Ethnicity-specific patterns of epigenetic age acceleration in rheumatoid arthritis

Rheumatoid arthritis (RA) is an age-related chronic inflammatory disease which may include accelerated biological ageing processes in its pathogenesis. To determine if increased biological age is associated with risk of RA and/or is present once disease is established. We used DNA methylation to compare biological age (epigenetic age) of immune cells in adults at risk of RA and those with confirmed RA, including twins discordant for RA. The established RA studies were secondary analyses of existing DNA methylation data. Sub-group analysis considered the influence of ethnicity. Four epigenetic clocks were used to determine DNA methylation age. DNA methylation age was no different in adults at risk of RA in the Leiden Clinically Suspect Arthralgia (CSA) cohort (n = 38 developed RA, n = 24 did not), and there was also no difference in DNA methylation age between 77 UK twins discordant for RA, or adults with established RA from the Swedish EIRA cohort (n = 342) compared to healthy controls (n = 328). A sub-group analysis of RA patients of South Asian ethnicity (10 RA patients, 14 healthy controls) showed DNA methylation age acceleration of 3.3 years (p = 0.00014) using the mean DNA methylation age of four epigenetic clocks. Our study suggests that epigenetic age acceleration may be differentially influenced by South Asian ethnicity, but that RA was not generally associated with accelerated epigenetic age. The higher epigenetic age in the South Asian patients may explain the earlier age of onset in this minority ethnic population.