Epidemiology
Although acquired torticollis is one of the most common forms of dystonia, it remains a rare disorder. Prevalence has been estimated at 1 in 10,000 to 20,000 people in the general population.[1] Incidence and prevalence are likely to be under-estimated in studies because of under-recognition of the condition.
In a retrospective study of a large health maintenance organisation population in California, US from 1997 to 1999, 66 confirmed incident cases were identified in 8.6 million person-years of observation, leading to a minimum incidence of 0.8 per 100,000 person-years among people aged 30 years and older.[2] This study also found:
Incidence was 2.5 times higher among women than men
Mean age at diagnosis was 56 years among women and 45 years among men
Patients had symptoms for an average of 4 to 5 years prior to confirmed diagnosis
A disproportionate number of cases occurred among patients of white ancestry.
A study of the same population from 2003 to 2007 identified 200 incident cases, equivalent to an incidence of 1.18/100,000 person-years from 2003 to 2007.[3]
A population-based study in Italy found 44.8 cases per 1 million persons. This may be a low estimate, as this was based upon diagnoses reported in the healthcare system.[4]
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