ARTICLE
Both intrinsic and actinic aging contribute to the development of the
elderly appearance of the skin. The study of photoaging should be performed
by comparison between anatomically similar portions of the body of the
same individuals. However, many of the studies conducted in the past have
utilized different skin regions of the same individuals for such comparison,
e.g., between the upper ventral arm and dorsal forearm [1] or between
the dorsal surface of the hand and that of the foot [2], or to use the
same locations of different people with various ages [3]. There are a
few studies [4, 5] that examined the skin of sun-exposed and adjacent
unexposed sites. As far as we know, however, there has been no study performed
on anatomically symmetrical sites of the same subjects for the evaluation
of photodamage. We have noticed that the dorsal skin of the right and
left hands of the people who frequently play golf show a different clinical
appearance. These golfers usually wear a glove on only one of their hands.
Therefore, one of their hands is exposed, whereas the other one is protected
by the glove from the outer environment, especially from sunlight. In
the present study, we examined the dorsal surfaces of the hands of the
same middle-aged golf players to determine the effects of photodamage
by using non-invasive measurements.
Materials and methods
Study I: biophysical study of the skin
Subjects
Twelve middle-aged healthy Japanese male subjects who had frequently
played golf from the morning to early afternoon approximately 5 to 6 hrs
a day at least twice or 3 times a month for the past 4 to 25 years participated
in the study after submitting informed consent (Table
I). All of them were right-handed and played golf with a glove
on only the left hand. One of them had used sunscreen on the right hand
while he played golf for the past 15 years. All of them were indoor workers
and have not been engaged in any other outdoor activities which would
expose their skin to sunlight. None of the subjects used moisturizer prior
to the study on the hands.
Non-invasive biophysical measurements
From November 1997 to March 1998, non-invasive bioengineering measurements
were performed on the skin of the dorsum of the hands. High frequency
conductance [6] to assess hydration state of the stratum corneum (SC)
was measured with Skicon®-200 (IBS, Hamamatsu, Japan).
Transepidermal water loss (TEWL) [7], a parameter for the water barrier
function of the SC, was measured with Evaporimeter® EP-1
(SevoMed, Stockholm, Sweden) according to the guideline [8]. Skin color
was determined with a Minolta CR-300 (Minolta, Osaka, Japan) chromameter
according to a 3-dimentional L* a* b* system, where L* is an attribute
on the luminance scale, a* on the red-vs-green attribute and b*
on the yellow-vs-blue attribute. All measurements were conducted
in an air-conditioned room with a room temperature of 16-22° C and
relative humidity of 21-50% after 15-min acclimation. The values obtained
were compared between the right and left hands (exposed and protected
hands during the play, respectively).
Study II: Morphological study of the skin surface
Subjects
A separate study on the skin surface contour was conducted from November
to December 1997 with 12 male Japanese golfers who had frequently played
golf from morning to early afternoon approximately 5 to 6 hrs a day at
least twice or 3 times a month for the past 4 to 25 years (Table
I). All were right handed and had a glove on only the left hand
during play. Two of them had used sunscreen on the exposed hand during
play for the past 15 and 20 years.
Replica analysis
Silicon rubber dental replicas (Shiseido, Japan) of the skin surface
were obtained from the dorsal surface of the hands to study the skin surface
microrelief. Replicas were obtained in a relaxed position with the palms
placed flat on the desk and other ones were taken when the subjects' dorsal
hands were in a slightly stretched position by gently holding a golf ball
placed on the desk.
The replicas obtained were processed using a skin surface replica
image analyzer [9, 10] (Shiseido, Japan). An image of 4 x 4 mm2
skin replica was obtained by illuminating it and feeding it into the computer
to calculate the various parameters. Among those parameters, KSD, depth
of the skin furrows, was compared between the right and left hands.
The replicas taken in the relaxed position were further analyzed by
scanning the surface approximately 1 cm perpendicularly to the direction
of the large wrinkles by laser profilometry. Roughness parameters, Ra
and Rz, were compared between the right and left hands. Ra represents
the area above and below an average line drawn at the central portion
of the profile. Rz is the average difference between the maximum heights
and nadirs in five equally spaced sections of the profile (Fig.
1).
Statistical analysis
The biophysical parameters obtained by non-invasive measurements and
those from the replica image analyzer were analyzed between the exposed
and protected skin by using Wilcoxon signed ranks test.
Results
Clinical appearance
The typical clinical feature of the dorsum of the hands of a 47-year-old
golfer with a 25-year playing history is shown in Figure
2. Although not so striking as that found on the photodamaged
skin of fair skined elderly people, there were more freckles on the skin
of the right hand, which was an exposed site during play. Moreover, the
right hand had a darker and coarser skin surface accompanied by wrinkles
compared to the left hand, which was always protected by a glove during
play. More or less similar differences in appearance were noticed in all
the golfers studied.
Biophysical non-invasive measurements of the
skin
Summary data are shown in Table
II. High frequency conductance values were significantly lower
on the exposed hand as compared to those on the left hand protected with
a glove (Fig. 3a). These
differences seemed to be dependent on the length of the past golf playing
history (data not shown). In contrast, there was no statistically significant
difference in TEWL values between the exposed right and protected left
hand. In the golfers, L* value was significantly lower on the exposed
skin than the protected one with such differences being dependent on the
length of the past golf playing history (data not shown). Although a*
and b* values were significantly higher on the exposed skin than the protected
hands, the differences in them were not dependent on the length of the
past golf playing history.
