Cluster analysis of multiple experimental pain modalities

• Published in: Pain (Amsterdam) Vol. 116; no. 3; pp. 227 - 237
• Main Authors: Hastie, Barbara A., Riley, Joseph L., Robinson, Michael E., Glover, Toni, Campbell, Claudia M., Staud, Roland, Fillingim, Roger B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2005; Lippincott Williams & Wilkins, Inc; Elsevier
• Subjects: Adolescent; Adult; Analysis of Variance; Biological and medical sciences; Cluster Analysis; Demography; Experimental pain; Factor analysis; Female; Fundamental and applied biological sciences. Psychology; Hot Temperature - adverse effects; Humans; Illness and personality; Illness, stress and coping; Individuality; Ischemia - complications; Male; Pain - classification; Pain - etiology; Pain - physiopathology; Pain - psychology; Pain Measurement - methods; Pain threshold; Pain Threshold - physiology; Pressure - adverse effects; Principal Component Analysis - methods; Psychological Tests; Psychology and medicine; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Psychophysics; Sex Factors; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Summation; Surveys and Questionnaires; Temporal; Vertebrates: nervous system and sense organs; Cluster analysis; Factor analysis; Temporal; Pain threshold; Experimental pain; Psychophysics; Summation; Pain sensitivity; Temporal summation; Sex; Cluster; Psychosocial factor; Pain
• ISSN: 0304-3959; 1872-6623
• DOI: 10.1016/j.pain.2005.04.016

Identifying individual differences in pain is an important topic; however, little is known regarding patterns of responses across various experimental pain modalities. This study evaluated subgroups emerging from multiple experimental pain measures. One hundred and eighty-eight individuals (59.0% female) completed several psychological instruments and underwent ischemic, pressure, and thermal pain assessments. Thirteen separate pain measures were obtained by using three experimental pain modalities with several parameters tested within each modality. The pain ratings and scores were submitted to factor analysis that identified four pain factors from which Pain Sensitivity Index (PSI) scores were computed: heat pain (HP), pressure pain (PP), ischemic pain (IP), and temporal summation of heat pain (TS). Cluster analyses of PSI scores revealed four distinct clusters. The first cluster demonstrated high overall pain sensitivity, the second cluster revealed high TS, the third cluster showed particular insensitivity to IP and low sensitivity across pain modalities except PP, and the fourth cluster demonstrated low sensitivity to PP. Significant correlations were found between psychological measures and Index scores and those differed by sex. Cluster membership was associated with demographic variables of ethnicity and sex as well as specific psychosocial variables, although cluster differences were only partially explained by such factors. These analyses revealed that groups respond differently across varied pain stimuli, and this was not related solely to demographic or psychosocial factors. These findings highlight the need for future investigation to identify patterns of responses across different pain modalities in order to more accurately characterize individual differences in responses to experimental pain.