Age confounding: Arthritis prevalence is strongly age-related, and both countries have ageing populations which independently drive numbers upward — making the arthritis correlation harder to isolate than for T2DM or IBD. However, research clearly shows that insulin resistance drives systemic inflammation that accelerates cartilage degradation in osteoarthritis and amplifies autoimmune activity in rheumatoid arthritis, independently of age. Obesity-related osteoarthritis (strongly linked to IR) now accounts for a significant share of new cases in adults under 50.