15 October 2006

Age differences in endogenous analgesia

Age-related differences in the endogenous analgesic response to repeated cold water immersion in human volunteers
Washington, et al.
Recent animal studies using stress-induced analgesia have suggested a general age-related decline in endogenous pain inhibitory systems.
The aim of the current study was to examine age-related differences in the magnitude of endogenous analgesia in human volunteers, using
psychophysical measures of neuroselective electrical, and thermal CO2 laser induced pain thresholds, before, immediately after and 1 h after
repeated cold water immersion of the hand. Sensory detection thresholds did not differ between age groups indicating that the functional
integrity of primary afferent sensory ®bres appears to be intact in older people. Consistent with many previous studies, older adults required a
higher intensity of noxious stimulation in order to ®rst report the presence of pain. The cold water immersion task was effective in eliciting a
powerful analgesic response, regardless of age; pain thresholds were shown to increase by up to 100% immediately after the cold pressor test.
This effect was relatively transient with thresholds returning to baseline within 1 h. The magnitude of analgesic response, however, was found
to be signi®cantly less in older people. Age differences in the ef®cacy of endogenous analgesic systems may be expected to reduce the ability
of older adults to cope with severe persistent pain states and may help explain some of the variation in the literature on pain report.
(c) 2000 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved.
Pain 89 (2000) 89-96
PII: S0304-3959(00)00352-3
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