Aging and right-left asymmetry in experimental pain measurement.

Verbal psychophysical measurements were performed on 100 subjects, both male and female, aged from 20 to 82 years, to ascertain whether different responses to pain exist between the right and left sides of the body in relation to aging and to different capacities of the cerebral hemispheres to process emotions. A single-phase step current applied to the forearm provided a standard noxious stimulus. Sensory threshold (S), pain threshold (P), and tolerance threshold (T) were measured. The sample set was divided into 2 comparable groups either older or younger than 60 years of age. A common trend was found in both groups: right-side scores were consistently lower than the homologous left-side scores. This difference was significant for all thresholds in elderly subjects but only for the pain threshold in the younger subject group. Two-way ANOVA test of the two group scores did not reveal differences due to sex, but age was an influencing factor for sensory and pain thresholds, higher scores being found in the older subject group. An interpretation of the results embodies hemispheric capacities to process verbal and emotional stimuli.