A quantitative review of ethnic group differences in experimental pain response: do biology, psychology, and culture matter?

Abstract

Objective: Pain is a subjectively complex and universal experience. We examine research investigating ethnic group differences in experimental pain response and factors contributing to group differences.

Method: We conducted a systematic literature review and analysis of studies using experimental pain stimuli to assess pain sensitivity across multiple ethnic groups. Our search covered the period from 1944 to 2011, and used the PubMed bibliographic database; a reference source containing over 17 million citations. We calculated effect sizes; identified ethnic/racial group categories, pain stimuli, and measures; and examined findings regarding biopsychosociocultural factors contributing to ethnic/racial group differences.

Results: We found 472 studies investigating ethnic group differences and pain. Twenty-six of these met our review inclusion criteria of investigating ethnic group differences in experimental pain. The majority of studies included comparisons between African Americans (AA) and non-Hispanic Whites (NHW). There were consistently moderate to large effect sizes for pain tolerance across multiple stimulus modalities; AA demonstrated lower pain tolerance. For pain threshold, findings were generally in the same direction, but effect sizes were small to moderate across ethnic groups. Limited data were available for suprathreshold pain ratings. A subset of studies comparing NHW and other ethnic groups showed a variable range of effect sizes for pain threshold and tolerance.

Conclusion: There are potentially important ethnic/racial group differences in experimental pain perception. Elucidating ethnic group differences has translational merit for culturally competent clinical care and for addressing and reducing pain treatment disparities among ethnically/racially diverse groups.

Figure 1

Effect Sizes for Ethnic Group Differences in Heat Pain Responses for studies Comparing African American (AA) to non-Hispanic White (NHW) Subjects. Bars reflect Cohen’s d. Bars greater in length to the left indicate greater values for NHW compared to AA, while bars increasing in length to the right indicate greater values of that measure for AA vs. NHW. Greater values for pain threshold and pain tolerance reflect lower pain sensitivity, while greater values for pain ratings indicate higher pain sensitivity. * The Edwards and Fillingim effect sizes are difficult to interpret as these values reflect differences in the slope of the stimulus response function, rather than differences in heat pain ratings. (Unpl)=unpleasantness ratings; (Int)=intensity ratings.

Figure 2

Effect Sizes for Ethnic Group Differences in Cold Pain Responses for studies Comparing African American (AA) to non-Hispanic White (NHW) Subjects. Bars reflect Cohen’s d. Bars greater in length to the left indicate greater values for NHW compared to AA, while bars increasing in length to the right indicate greater values of that measure for AA vs. NHW. Greater values for pain threshold and pain tolerance reflect lower pain sensitivity, while greater values for pain ratings indicate higher pain sensitivity.

Figure 3

Effect Sizes for Ethnic Group Differences in Ischemic Pain Responses for studies Comparing African American (AA) to non-Hispanic White (NHW) Subjects. Bars reflect Cohen’s d. Bars greater in length to the left indicate greater values for NHW compared to AA, while bars increasing in length to the right indicate greater values of that measure for AA vs. NHW. Greater values for pain threshold and pain tolerance reflect lower pain sensitivity, while greater values for pain ratings indicate higher pain sensitivity. (Unpl)=unpleasantness ratings; (Int)=intensity ratings.

Figure 4

Effect Sizes for Ethnic Group Differences in Electrical and Mechanical Pain Responses for studies Comparing African American (AA) to non-Hispanic White (NHW) Subjects. Bars reflect Cohen’s d. Bars greater in length to the left indicate greater values for NHW compared to AA, while bars increasing in length to the right indicate greater values of that measure for AA vs. NHW. Greater values for pain threshold and pain tolerance reflect lower pain sensitivity, while greater values for pain ratings indicate higher pain sensitivity. (PPT-T)=Pressure Pain Threshold-Trapezius; (PPT-M)=Pressure Pain Threshold-Masseter.