1 in 170 People in UK Have Experienced Alopecia Areata

Population Based Cohort Study highlights Important Factors Affecting Alopecia Areata

A large population based cohort study from the UK set out to describe the epidemiology of alopecia and sought to estimate incidence and prevalence rates, demographics and other important issues.

This population-based cohort study included 4.16 million adults and children. The authors accessed the UK electronic primary care records from the Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) network database over the period 2009–2018. This is a unique database as the RCGP RSC cohort is drawn from a large network of GP practices across England. The database is felt to be broadly representative sample of the UK population which makes is an helpful database to address important epidemiological questions.

The authors used the database to estimate the incidence and point prevalence of AA. Variation in AA incidence by age, sex, deprivation, geographical distribution and ethnicity was examined. Patterns of healthcare utilization were evaluated in people with incident AA.

Age was categorized into 5-year age groups. Ethnicity was grouped into standard major UK ethnic groups: white, black, Asian, mixed and other.  Socioeconomic status was defined using the Index of Multiple Deprivation (IMD). This classifies patients according to postcodes and gives some indication of socioeconomic status.   Evaluation of postal codes is a common research method to estimate socioeconomic status of an individual.

Results

Alopecia Areata Incidence and Prevalence

The AA incidence rate was calculated at 0·26 per 1000 person-years. This works out to be 1 in 3,846. In other words 1 in 3, 846 people in the UK population are estimated to develop new diagnosis of alopecia areata in the coming year. The AA point prevalence in 2018 was 0·58% in adults. This means that about 1 in 170 people in the UK have had alopecia at some point in their life or have it at the present time.

Alopecia Areata and Age

AA onset peaked at age 25–29  years for both sexes. The median age at diagnosis was 31 for males and 34 for females.

Alopecia Areata in Males vs Females

AA was slightly more common in females overall (IRR 1·19, 95% CI 1·13–1·24). For younger patients there did not really seem to be that much difference between males and females in terms of the chances of being diagnosed with alopecia areata. The real difference came after age 50. In those 50 and older, AA was more 2.12 times more common in women than men.

Alopecia Areata in Whites, Blacks and Asians

AA was substantially more common in nonwhite ethnicity groups with the highest incidence in Asians [IRR Asian vs. white ethnicity 3·32 (95% CI 3·11–3·55)]. The incidence of AA was similar in white patients as in black patients.

Alopecia Areata and Socioeconomic status and Location

The authors showed that patients with lower socioeconomic status were more likely to have alopecia areata than higher socioeconomic status. [IRR most vs. least deprived quintile 1·47 (1·37–1·59)]. People of lower socioeconomic status were less likely to be referred for specialist dermatology review compared to those of higher socioeconomic status

In addition, patients living in an urban area had a very slightly increased risk for alopecia areata compared to those living in rural area. [IRR 1·23 (1·14–1·32)].

Alopecia Areata Treatments

Potent topical steroids were the most commonly prescribed medications in the year after a patient was diagnosis in the primary care setting.

Key Conclusions

This study of UK General Practice records provides some very useful and important information

1. First, one should take note that this study is one of the largest population-based epidemiological studies in the field of alopecia areata to date. The incidence of alopecia areata was estimated at 1 in 3846 people which is similar to other estimates. For example, a 2014 study by Mirzoyev and colleagues in the US put the estimate at 1 in 4760 people.

2. The prevalence of alopecia areata was 0.58 %. As hair specialists, many of us often tend to quote a magic number “2.1 %” when we speak about alopecia areata prevalence but this study reminds us that this may not be the most accurate number. It may be under this number. In fact, studies in France by Richcard and colleagues put the estimate closer to 1 %.

3. This study highlights the peak age in the mid 20s. This was also shown in a recent study by Gutierez and colleagues. We tend to think in the past that 50 % of patients develop alopecia areata before age 20 and 50 % develop alopecia areata after 20. This number may be a bit low. The data here suggests that 50% develop their first patch of alopecia areata before the early 30s and 50 % develop after the early 30s.

4. This study adds to the confusion as to whether different races have different chances of developing alopecia areata. In this particular study from the UK, patients of Asian background were more likely to have alopecia areata than white patients and the rates in black patients was similar to white patients. Other studies in the US have shown the rates of alopecia areata as being higher in black patients than white patients and some studies showing rates are lower in Asian patients than white patients. This confusion is a good thing not a bad thing as it simply tells us we don’t really full understand these issues yet.

5. This study also highlights that we’re probably both right and wrong when we keep saying that alopecia is just as common in women as in men. We tend to say it’s equal, but this really might not be accurate. It appears to be slightly increased in women compared to men and this is even more apparent in those over 50 where the rates are nearly two fold higher in women than men.

6. This study adds valuable new information about socioeconomic status and where exactly one lives. Patients living in cities and those with lower social economic status are at risk for alopecia areata. The exact reasons are not clear but could relate to stress as well as pollution for those living in cities. It could be related to dozens of other reasons to that haven’t even been considered. This is the first study to really highlight these 2 factors as risks.

REFERENCE

Harries M et al. The epidemiology of alopecia areata: a population-based cohort study in UK primary care. Br J Dermatol . 2022 Feb;186(2):257-265.

Mirzoyev SA, Schrum AG, Davis MDP et al. Lifetime incidence risk of alopecia areata estimated at 2.1% by Rochester Epidemiology Project, 1990–2009. J Invest Dermatol 2014; 134:1141–2.

Richard M-A, Corgibet F, Beylot-Barry M et al. Sex- and age-adjusted prevalence estimates of five chronic inflammatory skin diseases in France: results of the « OBJECTIFS PEAU » study. J Eur Acad Dermatol Venereol 2018; 32:1967–71.