Perceived injustice mediates the relationship between socioeconomic status and physical function among individuals with chronic low back pain

Abstract

Chronic low back pain (CLBP) is among the most prevalent musculoskeletal pain conditions, accounting for the largest number of years lived with disability. A growing literature suggests that low socioeconomic status (SES) is associated with diminished physical functioning and increased physical limitations, antecedents for disability. Emerging evidence also suggests that pain-related perceived injustice is a risk factor for poor CLBP outcomes, including pain-related disability. Relatedly, maladaptive patterns of appraisal (e.g., perceived injustice) may be shaped by prior adverse social experiences, such as inequalities resulting from low SES. Thus, the purpose of this study was to examine whether perceived injustice mediates the relationship between income status (i.e., an indicator of SES) and physical function among individuals with CLBP. CLBP patients (N = 129) completed the Short Physical Performance Battery (SPPB), an objective measurement instrument of lower extremity functioning. Additionally, patients completed a series of questionnaires including study demographics, the Injustice Experience Questionnaire, the Center for Epidemiological Studies – Depression Scale, and the Brief Pain Inventory – Short Form. In a regression-based model adjusted for sex, racial/ethnic status, depression, and current level of pain severity, findings revealed that perceived injustice significantly mediated the association between income level and physical function [Indirect Effect = 0.02, 95% CI: 0.0005 to 0.06]. Specifically, lower level of income was associated with greater perceived injustice (p = 0.006), which in turn was associated with diminished physical performance (p = 0.02). This study is among the first to examine associations between socioeconomic status, perceived injustice, and physical function. Our findings suggest that injustice perception may be a mechanism through which income status impacts current physical function, which may potentially lead to long-term disability over time. These findings reinforce the importance of further examining injustice appraisals as targets for intervention, especially among low income individuals with CLBP. This research was supported by the National Institute on Minority Health and Health Disparities (Goodin).