Late-onset primary dystonia in Zhejiang province of China: a service-based epidemiological study.

Dystonia is characterized by sustained muscle contractions, causing repetitive movements and abnormal postures. The epidemiological study of dystonia of Chinese population was limited reported. In this study, we investigated the epidemiology of primary dystonia, and its clinical characteristics in an adult population in China. We identified all dystonia patients from the movement disorders database and botulinum toxin clinic between 2009 and 2013. The medical records were reviewed to verify the diagnosis of dystonia, and demographic and clinical data were collected. A total of 1481 patients with primary dystonia were studied. The most common focal dystonia were blepharospasm (56.4 %), cervical dystonia (36.7 %), limb dystonia (3.4 %), oromandibular dystonia (2.9 %) and laryngeal dystonia (0.6 %). Males with primary dystonia were found to have an earlier age of onset. A female predominance was noted for most of the primary dystonia, with a men to women ratio (M:F) of 1:2.01. The minimum estimate of prevalence of primary dystonia was 27.0 (95 % confidence interval: 25.6-28.3) per million persons in this study. Despite the difference in genetic background and geographic area, the epidemiological features of dystonia in China from our study share most features around the world, such as women dystonia dominance, early-onset age of dystonia with women, etc. But East Asia countries (China and Japan) may share more common features of dystonia.