Effects of ageing on spinal motor and autonomic pain responses.

The course of ageing leads to various changes in the nervous system, which can affect pain processing in the elderly. However, the affection of different components of the nociceptive system remains unclear. To investigate basic nocifensive responses, we compared age-related changes of autonomic and motor reflex responses to noxious electrical stimulation. In 39 healthy young subjects (mean +/- S.D.; 24.1 +/- 3.3 years) and 52 healthy elderly subjects (mean +/- S.D.; 71.9 +/- 5.3 years) the nociceptive flexion reflex (NFR) and the sympathetic skin response (SSR) were determined using noxious electrical stimulation of the sural nerve. Verbal pain ratings were assessed in addition. No ageing effects on the NFR and on verbal pain ratings were found, whereas the SSR amplitude declined significantly with ageing. Since both SSR and NFR share comparable primary afferent pathways and the motor as well as the subjective responses to noxious stimulation were preserved, our data seem to suggest that central or peripheral efferent sympathetic functions are altered by age.