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8 Articles in this Series
Introduction
Bench to Bedside: Clinical Tips From APS Poster Presentations
New Pain Research Underscores the Importance of Sufficient Rest
The Benefits of Exercise for Pain Management
Exercise as Postoperative Analgesic?
How Race Affects Pain
Increased Centralized Pain in African American Patients
Managing Post-Tonsillectomy Pain in Obese Children
Research Offers Insight Into Fibromyalgia and Pain

Increased Centralized Pain in African American Patients

A popular hypothesis about why African American (AA) patients experience greater pain suggests that AA patients have a marked increase in central sensitization (CS), according to a presentation by researchers from Johns Hopkins University in Baltimore, Maryland, at the American Pain Society's annual meeting.

The experience of pain among African Americans may differ from non-Hispanic Whites.Centralized pain is known to influence nociceptive hyperexcitability, which would help explain why AA patients report more amplified pain responses than non-Hispanic (NHW) white patients. A recent analysis detailed the results of a series of sensory tests performed on an ethnically diverse cohort.1

Part of a larger knee osteoarthritis clinical trial, the cohort of 144 KOA patients (n = 56 AA, 86% female and n = 88 NHW, 67% female) performed an extensive pain evaluation, with following univariate analyses. The study found that AA patients had significantly heightened pain (P = 0.047) and CS (P = 0.009) compared to NHW patients.

CS, in particular, “significantly mediated ethnic differences in clinical pain” after controlling for other factors that have been related to disparities in pain perception, like sex, depression, catastrophizing, and sleep fragmentation, the authors noted.

Indeed, future research could benefit from exploring whether central sensitization may be a relevant risk factor for the development of chronic pain conditions. However, it also could be possible an entirely different explanation is at play, the authors wrote.

Aforementioned variables, especially behavioral and psychological factors, may better explain the racial differences found in pain experience between and AA and NHW patients. A second study, presented by Hailey Waddell Bulls, MA, of University of Alabama at Birmingham,  reported data suggesting both depressive symptoms and sleep fragmentation could be prime facilitators of these apparent racial differences in endogenous pain facilitation.2

The study didn’t focus on chronic pain sufferers, however. Researchers instead looked at a cohort of 50 community-dwelling adults (n = 26 AA, n = 24 NHW; mean age 50 years [range 22 to 77 years]) with no chronic pain issues and had the participants complete the Center for Epidemiological Studies Depression Scale (CES-D) before monitoring their sleep, using actigraphy over the seven following nights. Participants were then given a mechanical temporal sensation protocol to examine their endogenous pain facilitation.

The results supported the notion of a “three-path mediation model” (95% Confidence Interval: -2.325 to -0.086), whereby AA race associated with greater depressive symptoms (t = -2.08, p = .043), which in turn associated with poorer sleep efficiency (t = -2.55, P = 0.014), which then associated with augmented temporal summation of mechanical pain (t = -4.11, P < 0.001), the authors reported.

“This study lends support for the negative impact of depressive symptoms on sleep efficiency, and suggests that both sequentially mediate racial differences in endogenous pain facilitation.” Therefore, interventions aimed at reducing depressive symptoms and improving sleep efficiency could have a measurable impact on AA patients suffering from CS, the authors wrote.

Catastrophizing May Also Play a Role in Sensitization

However, depression and sleep loss may not be the only behavioral factors to consider when investigating endogenous pain mechanisms. Another study presented at this year’s APS meeting found AA patients suffering from osteoarthritis (OA) reported significantly higher levels of pain and catastrophizing scores.3

Pain catastrophizing (Cat) is a negative form of thinking, where patients ruminate and exaggerate their pain symptoms, oftentimes habit-formed cognitions that have been shown to significantly affect pain perception.

In the study, researchers lead by Janiece Walker, PhD, RN,  of Johns Hopkins University, examined 143 OA patients (n = 56 AA, n = 88 NHW; mean age 60.8 [SD = 9.9]), measuring the patients pain using the Western Ontario & McMaster Universities Osteoarthritis Index (WOMAC) and catastrophizing scores using the Pain Catastrophizing Scale (PCS).

The researchers found AA patients reported significantly different pain and catastrophizing scores compared to NHW patients (P < 0.05), where race was associated with pain (b = -9.55, SE = 4.00, p < .05), and this relationship was being mediated by catastrophizing (b = 0.69, SE = 0.35, P < 0.05).

 

References

1.     Walls T, Campbell C, Robinson M, et al. Ethnic differences in central sensitization among patients with knee osteoarthritis. Poster presented at: Annual Meeting of the American Pain Society; May 11-14, 2016; Austin, Tx. Poster #320.

2.     Bulls H, Lynch M, Owens M, et al. Depressive symptoms and sleep efficiency mediate racial differences in endogenous pain facilitatory processes. Poster presented at: Annual Meeting of the American Pain Society; May 11-14, 2016; Austin, Tx. Poster #240.

3.     Walker J, Campbell C, Buenaver L, et al.  Race, pain and pain catastrophizing among African Americans and non-Hispanic Whites with osteoarthritis pain. Poster presented at: Annual Meeting of the American Pain Society; May 11-14, 2016; Austin, Tx. Poster #537

 

Next summary: Managing Post-Tonsillectomy Pain in Obese Children
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