Morphological study of the skin surface
Computerized image analysis revealed that KSD values, means of the depth
of the fine furrows, on the exposed hand was significantly lower than
those on the protected hand (Table
II), although these changes were not dependent on the length of
the past golf playing history. Laser profilometry showed that Rz
and Ra values on the exposed hand were significantly higher
than those on the protected hand (Table
II). The differences were found to be larger in those with a lower
handicap (Fig. 4).
Discussion
Concerning intrinsic aging, some researchers reported a decrease in
skin surface hydration state [2, 11] whereas others pointed out that this
decrease was not always the case with every anatomical site [12]. In contrast,
there is no agreement as to the changes in the hydration state of the
skin surface with photoaging, although sun-exposed skin has been expected
to be drier on the basis of the clinical aspect. Histologically, the SC
of photodamaged skin shows variations. Some individuals have a typical
basket weave appearance, whereas others display compact or a mixture of
basket weave and compact appearance [13]. At any rate, the SC observed
under an ordinary microscope does not seem to be appreciably altered morphologically
by chronological aging [14].
Long time golf players display a distinct clinical difference between
the right and left hands, because one of them has been constantly protected
from the environment by a glove during play. In the present study, utilizing
this unique situation of the golfers' hands, we measured high frequency
conductance, which reflects the hydration state of the SC, to find that
it was significantly lower on the sun-exposed hand than on the hand protected
by a glove.
The results of the present study performed in middle-aged Japanese golfers
definitely indicate that chronic exposure to the outdoor environment induces
disorders in the keratinization process that contributes to the lower
hydration state in the SC of the exposed skin. We suspect that the dry
skin surface of the exposed hand in the golfers was produced mostly due
to the chronic sun exposure. However, the effects of other environmental
factors such as the exposure to dry air or wind should also be taken into
account. The occlusive effect caused by constantly wearing a glove during
the play might have also contributed to the hydrated state of the protected
skin. Moreover, the right hand was a more sun-exposed side since most
of them had driven a car with right-hand drive in Japan for a long time.
Not only the environmental influence but also their life style may affect
the skin conditions, since the exposed hands are also their dominant hands.
However, because we could not find such a difference between the right
and left hands of middle-aged Japanese indoor workers (data not shown),
the influence of these factors seems to be relatively small.
Although a decrease in TEWL, a parameter for the SC water barrier function,
with intrinsic aging has been reported by many investigators [2, 11, 12],
there has been no agreement on changes as to the TEWL induced by photoaging.
Our present results show that there is no difference in TEWL between the
sun-exposed skin and relatively protected skin, at least during the golf
play, of the same anatomical portion of the same individuals. Thus, the
skin barrier function does not seem to be impaired by the chronic exposure
at least until middle age.
One of the most distinct clinical changes of the hands was their color
difference between the right and left. The L*a*b* system is most frequently
used as biophysical parameters to quantify changes in skin color, in which
L* reflects luminance of the color, whereas a* and b* are on the red-green
and blue-yellow color scales, respectively. Photoaged skin is generally
described as yellowish with erythematous areas, also being associated
with telangiectasia and heterogeneity of skin pigmentation. Richard et
al. [5] found that standard errors of the mean values in L*a*b* were
larger in the exposed skin than those of the adjacent protected skin.
Their results seem to be consistent with such color heterogeneity in the
photoaged skin. Some authors reported that L* decreased, while a* increased
with photoaging [3, 5]. In contrast, others found no change in L*a*b*
[15]. Those who reported that L* and b* were decreased and that a* was
increased in the aged as compared to the young individuals conducted their
measurements on the ventral forearm [16], which is considered to be a
relatively photo-protected area. Taken together, a decrease in L* observed
in our study seems to occur in cutaneous aging both from the intrinsic
aging process and from the chronic UV light exposure.
To analyze skin surface contour, several methods are available including
computerized image analysis, mechanical and optical (laser) profilometry
[17, 18]. Our study of the skin surface contour with computerized image
analysis of microrelief showed that fine furrows became shallower on the
sun-exposed hand than the protected one. These results are consistent
with those of the study that showed less dense and less deep furrows on
the V zone of the neck than on the protected subclavicular zone situated
at a very adjacent area [5]. In regard to the reason why the difference
in the skin microrelief was not dependent on the length of the past golf
play history, we think that the skin phototype of the individuals influenced
the degree of dermal skin change. We found that, when the skin was relaxed,
large wrinkles or sags became more prominent on the exposed hand in golfers.
We showed that roughness parameters increased on the exposed skin as compared
to those of protected skin by laser profilometry. Moreover, the differences
became larger in those with a lower handicap and longer golf history.
We suspect that elastogenesis in the dermis of the photodamaged skin [15]
is related to this change. This tendency was also noted in the hands of
the middle-aged non-golfers although the difference was not statistically
significant (data not shown). We think that this change was mainly caused
by the sunlight exposure while driving, because most people drive on the
right side of the car in Japan.
We propose that our method of study utilizing the comparison between
the exposed and protected hand in the middle-aged golf players is a suitable
model to investigate skin aging (damage) influenced by our outer environment,
especially by sunlight, because these two sites are anatomically symmetrical,
showing the same intrinsic aging process. Such a study performed in more
fair-skinned Caucasian golf-players will provide much more clear out characteristics
of photodamaged skin.
Article accepted on 21/3/00
CONCLUSION Acknowledgements
The present study was supported by a grant from the Cosmetology Research
Foundation, Japan. Also the authors give the special thanks to Miss Yuko
Nagahamaya for her technical assistance.
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