Preliminary evidence suggests that patients with knee osteoarthritis (OA) who have certain alleles of the catechol-O-methyltransferase (COMT) and mu-opioid receptor (OPRM1) genes experience more variability in their day-to-day pain and exacerbation of pain after daily physical activity, compared with patients with other genotypes, according to a study published in Scandinavian Journal of Pain.
Researchers looked at variability in day-to-day knee OA pain among patients with different variants of the COMT and OPRM1 genes. They assigned 120 patients with knee OA to a 22-day assessment protocol in which they wore an accelerometer to measure daily physical activity and completed a pain questionnaire 3 times a day. Multilevel modeling was used to examine the magnitude of within-person variability in pain by genetic group.
Patients with two copies of the Asn40 allele of OPRM1 rs 1799971 showed the greatest variability in day-to-day pain. Patients with the Val/Val genotype of COMT rs4680 showed the greatest pain variability and also experienced the greatest increase in pain as a result of physical activity.