Systemic lupus erythematosus
The rate of SLE varies between countries, ethnicity, and sex, and changes over time. In the United States, one estimate of the rate of SLE is 53 per 100,000; other estimates range from 322,000 to over 1 million. In Northern Europe the rate is about 40 per 100,000 people. SLE occurs more frequently and with greater severity among those of non-European descent. That rate has been found to be as high as 159 per 100,000 among those of Afro-Caribbean descent. Childhood-onset systemic lupus erythematosus generally presents between the ages of 3 and 15 and is four times more common in girls.
Sjögren syndrome
SS is the second most common rheumatic autoimmune disorder, behind rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). There are no geographical differences in the rates of SS. SS has been reported in all areas of the world, although regional rates have not been well studied. Depending on the criteria for determining prevalence, studies estimate the prevalence of SS at 500,000 to 2 million people in the United States. Moreover, other broader studies of prevalence of SS range widely with some reports of up to a prevalence of 3% of the population. A few studies that have been conducted on the incidence of SS report that the incidence of the syndrome varies between 3 and 6 per 100,000 per year.