Is Adult-Onset Dystonia a Rare Disease? Time for Population-Based Studies

Adult-onset dystonia1is considered a rare disease, aconclusion based on the relatively homogeneous lowprevalence estimates provided by the majority of studiesconducted between 1980 and 2011. Among the 19 stud-ies performed in this period,2-2015 service-based/recordlinkage system studies and 3 population studies yieldedcrudeprevalenceestimates ranging between 3.0 and43.0 × 105, with estimates from most studies (10 of 18)narrowly ranging from 10.1 to 14.4 × 105.3-6,8,10,11,13,14Only one population-based study in Northern Italy19yielded a signican tly higher estimate, 732 × 105in peo-ple a ged 50 years or older, but interpretation of thisstudy was limited by methodological issues (see later