We investigated the mortality and disability rate, as well as the healthcare expenditure, for patients with newly diagnosed seropositive rheumatoid arthritis (RA) who were followed-up for up to 10 years, compared to the general population in Korea.
We conducted a nationwide population-based study using a National Health Insurance Service-National Sample Cohort of the Korean population, consisting of 1 million individuals who submitted medical care claims between 2002 and 2013. RA was identified using as the International Classification of Diseases code M05 (seropositive RA), with prescription of any disease-modifying anti-rheumatic drug (DMARD). Our analysis was based on the data of 1655 patients with incident seropositive RA and 8275 non-RA controls. The controls were matched to the RA cohort by sex, age at the time of diagnosis, duration of follow-up, geographic region, type of social security, and household income.
The most commonly used conventional synthetic DMARDs were hydroxychloroquine (71.30%) and methotrexate (69.5%), with adalimumab being the most commonly used biologic DMARD (2.54%). The mortality rate was significantly higher in the RA than the control group (incidence rate ratio [IRR] 1.29, 95% confidence interval [CI] 1.02-1.64) in the first 10 years after diagnosis. Specifically, mortality due to infectious diseases (IRR 4.41, 95% CI 1.60-12.17) and pneumonia (IRR 3.92, 95% CI 1.46-10.53) was significantly higher in the RA than control group. The disability rate was higher in the RA than control group over the first 10 years of the disease (IRR 2.27, 95% CI 1.77-2.92), which was attributed to a higher incidence of physical disability (IRR 3.81, 95% CI 2.81-5.15). Annual health expenditure was greater for the RA than the control group.
Therefore, the rate of mortality and disability, as well as healthcare expenditure, are higher for patients with RA over the first 10 years of the disease onset, than the general population of Korea. The use of claim data has limited the quality of information and there is a limit to the observation period, and we expect the prospective national-wide multicenter cohort for longer period to overcome these limitations.