Variations in facial skin thickness and echogenicity with site and age.

The characteristic pattern of reflectivity of facial skin, as evaluated by ultrasound, has not previously been described quantitatively. The aim of this study was to evaluate site- and age-dependent variations in skin thickness and echogenicity of facial skin. A total of 40 women, in different age groups, were studied at 12 different facial skin sites. Echographic images were recorded with a 20 MHz B-Scanner and processed by dedicated software. Skin thickness measurements showed significantly higher values on the lower part of the face, whereas skin echogenicity was higher on the upper part of the face. In elderly subjects, an increase in facial skin thickness and overall echogenicity was observed compared with the younger subjects at all assessed skin areas, except the infraorbital regions. Moreover, modifications of skin echogenicity according to age, consisting in the appearance of a subepidermal band and an enhancement of the lower dermis' reflectivity, were observable at most facial skin sites.     

Quantitative evaluation of chronological ageing and photoageing in vivo: studies on skin echogenicity and thickness

Skin ageing is divided into chronological ageing and photoageing due to the cumulative effects of solar ultraviolet radiation. It is, however, difficult to measure the degree of photoageing and chronological ageing in humans in vivo . Here, we have evaluated the usefulness of ultrasonography for measurement of chronological ageing and photoageing in vivo . Twenty megahertz ultrasonography was performed in 90 individuals (29 men, 61 women, age 18–94) to describe age-related changes in sun-exposed regions with different levels of sun exposure (dorsal and ventral forearm, forehead, ankle) and non-exposed buttock skin. Skin thickness and skin echogenicity in different layers of the dermis were measured in ultrasound images. Additionally, cutaneous photodamage was scored clinically. Age-related changes were dependent on body site as well as layer of the dermis. A progressive, age-related decrease in echogenicity of the upper dermis was found in sun-exposed regions (dorsal forearm, forehead), but not in moderately exposed regions (ventral forearm, ankle). In the buttock an increase in echogenicity was observed. The echogenicity of the lower dermis increased in all examined sites. Skin thickness increased with age in the forehead and buttock, but decreased in the extremity skin. Our findings show that photoageing causes a decrease in echogenicity in the upper dermis. In contrast, chronological ageing is associated with an increase in echogenicity in the lower dermis. Although both increases and decreases in skin thickness were observed in different anatomical regions, there was no general relationship between skin thickness and age. Dermal echogenicity was deemed valuable for in vivo study of chronological ageing and photoageing.     

Influence of age on the wrinkling capacities of skin

Background: Comparisons of clinical assessment with measurement of physical parameters are rare.
Objective: To standardize the horizontal wrinkling of the skin in order to define a reference chart of the different wrinkling grades and to propose an interpretation of the clinical pattern in terms of skin layers thickness and mechanical parameters.
Methods: A device allowing reproducible wrinkling of the skin was made. The skin folds created in this way were clinically assessed on women of different ages. Measurements of the mechanical properties of the skin were carried out by using a Torquemeter. Skin layers' thicknesses were measured by using in vivo Confocal Microscopy (CM) and Ultrasound Imaging (B mode).
Results: Skin wrinkling grades increase versus age. Skin elasticity, extensibility and echogenicity decrease also versus age and the wrinkling grade. Wrinkling appears to be related to skin rigidification (for both stratum corneum and dermis) coupled to a certain weakening of the upper dermis (loss of echogenicity).
Conclusion: This study points out the key role of the age-related alterations of the upper dermis in skin wrinkling capacities.     

