title: Characterizing individual differences in heat-pain sensitivity.
abstract: Heat induced pain has been shown to follow a positively accelerating power function for groups of subjects, yet the extent to which this applies to individual subjects is unknown. Statistical methods were developed for assessing the goodness of fit and reliability of the power function for data from individual subjects with the aim of using such functions for characterizing individual differences in heat-pain sensitivity. 175 subjects rated ascending and random series of contact heat stimuli with visual analogue scales for pain intensity (VAS-I) and unpleasantness (VAS-A). Curve fitting showed excellent model fit. Substitution of model estimates in place of observed VAS scores produced minimal bias in group means, about 0.3 VAS units in the ascending series and 1.0 in the random series, on a 0-100 scale. Individual power function exponents were considerably higher for the ascending than for the random series and somewhat higher for VAS-A than for VAS-I (means: ascending VAS-I=9.04, VAS-A=9.80; random VAS-I=4.95, VAS-A=5.67). The reliability of VAS estimates was high (>==.93), and for the ascending series it remained so when extrapolating 4 degrees C beyond the empirical range. Exponent reliability was high for the ascending series (VAS-I=.92; VAS-A=.91), but considerably lower for the random series (VAS-I=.69; VAS-A=.71). Individual differences constituted 60% of the total variance in pain ratings, whereas stimulus temperature accounted for only 40%. This finding underscores the importance of taking individual differences into account when performing pain studies.
authors.affiliation: Department of Psychology, University of Oslo, PO Box 1094 Blindern, NO-0317 Oslo, Norway Department of Mental Health, Division of Epidemiology, Norwegian Institute of Public Health, PO Box 4404 Nydalen, NO-0403, Oslo, Norway Departments of Oral and Maxillofacial Surgery and Neuroscience, University of Florida, Health Sciences Center, PO Box 100416, Gainesville, FL 32610-0416, USA Department of Clinical Odontology, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo, Norway Department of Anesthesiology, Rikshospitalet University Hospital, NO-0027 Oslo, Norway Department of Genes and Environment, Division of Epidemiology, Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, NO-0403, Oslo, Norway.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Nielsen
authors.forename: Donald D
authors.initials: DD
authors.lastname: Price
authors.forename: Olav
authors.initials: O
authors.lastname: Vassend
authors.forename: Audun
authors.initials: A
authors.lastname: Stubhaug
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Harris
mesh_terms: D000328:Adult; D003198:Computer Simulation; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008954:Models, Biological; D010146:Pain / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013696:Temperature; D014427:Twins