The incidence of postural orthostatic tachycardia syndrome in the population of Zagreb, Croatia.

Aim: To estimate the incidence of postural orthostatic tachycardia syndrome (POTS) in the population of Zagreb, Croatia, and to determine the patients' demographic and clinical characteristics.

Methods: From 2012-2017, we identified patients with POTS by a retrospective analysis of medical records at University Hospital Center Zagreb. Crude incidence rates were directly standardized by age according to the European and World Standard Population.

Results: Out of 385 patients with suspected POTS, 23 had a definitive POTS diagnosis. The annual incidence ranged from 3.3 to 14.8 per 1000000 for both sexes combined. The highest incidence rates were in the age groups 18-29 and 30-39 years, with female predominance. The mean age at diagnosis was 30.7 years (standard deviation ±9.2, range 18-52). The median duration of symptoms at diagnosis was 7.5 months (range 3-180 months). Regarding associated comorbidities, two patients had chronic gastritis and one patient had each of the following: epilepsy, prior subarachnoid hemorrhage, anxiety, mitral insufficiency, obstructive sleep apnea, hypothyreosis, and irritable bowel syndrome. In patients not fulfilling the criteria for POTS, the most common alternative diagnoses were autonomic dysfunction due to multiple sclerosis in 22, anxiety disorder in 17, epilepsy in 16, and orthostatic tachycardia due to deconditioning in 13 patients.

Conclusion: The data obtained in this study can be used to optimize disease surveillance in population, comprehensive assessment of disease burden, and organization of health care services.