20MHz与50MHz超声皮肤成像与测量的比较研究

目的 了解20 MHz和50 MHz两种超声频率下人体不同部位皮肤的成像特点,比较两种频率超声测量皮肤厚度时的信度.方法 招募健康志愿者39名,年龄18 ～ 39岁.采用20 MHz和50 MHz超声对受试者全身20个部位皮肤进行超声成像,由3名医师分别测量各人体部位表皮与真皮的厚度,分析超声图像,并通过计算组内相关系数判断不同频率超声测量不同部位皮肤厚度时的信度.结果 两种频率超声测量各部位表皮时组内相关系数基本小于或接近0.7,信度不理想;在光滑平坦的人体部位,两种频率超声测量真皮时组内相关系数基本大于0.75,信度较高.20 MHz超声可以充分显示真皮与部分皮下组织,50 MHz超声仅能显示真皮层结构,但对细节成像更清晰.在一些解剖结构复杂且不平整的部位,两种频率超声在成像深浅、细节分辨能力方面各有利弊.结论 20 MHz和50 MHz超声作为无创影像工具能够很好地反映表皮及真皮结构;在人体不同部位,要根据两种频率超声的成像特点进行选择.     

Dermal fluid translocation is an important determinant of the diurnal variation in human skin thickness

BACKGROUND: Ultrasonography has been used as a non-invasive approach to measure skin thickness. To date there have been no studies on diurnal variations in skin thickness. OBJECTIVES: To evaluate diurnal variations in skin thickness and to compare these with corresponding echogenicity and skin elasticity. METHODS: Measurements by ultrasonography B-mode and by Cutometer SEM 575 were carried out in the morning and in the afternoon on 20 men and 20 women (mean age 30 years) on three areas of the face (forehead, corner of the eye and cheek), the forearm and the upper arm, and the flank, thigh and calf. RESULTS: From the morning to the afternoon, the skin thickness in both sexes significantly decreased on three areas of the face, the forearm and the upper arm, but significantly increased on the thigh and calf. In parallel, the echogenicity significantly increased from the morning to the afternoon on the three areas of the face, the forearm and the upper arm, but decreased significantly on the thigh and calf. Measurements of mechanical properties at four sites demonstrated that from the morning to the afternoon, the major parameters of skin elasticity Ue* and Uf* increased significantly in both sexes on two areas of the face and slightly on the forearm, but decreased significantly on the calf. CONCLUSIONS: The diurnal profiles of skin thickness and skin elasticity in the upper half of the body are the reverse of those in the lower half of the body. These findings suggest that shifts of dermal fluid from the face to the leg by gravity during the day cause the diurnal variation in skin thickness.     

Age-related alterations of echogenicity in Japanese skin

BACKGROUND: Ultrasonic methods are commonly used for the noninvasive measurement of skin thickness. The effects of ageing on the skin have been reported to differ between Asians and Caucasians. Therefore, it is possible that the echogenicity of the skin on ultrasonographic images reflects differences in the skin architecture and properties that may vary among races and environments. OBJECTIVE AND METHODS: Since there have been a few reports on ageing-related changes in ultrasonic echogenicity in Caucasian skin, but not in Asian skin, we evaluated age-related changes in the echogenicity of ultrasonographic images by the ultrasonic B mode at 3 sites on the face (forehead, eye corners, cheeks) considered as sun-exposed areas and on the ventral forearms considered as weakly sun-exposed areas in 130 Japanese females aged from 18 to 83 years. The dermis was divided into 3 layers (upper, middle, lower), and echogenicity was evaluated in each area. RESULTS: No age-related change in echogenicity was observed in the entire dermis. When the dermis was divided into 3 layers (upper, middle and lower dermis), the echogenicity was decreased in the upper layer and increased in the lower layer with age in all skin areas tested. In contrast, there were no age-related changes of echogenicity in the middle dermis. CONCLUSION: These findings suggest that, as for Caucasians, echogenicity in the upper and lower dermis is a useful tool for evaluating skin ageing in the Japanese.     

