Systemic lupus erythematosus in northwestern Spain: a 20-year epidemiologic study

Abstract

To further investigate the epidemiology of systemic lupus erythematosus (SLE) in southern Europe, we assessed the incidence, prevalence, clinical spectrum of the disease, flares, and survival of patients diagnosed with SLE in the Lugo region of northwestern Spain. Between January 1987 and December 2006, 150 Lugo residents were diagnosed as having SLE according to the 1982 American College of Rheumatology criteria for the classification of SLE. Women outnumbered men (127 [84.7%] vs. 23 [15.3%]). The mean age at the time of disease diagnosis was 46.1 ± 19.6 years. The mean follow-up from the time of disease diagnosis was 7.8 ± 4.5 years. The age- and sex-adjusted annual incidence rate over the 20-year study period was 3.6 (95% confidence interval [CI], 3.0-4.2) per 100,000 population aged 15 years and older. The overall annual incidence rate over the 20-year study period in women (5.9/100,000 population aged ≥15 yr; 95% CI, 4.9-7.0) was higher than in men (1.1/100,000 population aged ≥15 yr; 95% CI, 0.7-1.7) (p < 0.001). By December 31, 2006, the overall age-adjusted SLE prevalence in the Lugo region for patients who fulfilled at least 4 of 1982 American College of Rheumatology criteria was 17.5 per 100,000 population aged 15 years and older (95% CI, 12.6-24.1). Prevalence in women (29.2/100,000 population aged ≥15 yr; 95% CI, 20.0-40.7) was higher than in men (5.8/100,000 population aged ≥15 yr; 95% CI, 2.0-12.0).

The most frequent clinical manifestation was arthritis. As reported in population-based studies on SLE patients of European descent, renal disease was observed in only 27.3% of the patients. The rate of flares was 0.084/year. A younger age and the presence of nephritis at the time of disease diagnosis were associated with the development of flares during the follow-up of Lugo patients. Compared with the general population the probability of survival in patients with SLE was significantly reduced (p = 0.04).

In conclusion, the present study establishes a baseline estimate of the incidence and clinical spectrum of SLE in northwestern Spain. According to our results, the incidence of SLE in northwestern Spain is slightly higher than that reported in most European regions. Patients with SLE from northwestern Spain have a later average age onset and a lower frequency of nephritis than in the African-American population. However, our data show a reduced probability of survival in Spanish patients with SLE.