April 8 (UPI) -- Women appear to be at higher risk for chronic pain conditions such as fibromyalgia and certain types of arthritis, and that may be due to genetic differences between the sexes, a study published Thursday by PLOS Genetics found.
In women, 31 genes are associated with chronic pain, and all but one are active in the dorsal root ganglion, a cluster of nerves in the spinal cord that transmit pain signals from the body to the brain, researchers said.
In men, 37 genes are associated with chronic pain, and all of them are active in the dorsal root ganglion, the researchers said.
However, only one of these genes was associated with chronic pain in both sexes, and these subtle differences "could be informative for understanding how chronic pain develops and how to effectively treat chronic pain," study co-author Keira Johnston told UPI in an email.
"Having a more complete understanding of genetic factors related to chronic pain has the potential to improve chronic pain management in the future," said Johnston, a doctoral student at the University of Glasgow in Scotland.
About 50 million adults in the United States experience some form of chronic pain -- 19% of males and 22% of females -- the Centers for Disease Control and Prevention estimates.
Osteoarthritis, rheumatoid arthritis, fibromyalgia and neuralgia, or nerve pain, are among the most common chronic pain conditions nationally, according to the American Chronic Pain Association.
For this study, Johnston and her colleagues looked for genetic variants associated with chronic pain in 209,093 women and 178,556 men, and compared the results.
That the sexes each have 30 or more different genes at the base of the spinal cord involved in chronic pain supports the researchers' previous work, which showed that chronic pain originates to a large extent in the brain and less so at the sites where people may be experiencing pain, they said.
In addition, research into chronic pain could benefit from approaches that take sex into account because it may be a "biological variable" in the development of chronic pain, Johnston and her colleagues said.
"In our study, the genetic differences we saw were quite subtle, but it may be that small differences at the cellular and gene expression level are also involved in differences in male versus female chronic pain development," Johnston said.
"At the gene level distinct genes were associated with chronic pain depending on sex, and there was evidence many were also potentially androgen- and estrogen-regulated," she said, referring to the male and female sex hormones.