Non-invasive evaluation of inflammation in atopic dermatitis*

In atopic dermatitis the inflammatory reaction is quantified either clinically or histologically. While clinical evaluation has the major disadvantage of inter- and intraoperator variance, histological investigation requires invasive procedures. Therefore, standard techniques which provide both an objective and non-invasive form of examination are desirable. We investigated 20 patients with atopic dermatitis by means of high resolution 20-MHz b-*scan ultrasound. Investigations were performed on inflammatory skin lesions at regular intervals using a standardized combination of external treatment with α-methyl-prednisolon-aceponat ointment and UV-A/UV-B phototherapy until the lesions had healed. Skin colour (erythema) was assessed with the Minolta Chromameter CR 200 colorimeter according to the L*a*b* colour system. Sonograms of affected skin show a zone of low echogenicity below the so-called entry-echo. We refer to this as the echolucent area. Healing of a lesion is seen as a decrease in thickness and an increase in density of the skin in the sonographic image; the echolucent area disappears totally when the lesion has clinically healed. In five patients we excised small areas of skin to compare the sonographic and histological pictures of exactly the same site. This showed that the thickness of the subepidermal echolucent area corresponds to the inflammatory reaction representing both edema and cellular infiltration. Comparing the findings in sonography with the change in skin colour measurements we found that the a*-value of the L*a*b* colour system representing redness correlated well with the sonographic density of the echolucent area. In conclusion, 20-MHz-b-scan sonography and colorimetry are suitable methods for non-invasive, objective evaluation of the inflammatory process in atopic dermatitis.     

Reduced skin thickness: a new minor diagnostic criterion for the classical and hypermobility types of Ehlers-Danlos syndrome

BACKGROUND: The diagnosis of Ehlers-Danlos syndrome (EDS) is mainly based on clinical criteria, although in some instances a sound molecular diagnosis is available. Clinical signs can be divided into two categories: one with high diagnostic specificity and the other with low specificity. Despite the fact that reduced skin thickness is one of the dermatological features in patients with EDS, this issue has not been analysed in greater detail. OBJECTIVES: To determine skin thickness in patients with the classical and the hypermobility types of EDS. METHODS: In 21 patients with classical type of EDS and in nine patients with hypermobility type of EDS, skin thickness was analysed at different body sites by cross-sectional b-mode scans obtained with a 20-MHz ultrasound system. RESULTS: We found a significant decrease in skin thickness in both types of EDS, which was highest at the chest and at the distal part of the lower leg. CONCLUSIONS: We propose that the reduced thickness of the dermis as determined by high-resolution 20-MHz ultrasound can be used as a new minor criterion in the diagnosis of the classical and the hypermobility types of EDS.     

High-frequency ultrasound characterization of normal skin. Skin thickness and echographic density of 22 anatomical sites

Background/aims: Variation in skin thickness relative to anatomical site was little studied in the past. Biopsy cutting and histological processing change tissue geometry. High-frequency ultrasound allows in vivo measurement of skin thickness of multiple sites. The object was to map regional differences in skin thickness.
Methods: 22 different anatomical sites were studied. The Dermascan C (20 MHz) was used. The acoustic density of the dermis and the epidermal entrance echo was analyzed by the in-built image analysis software. 18 healthy volunteers aged 24-41 years were studied.
Results: Extremity skin was thinner than truncal skin, and acoustically dense. Females had thinner and more dense skin in comparison with males. Skin of the palm, sole and the head was thick but weak in density, and the biological variation in the dermis/subcutaneous tissue interphase does not allow highly accurate evaluation in these special sites. There was an overall inverse correlation between skin thickness and acoustic density with thin skin being dense and thick skin being relatively echo-poor.
Conclusions: Skin thickness and acoustic density reflecting intradermal structure exhibit systematic regional variation with thin and dense skin on extremities in comparison with the trunk and special ultrasound profiles in selected sites such as the face, the palp and sole. Female skin is thinner and more dense in comparison with male skin.     

