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Alopecia
areata epidemiology and clinical disease patterns
Epidemiology, the study of the distribution and determinants
of health conditions in human populations, was originally concerned
with the investigation and control of infectious diseases, but
now has evolved into a powerful tool for analyzing many kinds
of health events, including occurrence and prevalence of alopecia
areata. Epidemiological information with respect to alopecia areata
obtained from study samples of a target population is as crucial
to the disease description as clinical and pathological findings
are.
Epidemiologic analysis and observations of alopecia areata are
available from USA, Japan and European countries, and this valuable
information is used to plan and evaluate strategies to prevent
hair loss, and as guide to management of patients in whom the
condition has already developed.
Alopecia areata is common throughout the world and can occur
at any age, but approximately 50 percent of cases are seen in
children and young adults before the age of 20. Statistical data
on the prevalence of alopecia areata in the United States, as
determined from the First National Health and Nutrition Examination
Survey conducted from 1971 through 1974, indicated that every
158 out of 100,000 persons, or roughly 0.1 to 0.2 percent of the
population, was affected by alopecia areata. Some research literature
has estimated that about 1.7% of the population presents at least
one episode of Alopecia Areata during their life. Both sexes are
equally affected, though some conflicting reports indicate a higher
incidence of alopecia areata in females or males.
Ikeda analyzed the case histories of 1,989 patients with alopecia
areata at Kyoto University in Japan and assigned them to one of
four arbitrary types of alopecia areata. Under the Ikeda classification
system:
- 83 percent of the cases were of Type I alopecia areata, characterized
by the "round" or patchy type of commonly found
alopecia areata. Individuals with type I alopecia areata had
no family
history of alopecia areata and carried a good prognosis, with
no history of hypertension, atopy, or endocrine disorders.
- 10
percent of cases in this study were categorized as Type II
(atopic type) alopecia areata, and was described as clinically
having hair loss in a round, ophiasis-patterned, reticular,
or indeterminate shape. These patients with type II alopecia areata
had a history of asthma, allergic rhinitis, or dermatitis.
The hair loss in these patients lasted longer than those with type
I alopecia areata and was associated with seasonal recurrences.
Over 75 percent of these patients went on to develop alopecia
totalis or total loss of scalp hair.
- Patients with type III
(prehypertensive type) alopecia areata had chronic disease activity
and a reticular pattern of hair
loss. This means that the patients experienced loss of hair in one site
concurrent with spontaneous hair re-growth in another area
of hair loss. The frequency of this type of alopecia areata was 4
percent, and alopecia totalis developed in 39 percent of these
cases. A point to be noted is that the incidence of parental
hypertension in this group was 95 percent, compared with 10 percent in the
common type, 11 percent in the atopic group, and 21 percent
in a control population.
- Patients with type IV (combined or endocrine-autoimmune)
alopecia areata were usually over 40 years of age and had
either round,
reticular, or ophiasis pattern (band like pattern of hair
loss affecting the temporal and occipital regions of the scalp) alopecia
areata for a prolonged period. The frequency of this type
of alopecia areata was 3 percent, and alopecia totalis developed in 10 percent
of this group.
Studies by other investigators in due course have confirmed many
of Ikeda’s conclusions.
An evaluation study by Muller and Winkelmann of 736 patients
with alopecia areata at the Mayo Clinic between 1945 and 1954
reported that 30 percent of patients developed alopecia totalis
(54 percent of the children and 24 percent of the adults). They
also observed that the proportion of patients presenting with
alopecia totalis declined with each decade of life.
In an attempt to co-relate puberty and prognosis of alopecia
areata patients, Walker and Rothman reviewed 230 patients with
alopecia areata at the University of Chicago Clinics during the
period from 1928 to 1948. This included 40 patients who went on
to develop alopecia totalis or alopecia universalis. They reported:
- Of those patients who developed alopecia areata before puberty,
50 percent eventually developed alopecia totalis and none
fully recovered from the episode.
- In comparison, only 23 percent
of those who developed patchy alopecia areata after puberty
became totally bald and only 5 percent
of these patients fully recovered.
- The duration of the initial alopecia areata
episode until complete hair re-growth was within 6 months in
31 percent of the
patients and within 1 year in 50 percent. They also pointed out that 34
percent of the patients never recovered from the initial
episode.
- The overall incidence of relapse or of experiencing another
episode of alopecia areata was 86 percent, although it reached
100
percent if patients were followed for 20 years. Those patients with alopecia
totalis tended to remain persistently bald.
Detailed data on the natural history of alopecia areata and on
the epidemiology of disease is useful information that helps researchers
to understand who gets this disease, how it progresses, and its
co-relation with the other diseases with which it is associated.
Human epidemiology shows that there is a higher incidence of alopecia
areata in genetically related individuals, suggesting that genes
affect alopecia areata.
Epidemiological studies to investigate associations between alopecia
areata and MHC class II antigens have helped to spur research
towards uncovering the possible autoimmune pathogenesis of alopecia
areata. The documentation of this data also helps new investigators,
who do not have access to their own group of carefully defined
alopecia areata patients, to conduct immunologic and other studies,
in the hope of discovering the dark secrets of this enigmatic
disease.
Alopecia
areata epidemiology and clinical disease patterns references
- Safavi K. Prevalence of alopecia areata in
the First National Health and Nutrition Examination Survey.
Arch Dermatol. 1992 May;128(5):702. PMID:
1575541
- Safavi KH, Muller SA, Suman VJ, Moshell AN,
Melton LJ 3rd. Incidence of alopecia
areata in Olmsted County, Minnesota, 1975 through 1989. Mayo
Clin Proc. 1995 Jul;70(7):628-33. PMID: 7791384
- Ikeda T. A new classification of alopecia
areata. Dermatologica. 1965;131(6):421-45. PMID: 5864736
- Muller SA, Winkelmann RK. Alopecia areata an evaluation of
736 patients.
Arch Dermatol. 1963 Sep;88:290-7.
PMID: 14043621
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