Objectives: This study sought to assess differences in perceptions of noxious and non-noxious thermal stimuli applied to the face by: sex and age of the subjects, measures (threshold and suprathreshold), and stimulation site (glabrous (upper lip) and hairy skin (chin). Methods: Medically healthy subjects (Ss, N=178; female=100) judged threshold (Th) and suprathreshold (ST) non-painful (warming (W) and cooling (C)) and painful (P, hot) thermal stimuli delivered to the glabrous (upper lip) and hairy (chin) skin sites of the face in separate sessions. Th was determined by the Method of Limits. Ss rated the ST stimuli using a cross-modality matching (CMM) procedure in which Ss extended a tape measure to rate 7 levels of warming (36°-44°), cooling (30°-18°) and painful (41°-51°) stimuli as well as 5 words that describe the magnitudes of associated sensations. Results: Age was categorized based on a bimodal distribution split at 50 yrs, to yield 92 younger and 86 older adults. Separate ANOVAs were conducted for the following sensory domains: W, C, and P. For all sensory domains lip Th was less than chin (p's< .05). The age effects were moderate to large in magnitude. Older adults had lower Th for all sensory domains (p's<0.01). There was a small, but significant sex difference suggesting that women had higher C Th for chin stimulation (p = .027), accounting for approximately 3% of the variance in ratings.
For all ST sensory domains, there was a significant main effect for stimulus level, showing increased ratings for higher intensity stimulation (p's <0.001). Lip stimulation was perceived as more intense (p's < .01) for all stimuli except C (p < .05). The observed age effects for suprathreshold stimulation in all sensory domains, with younger adults rating stimuli as more intense than older adults (p's < .01) was eliminated when controlling for word rating variability. Women tended to rate W stimulation as more intense than men (p < .05). No other main effects for sex were noted. Conclusion: Older Ss were less sensitive to Th stimuli than younger; but there were no age differences in ST sensations suggesting that the observed Th differences can be explained by more conservative ratings by older Ss.
Supported by P.H.S. DE08845
