Objective: Although Cushing's disease is a well documented clinical entity, there is no epidemiological information about it. The present study tries to obtain this information.
Design and patients: Forty-nine patients affected by Cushing's disease living in Vizcaya (Spain) between 1975 and 1992 were considered for an epidemiological study.
Results: The prevalence of known cases at the end of 1992 was 39.1 per million inhabitants. The average incidence of newly diagnosed cases was 2.4 cases per million people per year. Cushing's disease was more frequent in women (n = 46) than in men (n = 3), with a ratio of 15:1. Diabetes mellitus and hypertension were observed in 38.7 and 55.1% of patients, respectively. Remission of Cushing's disease was achieved in 36 out of 41 patients (87.5%). In general, the mortality was higher than that expected for the control population (standardized mortality ratio, SMR 3.8, 95% confidence interval, CI 2.5-17.9, P < 0.03). Concerning the cause of death, the SMR of vascular disease was 5 (95% CI 3.4-48.6, P < 0.05). Higher age, persistence of hypertension and abnormalities of glucose metabolism after treatment, were independent predictors of mortality (multivariate analyses, P < 0.01).
Conclusions: Prevalence of Cushing's disease was 39.1 cases/million inhabitants and average incidence was 2.4 cases/million per year. Mortality was elevated, due to vascular disease, associated with higher age, persistence of hypertension and impaired glucose metabolism.