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The
Hamilton male pattern baldness classification system
In 1951 Dr James B. Hamilton developed the first useful classification
system with which to guage the extent of hair loss due to pattern
baldness in men. He examined 312 Caucasian males and 214 Caucasian
females aged between 20 and 89 years to produce the scale. He used
a classification system involving eight separate groups. In types
I to III of the Hamilton classification system there is no obvious
hair loss. Types IV to VIII categorized progressively more extensive
hair loss.
Type I is reserved for people with no hair loss. Hamilton
described it as "the abscence of bilateral recessions along
the anterior border of the hair line in frontoparietal regions".
In other words there is no evidence of a "widows peak".
Hamilton also suggested a variation on type I classed as type IA.
Type IA was reserved for men with a very high hair line on the forehead.
However this high hairline was not due to any hair line recession.
The high hairline was simply present as a result of genetic inheritance
and family features.
In developing the scale, he recognised that up to
96% of men and 79% of women reach at least hair loss stage two after
full pubertal sexual maturation. He claimed 58% of men over the
age of 50 had hair loss resembling patterns type V to type VIII
with the extent of hair loss stabilising at around 70 years of age.
He also claimed that by 50 years of age 25% of women had developed
type IV hair loss. The extent of hair loss apparently stabilised
once women were over the age of 50.
Hamilton claimed that more than 99% of men could
be classified according to his system. To prove the effectiveness
and easy use of his classification system he
recruited 4 attendants at a mental institution with no scientific
training. He gave each attendant a copy of his sketches and brief
descriptions of the classifications. The attandants studied for
half an hour and then used the information to classify 125 subjects
previously examined by Hamilton. It was found that the attendants
gave individuals the same classification as Hamilton 98% of the
time. This was simple but persuasive evidence that the classification
table was accurate and could be reliably used in a dermatology clinic.
The diagram below is a redrawing of Hamilton's original.
The
Hamilton male pattern baldness classification system references
- Hamilton
JB. Patterned loss of hair in man: types and incidence. Ana N
Y Acad Dermatol 1951:53;708-28
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