February 2004
Thickness, medullation and growth rate of
female scalp hair are subject to significant variation according to pigmentation
and scalp location during ageing.
Van Neste D.
Skinterface, 9, rue du Sondart, 7500 Tournai, Belgium. info@skinterface.be
The biological importance and/or significance of human hair colour is unknown
even though greying is obviously associated with ageing.
In order to further characterise hair pigmentation in relation with hair growth variables we
evaluated 3 scalp sites (top of the head (T): left and right and occipital(O))
in 12 untreated menopausal women (age range: 49-66 years: average 59.63 +/-
5.66) who presented complaining of hair loss and/or diffuse alopecia. Controls
were 12 non menopausal sexually mature woman (7 age range 15-21 and 5 age range
38-48) not complaining of hair loss.
One hair sample (whenever possible n = 60)
was taken one month after clipping from T and O on each person; menopausal women
were sampled twice. The following measures were performed with a light
microscope: diameter (average min-max., microm), medulla (0% = absent to 100% =
fully developed) and linear hair growth rate (mm/day).
The hairs were categorised as pigmented (P) or non-pigmented (white, W) as compared with a
black and white reference card. A total of 3343 hairs were analysed with
2-factor analysis of variance (ANOVA). A global comparison (all hairs) showed
that the average diameter of W hair (67.68 microm) exceeded that of P hair
(57.41 microm) (p = 0.0001) and this was maintained on all 3 scalp sites. In
addition, the medulla of W hair (23.91%) appeared more developed than the
medulla of P hair (12.21%) (p = 0.0001) and was more expressed in W T hairs as
compared with W O hairs (p = 0.0325).
There was also a significant interaction
between site and pigmentation (p = 0.0074). Growth rate of W hairs (0.38 mm/d)
was higher than that of P hairs (0.35 mm/d) (p = 0.0001) and there was a
significant variation according to scalp sites (p = 0.0001).
There was also a
significant interaction between site and pigmentation (p = 0.0062) with the
following rank order: O W (0.40 mm/d), T W (0.37 mm/d), O P (0.37 mm/d) and T P
(0.34 mm/d). Subgroups of W and P of paired thickness in the range of 50 to 80
pm consistently showed a 10% faster growth rate of W. Previous studies have
shown that growth rate and diameter declines in age and alopecia i.e. in hair
thinning.
Our data shows that the reduced growth rate of terminal hairs is in
fact limited to the pigmented hairs. The mechanisms by which white hairs are
spared these ageing changes are not yet understood. Less pigmented hairs are
usually undetected by photo- graphic techniques used for drug trials.
The
potential role of drug induced modifications of hair pigmentation should be
taken into account during the interpretation of efficacy except if
contrast-enhancement has been applied. Copyright John Libbey Eurotext 2003.
PMID: 14965792 [PubMed - in process]
 
Hair loss products and Hair loss treatments
|
