Research Article: Comorbidity, disability, and healthcare expenditure of ankylosing spondylitis in Korea: A population-based study

Date Published: February 8, 2018

Publisher: Public Library of Science

Author(s): Jeong Seok Lee, Baek-Lok Oh, Hee Young Lee, Yeong Wook Song, Eun Young Lee, Sreeram V. Ramagopalan.


Ankylosing spondylitis (AS) is an inflammatory rheumatic disease typically diagnosed in young age and follows a chronic progressive course. Its impact on the patient is life-long and the burden that AS exerts on society is increasing cumulatively every year. We aimed to quantify the burden of AS and to identify the factors associated with comorbidity, disability, and healthcare expenditure in Korean AS patients.

We conducted a nationwide, population-based study using health insurance data (2003–2013). The analysis included individuals with incident AS (1,111 patients) and controls (5,555 patients) matched by age, sex, income, and geographic region. The incidence rates of extra-articular manifestations (EAMs), comorbidities, mortality, and disability (type and severity) were compared between AS patients and controls. Annual health expenditure per patient was also analyzed. Associations were expressed as odds ratios (ORs) with 95% confidence intervals (95%CIs).

During the follow-up, 28% of AS patients experienced at least one EAM. AS diagnosis was significantly associated with Charlson comorbidity index ≥3 (OR 2.18, 95% CI 1.91–2.48). Disability rate was higher in AS patients than in controls regardless of cause and severity (OR 2.94, 95% CI 2.48–3.48), but crude incidence rate ratios for mortality were not significantly higher. On multivariate analysis, male sex (OR 3.18, 95% CI 2.13–4.75), presence of an EAM (OR 1.63, 95% CI 1.15–2.32), and older age at diagnosis (OR 1.27, 95% CI 1.20–1.35) were evidently associated with increased disability in AS. Presence of an EAM was also associated with increased AS-unrelated expenditures in biologic-naïve patients (median, 1112 vs. 877 USD per person, P < 0.05). In patients with AS, demographic factors and systemic manifestations including EAMs and other comorbidities were associated with increased disability and healthcare expenditures.

Partial Text

Ankylosing spondylitis (AS) is an inflammatory rheumatic disease with musculoskeletal and systemic manifestations [1]. Because AS is typically diagnosed before the age of 40 years and follows a chronic progressive course [2], its impact on the patient is life-long. In addition to the burden on the individual patient, the burden that AS exerts on society is increasing cumulatively every year [3]. This burden is not confined to healthcare costs associated with alleviating back pain and stiffness caused by the disease itself [4–6], but also includes costs associated with managing extra-articular manifestations (EAMs), comorbidities, disability, and mortality, to which AS contributes indirectly [7].

This is the first study to quantitatively assess the burden of AS using representative claim data of the national health insurance service, which covers more than 95% of the Korean population. We found that the disability rate and annual health expenditures were significantly higher in the study group (patients with AS) than in the control cohort (patients without AS, matched with AS patients for sex, age group, income level, and geographic region). We found that the burden of AS was aggravated by clinical features including EAMs, as well as by demographic factors known to be related to AS, such as male sex, old age, and lower income.




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