Alopecia areata

Declaration of sponsorship Pfizer

Read time: 30 mins

Last updated:17th Sep 2023

Published:11th Apr 2023

Alopecia areata epidemiology

In this short and compelling video, Lynn Wilks recounts her first signs of alopecia areata and how they affected her.

Clinical variants of alopecia areata

Alopecia areata (AA) is a common form of non-scarring hair loss, that can involve total or near-total hair loss on the scalp, or on haired bodily surfaces. The clinical variants of AA are (Figure 1):

Patchy AA—single or multiple patches of hair loss, the most common subtype (Figure 1A)
Alopecia totalis (AT)—total or near-total loss of scalp hair (0.08–0.15%) (Figure 1B)
Alopecia universalis (AU)—total to near-total loss of hair on all haired surfaces of the body (0.01–0.07%)

Alopecia areata incognita—diffuse total hair loss with positive pull test, yellow dots, short, miniaturised, regrowing hairs but no nail involvement, resembles telogen effluvium

Ophiasis alopecia areata—band-like hair loss along the hairline (0.0–0.07%) (Figure 1C)
Sisaipho alopecia areata—extensive alopecia except around the periphery of the scalp
Marie Antoinette syndrome (canities subita)—diffuse alopecia with very sudden overnight greying and loss of pigmented hair

Clinical variants of alopecia areata

Figure 1. Clinical variants of alopecia areata. All photos used with permission by DermNet (https://dermnetnz.org/image-library). Attribution-non-commercial-noderivs 3.0 New Zealand (CC BY-NC-ND 3.0 NZ). (A) Circumscribed, “patchy” hair loss. (B) AA totalis with 100% scalp hair loss. (C) Hair loss of the occipital area (ophiasis AA). (D) Partial loss of eyebrows and eyelashes. (E) Patchy hair loss of the beard.

Alopecia areata epidemiology

AA affects people of all ages, including children and adolescents^1,2. Non-white populations are disproportionately affected¹.

Figure 2 illustrates the age and gender distribution in AA in the UK (Adapted²).

Age and gender distribution in alopecia areata in the UK

Figure 2. Age and gender distribution in alopecia areata in the UK (Adapted²).

Children and adolescents ≤18 years of age have an overall AA prevalence of 0.05% and commonly have a family history of AA^3,4. The presence of nail splitting and discolouration indicates severe disease and a poor prognosis. For most AA patients with less severe disease, hair loss resolves spontaneously within a year⁵.

People of Asian origin have a threefold higher AA incidence, and people from low-income and urban areas have a higher AA incidence⁶.

Although the burden of AA in North American countries is declining, it is still high in southern Latin America (9.41 age-standardised disability-adjusted life-years rates [DALY]), and Australasia (9.35 DALY)⁶.

Possible reasons for the lower rate of AA in North America are socioeconomic status, early detection, access to dermatologists and insurance coverage, underdiagnosis (less screening for skin conditions), and disease awareness^2,6.

Of people with alopecic patches persisting after one year, 30% develop AT, 15% develop AU. Prevalence rates of the more severe forms are 0.08–0.15% for AO and AT, and 0.01–0.07% for AU^7-10. Overall, AA follows a variable relapsing and remitting course that is difficult to predict.

Males and females are affected equally. Male patients tend to be diagnosed at a younger median age (31 years) than female patients (36 years) and have a poorer prognosis for hair regrowth than females¹¹. Figure 3 shows the proportion of people with AA referred for specialist dermatology review following diagnosis².

Proportion of people with alopecia areata referred for specialist dermatology review within 1 year of diagnosis, by calendar year

Figure 3. Proportion of people with alopecia areata referred for specialist dermatology review within 1 year of diagnosis, by calendar year (Adapted²). Orange shading represents 95% confidence intervals.

The younger the age of onset, the greater the lifetime likelihood of severe AA (AT and AU). Severe AA often co-occurs with atopic dermatitis, eczema, asthma, vitiligo, psoriasis, lichen planus, thyroid conditions, vitamin D deficiency and anaemia^11,12.