Inverse association between metabolic dysfunction-associated steatotic liver disease and incident rheumatoid...

Chronic hepatitis B (CHB) frequently coexists with metabolic dysfunction-associated steatotic liver disease (MASLD). This study aimed to determine whether MASLD is a risk factor for incident rheumatoid arthritis among middle-aged patients with CHB in a real-world setting.

A population-based cohort study was conducted using the Korean National Health Insurance Service, including 114,425 middle-aged CHB individuals (aged 40-65 years) classified as having either MASLD or non-SLD. Cox proportional hazards regression and Fine-Gray subdistribution hazard models were applied to assess RA risk, accounting for all-cause mortality as a competing event. All patients were followed up until RA, death, or January 31, 2022.

During 792,777 person-years of follow-up, 867 incident RA cases were identified. CHB patients with MASLD had a significantly lower risk of RA development compared to non-SLD participants (subdistribution hazard ratio [SHR], 0.82; 95% CI, 0.69-0.97). This effect was more obvious among younger aged patients (< 50 years). Additionally, higher daily alcohol consumption (1 g/day) was associated with an increased adjusted SHR for RA among all middle-aged CHB patients (1.007; 95% CI, 1.003-1.012).

In middle-aged patients with CHB, the presence of MASLD was associated with a lower risk of developing RA. However, the underlying mechanisms remain unclear, and residual confounding by CHB severity, liver disease stage, or antiviral treatment may have contributed to the observed association. Further studies are warranted to clarify these potential mechanisms linking CHB, MASLD, and RA risk. Key Points • In a nationwide Korean cohort of 114,425 middle-aged adults with CHB, MASLD was associated with a lower incidence of seropositive rheumatoid arthritis compared with non-steatotic liver disease. • In patients with CHB, MASLD may represent a distinct clinical state whose meaning could differ from standalone MASLD because it may be intertwined with the CHB disease stage and immune milieu.