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.
aUniversity of Florida College of Dentistry, Division of Public Health Services and Research, 1600 SW Archer Road, HSC D8-37, P.O. Box 100404, 32610-0404 Gainesville, FL, USA
bMalcom Randall VA Medical Center, Gainesville, FL, USA
cDepartment of Clinical and Health Psychology, University of Florida, Gainesville, FL, USA
dDepartment of Medicine, University of Florida, Gainesville, FL, USA
*Corresponding author. Tel.: +1 352 392 9369; fax: +1 352 392 2672.
Received 15 September 2004; received in revised form 5 April 2005; accepted 18 April 2005.