Context Primary aldosteronism (PA) is the most common cause of secondary hypertension. Yet, the incidence of PA in the general population has not been studied. Objective To estimate the incidence of PA in the general population. Design and methods Patients who had received a diagnostic code for PA between 1987 and 2016 were identified in the Swedish National Patient Registry. Assessment of clinical and biochemical data was used to validate the diagnosis. The annual incidence of PA was calculated by using the number of inhabitants in the Västra Götaland County as reference. Results Of 570 identified patients, 473 (83 %) had confirmed PA. Eligible for the incidence analysis were 416 patients, 248 (60%) men and 168 (40%) women, diagnosed with PA between 1987-2016. The mean (±standard deviation) age at diagnosis was 56±12 years. The median (interquartile range) annual incidence was 2 (1-2) cases per million between 1987 and 1996, 6 (4-9) cases per million between 1997 and 2006 and 17 (12-24) cases per million between 2007 and 2016. At the end of the study (December 31 st 2016), 386 patients with confirmed PA were alive and living in the Västra Götaland County, giving a prevalence of 231 cases per million (0.022%). Conclusions Despite increasing incidence, the proportion of patients identified with PA is lower than expected. Given the serious consequences of untreated PA, the noticeably low prevalence at the end of the study stresses the need to increase the awareness of PA among health care providers.

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