Melatonin is a potential novel analgesic agent for osteoarthritis: Evidence from cohort studies in humans and preclinical research in rats.

Melatonin exhibits potential for pain relief and long-term safety profile. We examined the analgesic effects of oral melatonin on osteoarthritis (OA) and investigated the underlying mechanism. Using data from a UK primary care database, we conducted a cohort study in individuals with OA to compare the number of oral analgesic prescriptions and the risk of knee/hip replacement between melatonin initiators and hypnotic benzodiazepines (i.e., active comparator) initiators using quantile regression models and Cox-proportional hazard models, respectively. To elucidate causation, we examined the effects of melatonin on pain behaviors and explored several metabolites that may serve as potential regulatory agents of melatonin in the monoiodoacetate rat model of OA. Using data from another community-based cohort study, that is, the Xiangya OA Study, we verified the association between the key serum metabolite and incident symptomatic knee OA. Compared with the hypnotic benzodiazepines cohort (n = 8135), the melatonin cohort (n = 813) had significantly fewer subsequent prescriptions of oral analgesics (50th percentile: 5 vs. 7, 75th percentile: 19 vs. 29, and 99th percentile: 140 vs. 162) and experienced a lower risk of knee/hip replacement (hazard ratio = 0.47, 95% Cl: 0.30-0.73) during the follow-up period. In rats, oral melatonin alleviated pain behaviors and increased serum levels of glycine. There was an inverse association between baseline serum glycine levels and the risk of incident symptomatic knee OA in humans (n = 760). In conclusion, our findings indicate that oral melatonin shows significant potential to be a novel treatment for OA pain. The potential role of glycine in its analgesic mechanism warrants further investigation.

Risk of COVID-19 among unvaccinated and vaccinated patients with systemic lupus erythematosus: a general population study.

OBJECTIVE: To compare the risk of SARS-CoV-2 infection and its related severe sequelae between patients with systemic lupus erythematosus (SLE) and the general population according to COVID-19 vaccination status. METHODS: We performed cohort studies using data from The Health Improvement Network to compare the risks of SARS-CoV-2 infection and severe sequelae between patients with SLE and the general population. Individuals aged 18-90 years with no previously documented SARS-CoV-2 infection were included. We estimated the incidence rates and HRs of SARS-CoV-2 infection and severe sequelae between patients with SLE and the general population according to COVID-19 vaccination status using exposure score overlap weighted Cox proportional hazards model. RESULTS: We identified 3245 patients with SLE and 1 755 034 non-SLE individuals from the unvaccinated cohort. The rates of SARS-CoV-2 infection, COVID-19 hospitalisation, COVID-19 death and combined severe outcomes per 1000 person-months were 10.95, 3.21, 1.16 and 3.86 among patients with SLE, and 8.50, 1.77, 0.53 and 2.18 among general population, respectively. The corresponding adjusted HRs were 1.28 (95% CI: 1.03 to 1.59), 1.82 (95% CI: 1.21 to 2.74), 2.16 (95% CI: 1.00 to 4.79) and 1.78 (95% CI: 1.21 to 2.61). However, no statistically significant differences were observed between vaccinated patients with SLE and vaccinated general population over 9 months of follow-up. CONCLUSION: While unvaccinated patients with SLE were at higher risk of SARS-CoV-2 infection and its severe sequelae than the general population, no such difference was observed among vaccinated population. The findings indicate that COVID-19 vaccination provides an adequate protection to most patients with SLE from COVID-19 breakthrough infection and its severe sequelae.