Epidemiology

AA is a common disorder with an estimated prevalence of 1 in 1000 people and a worldwide lifetime incidence of around 2%, which is similar to that reported in the US population.[2][4][5] The study showed that it affects both sexes equally and is seen in all age groups with no known ethnic predominance. Incidence is higher in children and young adults.[6]

A hospital-based study in Greece found that a higher prevalence of AA occurred between the ages of 21 and 50 years than in other age groups. There was also a slightly higher prevalence in males than in females.[7]

Patients usually present with several episodes of hair loss and hair regrowth during their lifetime. The course is irregular and unpredictable. The recovery from hair loss may be complete, partial, or none. The incidence of the severe chronic form of the condition is 7% to 10% in affected people.[8] Indicators of a poor prognosis are the presence of other immune diseases, family history, young age at onset, nail dystrophy, extensive hair loss, and ophiasis (hair loss at the inferior hair line of the scalp [i.e., inferior-parietal/occipital scalp]).[2][9] Atopy may be an indicator of poor prognosis, but recent evidence is lacking.[2]

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