Incidence OF systemic sclerosis in allegheny county, Pennsylvania. A twenty‐year study of hospital‐diagnosed cases, 1963–1982

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Abstract
Objective. To determine the incidence of hospital‐diagnosed systemic sclerosis (SSc) among residents of Pittsburgh and Allegheny County, PA, from 1963 through 1982.Methods. Medical records from all Allegheny County hospitals were searched using International Classification of Diseases codes for patients diagnosed with SSc. Each case was reviewed and verified by a physician, according to specified criteria. Age‐adjusted incidence rates were computed for race and sex, and results were expressed as new cases per million population per year, with the 1970 Allegheny County population serving as the standard.Results. Four hundred forty‐four cases of SSc were identified during this 20‐year survey, for a total annual incidence of 13.9 per million population. Overall, the incidence rate doubled during 1973–1982 compared with the first time interval of the study, with the greatest increase occurring in women. Among the younger population (ages 15–24), black women had the highest incidence of SSc (21.2 per million population). Overall, the female‐to‐male incidence ratio was 3:1, and was slightly higher (3.4:1) during the childbearing years (ages 15–44). Men under age 35 and children infrequently developed SSc.Conclusion. The incidence of SSc reported in this study increased with time. Although this trend was most likely due to improved detection and medical record techniques, the incidence rate stability in men compared with women suggests that there may have been a true increase in the incidence of SSc in this population, particularly in women.