Impact of Age at Disease Diagnosis on Clinical Manifestations, Disease Activity, and Outcomes in Patients with Systemic Lupus Erythematosus: Single-Center Prospective Cohort Study

Abstract

Background/Purpose: Systemic lupus erythematosus (SLE) is an autoimmune disease that affects frequently in their 20s and 30s. However, SLE could develop in other age group such as childhood-onset or late-onset. We aimed to investigate the influence of age of disease onset on clinical features, disease activity, and outcomes in adult patients with SLE.

Methods: We analyzed 917 adult patients with SLE from 1998 to 2012. The patients were classified into two groups based on the age at disease diagnosis: adult-onset SLE (≥18 and <50 years) and late-onset SLE (≥50 years). The American College of Rheumatology (ACR) criteria for SLE classification, the SLE Disease Activity Index (SLEDAI-2K), adjusted mean SLEDAI-2K (AMS), incidence rate of SLE flares (defined by ≥4 points increase of the SLEDAI-2K compared with that of previous visit), and prescribed medication were compared between two groups. As outcomes, organ damage and mortality were compared using SLICC/ACR Damage Index (SDI) and age- and sex adjusted standardized mortality ratio (SMR), respectively.

Results: Of the 917 SLE patients, 885 (91.4%) patients were adult-onset (mean age 29.4, range 18-49 years) and 32 (3.5%) patients were late-onset (mean age 55, range 50-68 years). After the mean follow-up years of 6.4, the number of cumulative ACR criteria was significantly lower in patients with late-onset compared with adult-onset SLE (4.6±1.2 vs 5.5±1.4, p<0.001). The mean SLEDAI-2K at enrollment (3.3±2.9 vs 5.4±4.2, p<0.001) and adjusted mean SLEDAI-2K over time (2.7±2.1 vs 4.3±2.6, p<0.001) were significantly lower in patients with late-onset compared with adult-onset SLE. The incidence rate ratio of SLE flares (late-onset/adult-onset SLE patients) was 0.44. The use of glucocorticoids and immunosuppressants was similar between two groups, but the use of azathioprine was lower in late-onset SLE patients (9.4% vs 29.8%, p=0.021). The percentage of cumulative SDI≥1 was higher in patients with late-onset compared with adult-onset SLE, but none reached statistical significance (50% vs 43.4%, p=0.576). A total of 42 patients died (6 in late-onset and 36 in adult-onset SLE group). The leading cause of death in both groups was SLE-related diseases, followed by infection. As compared to general population, the age- and sex adjusted SMR in late-onset and adult-onset SLE group was 1.58 (95% CI 0.58-3.43) and 3.34 (95% CI 2.34-4.63), respectively.

Conclusion: Compared with adult-onset SLE, late-onset SLE showed significantly mild clinical features and lower disease activity during follow-up. However, the percentage of patients with organ damage in patients with late-onset SLE was similar to that of adult-onset. The mortality of late-onset SLE was not higher than general population, although the mortality of adult-onset was three times higher than general population. Our results suggest that the clinical prognosis of late-onset SLE is better than adult-onset SLE.