Purpose To determine the association between the number of flares systemic lupus erythematosus (SLE) patients experience and damage accrual, independently of other known risk factors.

Methods SLE patients (34 centres, nine Latin American countries) with a recent diagnosis (≤2 years) and ≥3 evaluations were studied. Disease activity was ascertained with the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and damage with the SLICC/ACR Damage Index (SDI). Flare was defined as an increase ≥4 points in the SLEDAI between two study visits. An ambidirectional case- crossover design was used to determine the association between the number of flares and damage accrual.

Results 901 patients were eligible for the study; 500 of them (55.5%) experienced at least one flare, being the mean number of flares 0.9 (SD: 1.0). 574 intervals from 251 patients were included in the case-crossover design since they have case and control intervals, whereas, the remaining patients did not. Their mean age at diagnosis was 27.9 years (SD: 11.1), 213 (84.9%) were women. The mean baseline SDI and SLEDAI were 1.3 (1.3) and 13.6 (8.1), respectively. Other features were comparable to those of the entire sample. After adjusting for possible confounding variables, the number of flares, regardless of their severity, was associated with damage accrual (SDI) OR 2.05, 95% CI 1.43 to 2.94, p<0.001 (OR 2.62, 95% CI 1.31 to 5.24, p=0.006 for severe and OR 1.91, 95% CI 1.28 to 2.83, p=0.001for mild-moderate).

Conclusions The number of flares patients experience, regardless of their severity, increases the risk of damage accrual, independently of other known risk factors.