Twenty MHz B-scan sonography for visualization and skin thickness measurement of human skin

As a non-invasive method, ultrasound is a suitable diagnostic procedure for routine in vivo examination of the human skin in dermatology. In this study 40 healthy test subjects were examined with a 20-MHz ultrasound scanner in order to determine the thickness and morphology of normal skin at 51 different sites. B-mode ultrasonography permits us to measure both the individual layers of the skin and deeper structures and to assess their definition and echogenicity. In both sexes the greatest skin thicknesses were found on: the shoulder-blade (mean thicknesses (mm), males 3.07/ females 2.47); the upper back (m, 3.04/f, 2.85); the chin (m, 3.04/f, 2.69); the lower lip (m, 2.66/f,2.50) and in the region of the lower back (m, 2.64/f, 2.39). Particularly thin skin was found on: the upper eyelid (m, 0.59/f, 0.64); the lower eyelid (m, 0.99/f, 0.86); in the groin (m. 0.97/f, 0.90); in the armpit (m, 1.01/f, 1.09) and on the forearm (m, 1.13/f. 1.00 mm). Knowledge of differences in the characteristic reflex patterns depending on the sex and age of the subject and the site of the skin examined forms the basis for assessment of pathological sonograms.     

Evaluation of the atrophogenic potential of different glucocorticoids using optical coherence tomography, 20-MHz ultrasound and profilometry; a double-blind, placebo-controlled trial

BACKGROUND: Skin atrophy is one of the main side-effects of topical corticosteroid therapy. Although the use of high-frequency ultrasound is an established method that has been studied previously, it allows measurements of the slow-reacting dermal thickness only. OBJECTIVES: To investigate the decreasing epidermal thickness, which occurs earlier, we used optical coherence tomography (OCT), a high-resolution noninvasive imaging technique, and compared it with 20-MHz ultrasound and profilometry. PATIENTS/METHODS: In this double-blind placebo-controlled trial 20 healthy volunteers applied four different corticosteroids and the cream base formulation as placebo to the volar part of both arms once a day over a 4-week period. The epidermal thickness, the dermal thickness and the skin surface roughness were assessed using OCT, high-frequency ultrasound and profilometry. RESULTS: Each of the three methods allowed the detection and monitoring of significant corticosteroid-induced skin atrophy and its reversibility. The changes correlated with the potency of the steroids. The epidermal thickness decreased significantly in all test areas, even in the placebo and the untreated fields. As expected, the reduction in epidermal thickness was more pronounced and could be detected earlier by OCT than the reduction of dermal thickness using ultrasound. The epidermal surface roughness investigated using profilometry showed a slight smoothing. CONCLUSIONS: OCT allows a simple, fast and noninvasive in vivo measurement of the epidermal thickness. To evaluate the atrophogenic potential of corticosteroids it is more suitable than high-frequency ultrasound as epidermal thickness decreases earlier. In addition, epidermal thickness is a more sensitive indicator of steroid atrophy as the degree of thinning is much higher compared with the dermal atrophy. Profilometry might give further information; however, it would not be suitable for clinical use as the results were generally less pronounced. In the future, OCT might be useful to detect corticosteroid-induced side-effects at the beginning for monitoring the therapy.     

Minimal erythema dose in UV-shielded and UV-exposed skin predicted by skin reflectance measured pigmentation

