native American Adults Have Higher Rates of Chronic Pain?

Compared with non-Hispanic White adults, Native American adults have 4 times the rate of chronic pain, with psychosocial factors, such as stress, as a partial mediator. These are the findings of a study published in the journal Pain.

In the United States, Native American adults experience higher rates of chronic pain than other racial and ethnic groups. However, mechanisms possibly underlying this inequity are misunderstood.

To explore this issue and to identify prospective predictors of chronic pain onset, investigators conducted a 5-year follow-up analysis of the Oklahoma Study of Native American Pain Risk (OK-SNAP) study. They followed a multipronged approach to recruit healthy, pain-free Native American and non-Hispanic White adults between March 2014 and October 2018. This approach allowed them to identify participants who developed chronic pain over time and analyze its occurrence.

Laboratory testing was conducted over a period of 2 days in 2 laboratory visits lasting 4 to 6 hours each; multiple tests were performed to assess pain sensitivity and pain modulation. Using patient surveys, the investigators assessed mechanisms consistent with the biophysical model of pain, collecting information on demographics, on physical differences including cardiometabolic variables, on psychosocial factors, and on nociceptive phenotypes. Patients who completed at least 75% of 1 laboratory testing day were deemed eligible to complete follow-up surveys every 6 months for 60 months.

A total of 277 patients (non-Hispanic White, 142; Native American, 135) completed follow-up surveys every 6 months. Data for the 250 participants (90%) who completed at least 1 follow-up during the 60-month post enrollment period are included in the current post hoc analysis, which covers results of all follow-up from 6 to 60 months.

Beginning at the 24-month follow-up mark, the number of participants in each of the 2 study groups who completed health surveys every 6 months had dropped by approximately half, although this did not reflect dropout/attrition but instead reflected inconsistent responses to various follow-up requests.

By the 2-year follow-up visit, chronic pain was more likely to develop in Native American individuals vs non-Hispanic White individuals. Partial potential mediators of this inequity were identified; these included psychosocial factors such as discrimination, stress, and pain-related anxiety; differences in cardiometabolic load caused by higher BMI, higher blood pressure, and less heart rate variability; and impaired inhibition of spinal nociception. After controlling for baseline age, sex assigned at birth, income, and education, compared with non-Hispanic White adults, those who identified as Native American were approximately 3 times more likely to develop chronic pain (odds ratio [OR], 2.9).

To further explore the mechanisms of racial inequity in chronic pain, the investigators analyzed data collected at the 5-year follow-up in OK-SNAP, which included 250 (approximately 90%) of the initial 277 patients. They found that, even after controlling for baseline age, sex assigned at birth, income, and education, at 5 years Native American individuals were 4 times more likely (OR, 4.25; 95% CI, 1.966-8.239) to develop chronic pain than non-Hispanic Whites. At the 5-year follow-up, chronic pain at any site was experienced by 12% of non-Hispanic White vs 28% of Native American individuals; these rates are twice as high as those reported at the 2-year follow-up.

Serial mediation models were used to confirm the partial mediators of chronic pain onset found at the 2-year follow-up. Analysis of 5-year follow-up data associated discrimination, stress, sleep problems, and increased pain perception with greater risk that chronic pain would develop. It also associated discrimination with the finding that Native American adults had a higher spinal nociceptive threshold and greater risk for experiencing pain.

Study limitations included the potential underestimation for pain inequity, owing to difference in follow-up and the inability to determine the directionality of the associations due to the prospective assessment of chronic pain onset, with predictors collected 5 years ago. Additionally, other important predictors (eg, inflammation, diet, endogenous opioids) may have been overlooked, and medication use changes were not assessed in follow-up surveys, which could have affected assessment and classification of chronic pain.

“At the 5-year follow-up, NAs [Native Americans] developed chronic pain at 4 [times] the rate of NHWs [non-Hispanic Whites],” the researchers wrote. They added, “These results provide further evidence for a Native American pain inequity and identify multiple psychosocial, cardiometabolic, and pronociceptive targets for primary interventions.”

This article originally appeared on Clinical Pain Advisor