Incidence and prevalence of systemic sclerosis: a systematic literature review

To determine the incidence and prevalence of systemic sclerosis (SSc) in adults, its epidemiological tendencies over time, and its possible key determinants.

We performed a systematic literature review using the keywords "systemic sclerosis," "incidence," "prevalence," and "epidemiology."

We found 32 articles published from 1969 to 2006 in which the prevalence of SSc ranged from 7/million to 489/million and its incidence from 0.6/million/y to 122/million/y. There were many geographical variations: SSc prevalence was higher in the USA (276/million in 1990) and Australia (233/million in 1999) than in Japan and Europe, where a north-south gradient was also observed (France: 158/million in 2001 and England: 88/million in 2000). In some regions (Ontario, Rome, near London's airports) there was an unusually high number of SSc cases (3, 5, or 1000 times greater than expected), suggesting spatiotemporal clustering, although no key determinants could be identified. Furthermore, there seemed to be a trend toward an increase in the incidence of SSc over time, but this tendency is uncertain due to lack of uniformity in study methods and designs. We also found that susceptibility to the disease differed according to sex, age, and race.

Uniform clinico-epidemiological studies with standard diagnostic and classification criteria are needed to refine the epidemiological features of SSc. Homogeneous study methods with exhaustive case ascertainment as seen in a "capture-recapture" analysis will also be necessary to obtain reliable data.