Implication of local skin blood flow in pain tolerance in the elderly

Background and aims: A decrease in pain tolerance is observed in aging, especially when tested with prolonged warm nociceptive stimuli. This type of stimuli implies a response of the cutaneous vasomotor system to ensure local thermal regulation. However, in the elderly, alterations in cutaneous vasodilation in response to local warming have been observed. We can therefore hypothesize that an alteration in local skin blood flow may participate in the decrease of pain tolerance with age. Methods: 20 young and 20 old participants performed a pain resistance test. They were asked to place their hand in an airtight box with the air temperature regulated at 65°C and hold it until the pain became unbearable. The maximum duration of the test was 15 minutes. We continuously measured the skin temperature and local blood flow of the hand in the box. Participants were also asked to continuously estimate pain intensity using a visual analog scale. Results: The results showed that the elderly have a decreased blood flow compared to the young. We also observed that pain tolerance is impaired in the elderly as 85% of the young subjects resisted pain until the end of the test, while this proportion is 50% in the elderly. In the elderly who did not resist until the end of the test, the results showed that blood flow correlated with pain judgment, whereas no correlation was observed in the other participants. Conclusions: Our results suggest that altered local skin blood flow may influence thermal pain tolerance in aging