Aims: To investigate the relationships between epidermal thickness, age, skin pigmentation and UV sensitivity in sun-exposed skin and skin not exposed to the sun in healthy people without skin cancer or skin diseases. Methods: Phototesting with a xenon arc solar simulator was performed in 137 healthy Caucasians in buttock skin un-exposed to UV (27 children, 34 young adults and 32 older adults) and in skin of the back exposed to UV (44 young adults). The pigmentation of the phototest sites was measured objectively by a skin reflectance spectrometer before phototesting. Thickness of the stratum corneum and the cellular epidermis were measured in skin biopsies from the phototest sites. All measurements were performed in the winter and spring months. Results: Stratum corneum and cellular epidermis were thinner at the back than at the buttocks (P<0.01). Thickness of the stratum corneum at the back or the buttocks was not related to the degree of skin pigmentation (P=0.62 and P=0.20, respectively). Thickness of the stratum corneum at the buttocks was unaffected by gender (P=0.42) and age (P=0.83) whereas cellular epidermis decreased with age (P<0.01) and was thinner in females than in males (P<0.01). In spite of the higher pigmentation at the back than at the buttocks, the minimal erythema dose (MED) was lower at the back than at the buttocks (x=2.7 and x=2.2 SED's, respectively; P=0.04). Given the same degree of skin pigmentation, there was no difference in the MED in buttock skin in children, young adults and older adults un-exposed to UV (P= 0.61). Prediction of the MED in un-exposed buttock skin and in exposed skin of the back by a theoretical model based on an exponential function of the measured skin pigmentation was found to provide good estimates of the MED determined by phototest. Conclusion: Skin pigmentation at un-exposed buttock skin can reliably predict the constitutive UV sensitivity in healthy Caucasian children and adults and is recommended in surveys where phototesting cannot be performed.     

Echographic assessment of age-dependent variations of skin thickness

Background/aims: Skin thickness relative to age is complex and may be influenced both by intrinsic changes, extrinsic changes related to sun exposure and constitution, including sex. Age-related changes may also differ in different anatomical sites. The object was to characterize skin aging relative to these influences.
Methods: A-mode and B-mode high-frequency (20 MHz) ultrasound examination was performed using the Dermascan C. 162 subjects were examined (91 women, 71 men) in the age range 27 to 90 years. 6 anatomical locations (forehead, cheek, volar forearm, dorsal forearm, upper abdomen, buttocks) were studied.
Results: Females have thinner skin than men. Subjects aged more than 70 years have significant thinning of the skin. Age-related thinning is more pronounced in women. Relative skin-thickness decrease is less at sun-exposed areas in comparison with protected areas.
Conclusion: Ultrasund examination allows characterization of skin aging, and the influences of sex and anatomical site with sun-induced changes were differently superimposed on intrinsic changes and constitution.     

In vivo skin elasticity of 22 anatomical sites

Background/aims: Regional anatomical variations in bio-mechanical properties of skin were not mapped systematically in the past, despite the obvious clinical variation of this function. The object was to describe variations in skin distensibility and elasticity by the use of a suction chamber device.
Methods: 22 different anatomical sites were measured in 25 healthy volunteers aged 5-72 years. Anatomical sites were numbered systematically from the head toward the foot according to a vertical principle as a part of the study design.
Results: A systematic and vertically oriented decrease of distensibility and hysteresis from the head toward the foot was observed with a gradual increase of skin stiffness toward the ground. Skin elasticity decreased significantly with age. Acral female skin was more easily distended than male skin.
Conclusions: The vertical gradient of skin distensibility was described for the first time. This appears a prerequisite to resist the hydrostatic pressure and influences of gravity. The findings may have important implications in leg ulcer and gravitational syndrome.     

Skin thickness measurement by pulsed ultrasound; its reproducibility, validation and variability

The reproducibility of the pulsed ultrasound technique for the determination of skin thickness was investigated, using two independent observers. No systematic difference was found and a high correlation was obtained. Studies were also undertaken to validate the pulsed ultrasound technique as a measure of true skin thickness. Skin thickness determined in vitro was found to be greater than when in vivo determinations were made by either the pulsed ultrasound or a xeroradiographic technique, probably due to the release of in vivo tension within the dermis after excision. Skin thickness was found to increase linearly with age up to the age of 20 years and to decrease linearly with age subsequently. Differences in skin thickness between the sexes and in different sites of the body were demonstrated.     

