A recent study has found that women may be at greater risk of experiencing chronic pain because of the genetic differences between men and women.
Chronic pain is defined as pain persisting longer then 3 months. It can be a primary or secondary disorder associated with injury, surgery or a range of medical conditions. Chronic pain is highly prevalent worldwide and poses a huge socioeconomic and public health burden. The mechanisms and factors underlying susceptibility and development of chronic pain is not fully understood. Heritability figures from twin, pedigree and factor analysis studies range from 30 to 46%. Alternatively, SNP heritability from GWAS is found to be between 7 and 10%.
It is increasingly recognised that sex differences in many complex human traits are important. Sex has a wide range of effects on the function of the genome and subsequent phenotypes. The effects can be mediated by sex-differential gene expression, sex differences in methylation and eQTL effects or via differing levels and actions of hormones. Chronic pain is more common in women than in men, suggesting that sex plays a role in susceptibility to this condition.
In this study, published in PLOS Genetics, researchers explored this disparity by undertaking the largest ever genetic study of chronic pain with sex-stratified analyses. They specifically explored multisite chronic pain (a derived chronic pain phenotype) in the UK Biobank. The data consisted of 178,556 men and 209,093 women. In women, 31 genes were associated with chronic pain, whereas 37 genes were linked to pain in men. A single gene, DCC, was associated with chronic pain in both sexes.
The team also investigated whether the activity of these genes was altered in tissues known to be related to chronic pain. They found that all 37 genes in men and 30 of the genes in women were active in the dorsal root ganglion. These are a cluster of nerves in the spinal cord that transmit pain signals to the brain.
Overall, their findings indicate that sex differences in chronic pain exist at the SNP, gene and transcript abundance levels. Moreover, the results support the idea that chronic pain originates to a large extent in the brain in both sexes.
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