Gender differences in pain and secondary hyperalgesia after heat/capsaicin sensitization in healthy volunteers.
In most published studies women are more sensitive to experimental pain than men. Enhanced central pain processing in women has been suggested, but psychosocial factors might also have affected the findings. Data from five completed healthy volunteer studies were analyzed to investigate gender differences in development of secondary hyperalgesia. Cutaneous hyperalgesia was induced with the heat/capsaicin sensitization model. Outcome measures were areas of secondary hyperalgesia to brush and von Frey hair stimulation after heat and capsaicin sensitization, rating of pain during heat/capsaicin sensitization, and heat pain detection thresholds. There was a trend toward smaller areas of secondary hyperalgesia in women. After adjusting for estimated gender differences in forearm surface area, areas to brush but not von Frey hair stimulation after capsaicin sensitization were larger in women. Peak pain, but not total pain, during prolonged noxious thermal stimulation was higher in women. There was no gender difference in pain ratings during capsaicin sensitization or in heat pain detection thresholds. The results provided only limited support to the hypothesis that gender differences in clinical pain syndromes can be explained by enhanced central sensitization in women.


CONCLUSIONS
Our findings suggest that gender differences in nociceptive transmission and neuronal sensitization are small and provide only limited support to the hypothesis that gender differences in acute and chronic pain syndromes can be explained by enhanced central sensitization in women.
Jensen
Magnus Thorsten
MT
UCSF Pain Clinical Research Center, Department of Neurology, University of California, San Francisco, San Francisco, California 94115, USA.
Petersen
Karin Lottrup
KL
D000328:Adult; D002211:Capsaicin; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006930:Hyperalgesia / Q000209:etiology / Q000523:psychology*; D008297:Male; D010146:Pain / Q000209:etiology / Q000523:psychology*; D010147:Pain Measurement; D017288:Pain Threshold; D012016:Reference Values; D012737:Sex Factors
D002211:Capsaicin