1.1. Epidemiology

Reporting on epidemiological data for SLE is not coherent among all countries, and the best informative data are obtained from North America and Europe, while less documentation has been received from Africa, Asia, Australia, and South America [1, 6]. Nevertheless, SLE is a global disease in which its incidence, prevalence, time of onset, and mortality are highly influenced by race and ethnicity [6]. For instance, in USA SLE has incidence and prevalence rates that show great variability ranging from 2 to 7.6 per 100,000 per year and 19 to 159 per 100,000 per year, respectively [7, 8]. These variations can originate from differences in ethnicity, race, and age within the studied SLE population and can also stem from differences in the employed diagnostic criteria for SLE. Similar variation trends were also observed in some European countries [9, 10].

One of the important characteristics of SLE is that it predominantly affects women more than men [11] with a disease onset that is influenced by ethnic background. For instance, in a different ethnic background-based study, it was found that the incidence of SLE in African-Caribbean females is higher at younger ages than in Asian or Caucasian females [12]. This agespecific incidence in females of different ethnicities was also seen in other studies performed in different countries [13–15]. However, the reason behind this characteristic SLE predominance in women more than in men is not entirely understood, but it was inferred to be related to hormonal factors. For example, serum prolactin was found at higher levels in SLE patients than a control group, but it is unknown how can prolactin be involved in SLE immune deregulation. Independent of gender, it was reported that generally people of African origin had a higher incidence of SLE than those of European origin [7, 8, 16].

Mortality risk is increased in SLE patients of Chinese, Hispanic, and African backgrounds with strong associations of renal damage [17, 18]. This, however, might relate to the levels of disease awareness and therapeutic adherence that might be different among different populations [6].
