Background: Palindromic rheumatism (PR), is a clinical syndrome characterized by the intermittent acute arthritis or peri-arthritis involving one or several regions. It presents with pain with or without redness or swelling, lasting from a few hours to days with variable symptom-free periods. Different from rheumatoid arthritis (RA), PR does not lead to residual joint destruction. A recent study showed that RA patients had a mean loss of life expectancy of about 5 years [1]. However, whether all-cause mortality rate in PR patients differs from that in individuals without PR was still known.

Objectives: To compare the all-cause mortality rate between PR patients and non-PR individuals.

Methods: Usint a two-million representative cohort from the 2000-2018 Taiwan‘s National Health Insurance Research Database, we identified 2,791 incident adult (aged ≥ 20 years) PR patients. Matching for sex, age and year of index date at a 1:40 ratio, we selected 111,640 non-PR individuals for comparison. Then using the greedy algorithm, we further selected another comparison group of 5,582 non-PR individuals by propensity score (PS) matching for Charson comorbidity index (CCI) at a 1:2 ratio. Using the Cox proportional hazard model, we examined the risk of all-cause mortality in PR patients shown as adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs). Potential confounders included age, sex, CCI, a history of immune mediated inflammatory disease (IMID) including systemic lupus erythematosus erythematosus (SLE), RA, idiopathic inflammatory myopathies (IIM, including dermatomyositis and polymyositis), Sjögren’s syndrome (SS), inflammatory bowel disease (IBD), psoriasis, and medication use including corticosteroid (0, 1-5, >5 mg/day prednisolone equivalent dose), methotrexate, sulfasalazine, leflunomide, hydroxychloroquine and nonsteroidal anti-inflammatory drugs within one year before the index date.

Results: In the 1:2 PS-matched popultion, the mean age was 48.4 years and female to male ratio was 1.54 in the PR group and non-PR group. Amon 2,791 PR patients, 226 (8.10%) died during a mean follow-up period of 8.29 years; while 11,958 (10.71%) of 111,640 non-PR individuals expired during a mean follow-up period of 8.13 years. The all-cause mortality rates in PR patients and non-PR individuals were 976.83 per 10 ⁵ years and 1,317.93 per 10 ⁵ years, respectively (incidence rate ratio, 0.74; 95% CI, 0.65-0.85, p < 0.001). After adjusting for potential confounders, the risk of all-cause mortality was significantly lower in PR patients compared with non-PR individuals (aHR, 0.70; 95% CI, 0.59–0.82). In the subgroup of subjects without IMID, the relative risk of all-cause mortality in PR patients compared with non-PR individuals was 0.68 (0.58–0.80), p < 0.001. In the subgroup of subjects with a history of any IMID, the relative mortality risk in PR patients compared with the non-PR group was 0.64 (0.30–1.34), p = 0.236. The top 3 causes of mortality with their proportions in the PR group (n = 226) were neoplasms (28.3%), diseases of circulatory system (23.5%) and diseases of the respiratory system (11.5%). While the top 3 causes of mortality in the non-PR group (n = 11,958) was neoplasms (32.3%), diseases of circulatory system (21.5%) and disease of respiratory system (9.6%).

Conclusion: This population-based cohort study showed that the all-cause mortaltiy rate in PR patients was lower than that in non-PR individuals, in particular in subjects without a history of IMIDs.

REFERENCES:

[1]Chiu YM, et al. Arthritis Rheumatol 2021 May;73(5):750-758

Disclosure of Interests: None declared