Getting to Know Pain Effect Sizes-Guidelines for Effect Size and Sample Size in Global Pain Research.

OBJECTIVES

To explore potential reference thresholds for individual and group differences in pain research. An additional objective was to examine possible variations in these thresholds across geographic regions and to provide indicative estimates of the sample sizes that may be required to detect given effect sizes at specified levels of statistical power.

DESIGN

Data were exported from 6 key journals in the field of pain.

SETTING

Data were collected from 6 journals with the highest H-index according to the Scimago Journal & Country Rank database in the category of Anesthesiology and Pain Medicine.

PARTICIPANTS

In total, 130 meta-analyses were identified, from which 5294 effect size measures were extracted, encompassing a total of 1,071,577 participants.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Empirically derived effect size thresholds intended to support more nuanced interpretation of individual and group differences in pain research, with consideration of potential regional variability across populations.

RESULTS

Effect size thresholds were established based on percentiles, with small, medium, and large effects rounded to 0.10, 0.30, and 0.40 for correlations and 0.70 for group differences, respectively. Regional analyses revealed notable geographic variation, with the strongest large effects found in Asia and the weakest across studies conducted in North America.

CONCLUSIONS

Researchers may consider using approximate reference values of 0.10, 0.30, and 0.40 for individual differences (Pearson's r) and 0.10, 0.30, and 0.70 for group differences (Cohen's d or Hedges' g) as tentative interpretive guidelines for small, medium, and large effects in pain research, alongside appropriate sample size planning. For studies conducted within relatively homogeneous populations on individual continents, the following exploratory thresholds may be considered: Africa (0.10, 0.40, and 1.00); Asia (0.10, 0.40, and 1.40); Australia (0.20, 0.40, and 0.80); Europe (0.10, 0.30, and 0.70); North America (0.10, 0.20, and 0.50); South America (0.10, 0.40, and 0.80).