Damage accumulation in systemic lupus erythematosus and its relation to disease activity and mortality

Abstract

Objective: To describe damage accrual and the interconnections between disease activity measures, damage accrual, and death in a Nordic lupus cohort.

Methods: Longitudinal study in the population-based Tromso lupus cohort. Disease activity [SLE Disease Activity Index (SLEDAI)] and disease damage [by Systemic Lupus International Collaborating Clinics (SLICC)/American College of Rheumatology (ACR) Damage Index (SDI)] were recorded for each visit. Weighted average SLEDAI scores (WAS) were calculated to correct for variable observation times. Development of damage (SDI > 0), severe damage (SDI >or= 3), and death were used as separate endpoints. Univariate nonparametric analysis identified and hazard ratios (HR) by Cox regression techniques confirmed the independence of predictors for each outcome.

Results: Through 11.9 years of followup, 72 patients (46%) remained free of damage, 51 (32%) developed moderate damage, and 35 (22%) developed severe damage. SDI scores were higher in 37 nonsurvivors (23.4%; SDI 2.1) than in survivors (SDI 0.9; p < 0.05). Damage accrual was linear throughout the first decade of disease. The only independent predictor for SDI >/= 3 was a WAS score > 3 (hazard ratio 2.34; 95% CI 1.1-4.9). Age > 40 years at diagnosis (HR 5.6, 95% CI 2.4-12.7) and WAS > 3 (HR 2.4, 95% CI 1.2-4.9) were significant predictors for death.

Conclusion: Damage accrual in SLE occurred in 54% of patients in a linear fashion over the first decade of disease. Global disease activity was the main determinant of damage accrual. Accrued damage was not an independent risk factor for death, which was predicted by age > 40 years and WAS > 3.