Although several factors are known to contribute to ethnic differences in pain, relatively little attention has been devoted to physiological factors. Our first aim was to examine the relationship between cortisol and pain responses during a cold-pressor task (CPT) among African American (AA) and non-Hispanic White (NHW) adults with knee osteoarthritis (OA). Our second aim was to assess the relationship between perceived racial discrimination and cortisol among AA participants.
Participants were 91 (56 AA; 35 NHW) community-dwelling adults between the ages of 45 to 85 with knee OA based upon the American College of Rheumatology clinical criteria. Plasma cortisol was measured at 3 timepoints: (1) baseline, (2) before the CPT, and (3) 20 minutes following the CPT. Perceived racial discrimination was measured by the Experiences of Discrimination scale.
Using linear regression, we found a significant interaction between ethnicity and cortisol before the CPT with pain intensity ratings (β=−0.26; P=0.02). Analysis of simple slopes revealed that cortisol concentrations were negatively associated with pain intensity ratings in NHW participants (β=−0.54; P=0.001), but not in AA participants (β=−0.15; P=0.26). Perceived racial discrimination was not related to cortisol concentrations or pain ratings.
Consistent with previous findings in young healthy adults, cold-pressor pain responses are related to pre-CPT cortisol concentrations in NHW persons with knee OA but not in their AA counterparts. Additional studies are required to better understand this finding.
*Center of Excellence for Stress and Mental Health (CESAMH)
†VA San Diego Healthcare System, University of California, San Diego, CA
‡Department of Psychology, University of Alabama at Birmingham
§Division of Clinical Immunology & Rheumatology, University of Alabama at Birmingham, Birmingham, AL
∥College of Nursing & Health Innovation, Arizona State University, Phoenix, AZ
¶Department of Community Dentistry and Behavioral Science, University of Florida
#Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL
Supported by the National Institutes of Health/National Institute on Aging (R01AG033906), the University of Florida Clinical and Translational Science Institute (UL1TR000064, R.B.F), and the University of Alabama at Birmingham Clinical and Translational Institute (UL1TR000165). M.E.H. received support from the Agency for Healthcare Research and Quality (5 T32 HS013852-09) and the National Institute on Minority Health and Health Disparities (3 P60 MD000502-08S1). The authors declare no conflict of interest.
Reprints: Matthew S. Herbert, PhD, VA San Diego Healthcare System, University of California, San Diego, 3350 La Jolla Village Drive (116B), San Diego, CA 92161 (e-mail: firstname.lastname@example.org).
Received July 7, 2016
Received in revised form January 19, 2017
Accepted November 19, 2016