Effect of dermal thickness, tissue composition, and body site on skin biomechanical properties

BACKGROUND/PURPOSE: Quantitative measurement of skin biomechanical properties has been used effectively in the investigation of physiological changes in tissue structure and function and to determine treatment efficacy. As the methods are applied to new questions, tissue characteristics that may influence the resultant biomechanical properties are important considerations in the research design. For certain applications, variables such as dermal thickness and subdermal tissue composition, as well as age and/or solar exposure, may influence the skin biomechanics. METHODS: We determined the influence of dermal thickness, tissue composition, and age on the skin biomechanical properties at the shoulder, thigh, and calf among 30 healthy females. We compared two devices, the Biomechanical Tissue Characterization System and the Cutometer SEM 575 Skin Elasticity Meter , to determine the effect of tissue sampling size. Dermal thickness was measured with 20 MHz ultrasound (Dermascan C) and tissue composition was inferred from anthropomorphic data. RESULTS: Skin thickness was significantly correlated with stiffness, energy absorption, and U(r)/U(f) for the shoulder. Body mass index (BMI) was significantly correlated with stiffness (negative correlation), energy absorption (positive), and skin thickness (negative) for the shoulder. Significant differences across body sites were observed. The calf was significantly different from the thigh and shoulders for all parameters (P<0.05, one-way anova). The calf had significantly lower laxity, laxity%, elastic deformation, energy absorption, elasticity, elasticity %, U(r), U(f), and U(r)/U(f) and significantly higher stiffness compared with the thighs and shoulders. sites. The thigh and shoulder sites were significantly different for all parameters except U(r)/U(f), elasticity %, laxity%, and stiffness. The dominant and non-dominant sides were significantly different. The dominant side (right for 90% of the subjects) had increased stiffness and decreased energy absorption (tissue softness, compliance) compared with the left side. A significant (P< or =0.02) negative relationship with age was seen for all biomechanical measures except stiffness at the shoulder. For the thigh and calf sites, significant negative correlations with age were found for elasticity %, U(r), and U(r)/U(f). Age and skin thickness were not correlated in this population. Skin thickness and age influenced the energy absorption at the shoulder site. The biological elasticity at the calf site could be predicted by age and BMI. The biological activity at the thigh site could be predicted by skin thickness and BMI. CONCLUSIONS: Significant regional variations in biomechanical properties and dominant side effects were observed. The biomechanical properties were significantly influenced by age. Certain properties varied with dermal thickness and tissue composition. The parameters were well correlated between the two instruments. The Cutometer, with its smaller aperture, was found to be more sensitive to age relationships.     

Characteristics of bacterial skin infections in children compared to adults at a tertiary dermatologic center

BACKGROUND: Bacterial skin infections in children and adults are caused by different organisms with different antimicrobial susceptibility. METHODS: A comparative retrospective study was carried out on 233 adults and 53 children with bacterial skin infections. Skin swab cultures and sensitivity tests were performed using standard methods. Statistical analysis was performed using the Pearson chi-squared and Fisher tests. A P value of < 0.05 was considered to be significant. RESULTS: Primary and secondary skin infections occurred in equal proportions in children, whereas secondary skin infections were more common in adults (70.8%). Staphylococcus aureus was the main cause of skin infections, particularly in children (72.6%). S. aureus in children and adults was highly susceptible to cloxacillin, cephalexin, chloramphenicol, neomycin, cotrimoxazole, and clindamycin, moderately susceptible to erythromycin, and insensitive to tetracycline, ampicillin, and penicillin. CONCLUSIONS: It is important to monitor the trends of bacterial infections and their antibiotic susceptibility as this can assist medical practitioners in their choice of antimicrobial therapy. Such monitoring will also help to detect the emergence of resistant bacterial strains and caution us to take care in the use of certain drugs.     

Age and skin structure and function, a quantitative approach (I): blood flow, pH, thickness, and ultrasound echogenicity

BACKGROUND/PURPOSE: The aging process has been studied with fervor recently, given our shifting demographics. Since age's effects are so manifest in skin's appearance, structure, mechanics, and barrier function, it is not surprising that much effort has been placed in research to better understand them. Quantitative measurements permitted by bioengineering have allowed us to objectively and precisely study aging skin. These overviews piece together the immense amounts of information that have emerged from recent technological advances in dermatological research in order to develop a unified understanding of the quantitative effects of age on the skin. METHODS: We performed a literature on age-related changes in blood flow, pH, skin thickness, and ultrasound imaging data, searching Pub-med, Em-Base, Science Citation Index, and the UCSF dermatological library's collection of books on the topic of aging skin. RESULTS: Despite the many tools and techniques available for quantitative analysis of skin, age studies are often conflicting, especially in the areas of blood flow and skin thickness. Trends indicate that blood flow may decrease with age, especially in sites exposed to the environment. pH apparently varies little until the age of 70, after which it declines. Skin thickness data are difficult to interpret; while the stratum corneum is generally accepted to maintain its thickness during aging, dermal, epidermal, and whole skin thickness changes are controversial. Ultrasound reveals the appearance of a subepidermal low echogenic band that thickens with age, especially in environmentally exposed areas. Some studies also indicate the presence of an echogenic band in the lower dermis which thins with increased age. However, the whole dermis appears to become more echogenic in elderly people. CONCLUSION: Much remains to be done if we are to reach consensus on the effects of age on skin structure and function. Future studies would be benefited by increased standardization of skin sites tested, methodology, and increased sample size.     

Ultrasonographic subepidermal low-echogenic band, dependence of age and body site

Background/purpose: The presence of an age-dependent subepidermal low-echogenic band (SLEB) is well established at specific body sites. Several studies have also proposed it to be a marker of photoaging, but only few studies have included children in their material, and UVR exposure has predominantly been evaluated as differences between body sites with different UVR exposure. The aim of this study was to further investigate the existence of SLEB and exploring its relation to both age and body site/UVR exposure.
Methods: In all 137 healthy volunteers from 4 to 68 years of age were included. In vivo high-frequency ultrasonography (B-mode, 20 MHz) was obtained from sun-exposed and sun-protected skin in a period with negligible environmental exposure to solar UVR. The SLEB was evaluated both visually and quantitatively.
Results: We found a significant correlation between visual scoring of SLEB and dermal echogenicity, which supports the usefulness of SLEB scoring.
We found that the grade (existence and development) of SLEB increased significantly with age at both the forehead and at the dorsal aspect of the forearm, where a well-defined SLEB was absent in children and present in over 50% of adults above the age of 40 years. No such age dependence was found either at the buttock or at the shoulder, and remarkably a well-defined SLEB was present in 37% of the adolescents at the buttock.
Conclusion: These results indicate that the age-related increase in SLEB grade at highly sun-exposed body sites might be attributed to UVR exposure. The presence of SLEB in both the young and at the sun-protected buttock points to a multifactorial etiology, where anatomical differences may play an important role as well as water content. SLEB might not be a very sensitive and specific marker of photoaging.     

Age-related changes in the elastic properties and thickness of human facial skin

Using recently designed, commercially available, non-invasive instruments, we measured the thickness and elasticity of the skin of the face and ventral forearm in 170 women, and evaluated the effects of age and exposure to sunlight. Skin thickness decreased with age in ventral forearm skin, which has limited exposure to sunlight, but increased significantly in the skin of the forehead, corners of the eyes, and cheeks, which are markedly exposed to sunlight. Skin elasticity (U_r/U_f) decreased with age on both the face and forearm. The ratio of viscosity element to elasticity element (U_v/U_e) increased with age at all sites. However, delayed distension (U_v), immediate retraction (U_r), final distension (U_f), and immediate distention (U_e), as individual elements, decreased on the face and increased on the forearm with age. This tendency was more marked after correction for skin thickness. These results suggested the specificity of skin thickness and elasticity in the facial skin. Analysis using a four-element model showed no changes in the elasticity coefficient of Maxwell element on the forearm, but an increase on the face. This indicates quantitative or qualitative changes in elastic fibres in facial skin. Thus, sunlight appears to have a considerable effect on the thickness and physical properties of facial skin.