PHOTOAGING : HOW TO ASSESS IT?

AGING VERSUS PHOTOAGING

Cutaneous aging is a complex and multifactorial process; it implies both structural, functional and aesthetic changes happening at a variable rate [1].

The degree of visual alterations is under the dependence of combined processes [1]:

INTRINSIC AGEING

Chronological ageing linked to genetics

EXTRINSIC AGEING

Sun exposure, smoking habits, polluted environment

LIFESTYLE

Diet, sleeping patterns, alcohol or drugs consumption

HORMONAL STATUS

Menopause

CATABOLIC STATUS

Existence of chronic diseases (diabetes, cancer, infections, etc.)

Recently, Krutmann and his colleagues defined the concept of “skin aging exposome” [2]. It consists of “external and internal factors and their interactions, affecting a human individual from conception to death as well as the response of the human body to these factors that lead to biological and clinical signs of skin aging”. Sun radiations (ultraviolet UV, visible VIS, infra-red IR) are one of these environmental factors.

The impact of UV radiations on skin has long been studied. Already in 1969, Pr. Kligman evoqued their additional role in aging [3] and coined to the term “photoaging” to describe changes that develop after many years of cutaneous exposure to non-extreme, low doses of UV radiations [4]. One of the best-known example of “photoaging” is illustrated in figure 1, showing a 69-year-old man with unilateral dermatoheliosis (another term for photoaging) [5]. This man reported that he had driven a delivery truck for 28 years. Chronic UVA exposure, transmitted through window glass, resulted in the progressive thickening and wrinkling of the skin on the left side of his face.

Although we know, now, that VIS and IR radiations also have deleterious effects, the term “photoaging” still refer to chronic UV exposure. A randomized, controlled study conducted by the National Health & Medical Research Council of Australia for 4 years over more than 900 subjects demonstrated that daily sunscreen application (with UV filters) can specifically delay photoaging signs [6].

unilateral-dermatoheliosis_dermscan

Figure 1: Unilateral dermatoheliosis due to a 28-year-history of car driving [5]. 

PHOTOAGING: BIOLOGICAL EFFECTS AND CLINICAL SIGNS

Face, neck, chest and the back of the hands are the areas most affected by photoaging since they are UV-exposed nearly all year long.  80% of facial skin aging is attributed to UV-exposure [7].

At the physiological level, UV radiations amplify several mechanisms [8]:

While intrinsic aging corresponds to a thinned epidermis and fine wrinkles, the photoaged phenotype is characterized by fine and coarse wrinkles, skin dryness, skin laxity, pigmentation and vascular abnormalities (lentigines and telangiectasia respectively), sallow color and rough texture [9]. Histologically, the deposition of elastotic materials in the dermal connective tissue has long been considered a hallmark of photodamage (=solar elastosis) since it was found to correlate to the quantity of UV radiation received by the skin [10]. Endogenous protection systems (DNA repair systems, antioxidant defense, etc.) present in the skin influence the susceptibility toward photoaging [2]. Age groups or ethnic groups – due to different skin pigmentation –  may therefore present different clinical signs of photoaging [11].

Objective and reliable characterization of the degree of photodamage is important to evaluate the effect of treatments. Various clinical scores and grading systems have been proposed, accompanied or not of representative photographs: the SCINEXA [12], the Griffiths’ score [13], the Larnier’s score [14], the Glogau’s scale [15], etc. To date, there is no “gold standard” to assess photoaging [16-19]. Numerous non-invasive technologies can be useful to complete the clinical evaluation [20-25].

SOME INSIGHTFUL APPROACHES PROPOSED AT DERMSCAN TO EVALUATE PHOTOAGING

Photoaging management can be either preventive (e.g. sunscreen against UV damages) or curative (cosmetics to help reduce skin damages). In order to demonstrate the activity of your products on such process, long term studies must be conducted (at least 3 months). Thanks to our facility in Tunisia and our partner in Mauritius, we can also offer studies in sunny environments.

Depending on the activity of your product, multiple approaches can be combined to demonstrate its efficacy:

Cutaneous Parameters affected by photoaging and examples of Dermscan Methodologies to study them

3D images of skin deformation under air beam pressure (Dynaskin).

 

Firming effect before / after a 4 month treatment

Ultrasound images of the skin (DermaScan).

 

Increase in dermis density before / after a 3 month treatment

3D images of crow’s foot wrinkles (DermaTOP).

 

Decrease of wrinkle’s depth

2D images of skin relief and orientation lines (PrimosLite).

 

Increase in cutaneous isotropy with sunscreen

Sun spot images

 

Decrease in skin pigmentation and increase in cutaneous lightness after a 6 mont treatment

Red blood cell concentration map on the face (TiVi)

 

Vascular alterations with photoaging

Map of cutaneous moisture (Moisturemap).

 

Increase of moisture before / after a one month treatment

TEWL – Trans-Epidermal Water Loss – measurements (g/m²/h).

 

Normalisation of cutaneous barrier function of the skin after a 4 month treatment

Biochemical analysis of non-invasive superficial samples can provide information on the oxidative damages measured on lipids, proteins, enzymes as well as on the inflammatory status (interleukins).

These biometrological approaches complete clinical scoring with any of the well-recognized photoaging scales (Griffiths, Scinexa, Glogau, etc.).

Illustrative pictures taken in controlled conditions highlight the visual benefits obtained with your product…

REFERENCES

  1. Steventon K. Types of skin aging. Cosmetics & Toiletries. 2013; 128: 298-299.
  2. Krutmann J, Bouloc A, Sore G et al. The skin aging exposome. J Dermatol Sci. 2016;
  3. Kligman AM. Early Destructive Effect of Sunlight on Human Skin. J Am Med Assoc. 1969; 210: 2377-2380.
  4. Kligman LH, Kligman AM. The nature of photoaging: its prevention and repair. 1986; 3: 215-27.
  5. Gordon J, Brieva J. New Engl J Med. 2012; 366: 16.
  6. Hughes M, Williams G, Baker P, Green A. Sunscreen and prevention of skin aging: a randomized trial. Ann Intern med.2013; 158: 781-790.
  7. Uitto J. Understanding premature skin aging. N Eng J Med. 1997; 337: 1463-1465.
  8. Khol E, Steinbauer J, Landthaler M, Szeimies RM. Skin aging. J Eur Acad Dermatol. 2011; 25: 873-884.
  9. Kang S, Fisher G, Voorhees J. Photoaging. Clin Ger Med. 2001; 17: 643-659.
  10. Rees JL. The genetics of sun sensitivity in humans. Am J Hum Genet. 2004; 75: 739-751.
  11. Flament F, Bazin R, Laquièze S et al. Effect of the sun on visible clinical signs of aging in Caucasian skin. Clin Cosm Invest Dermatol. 2013; 6: 221-232.
  12. Vierkötter A, Ranft U, Krämer U et al. The SCINEXA: a novel, validated score to simultaneously assess and differentiate between intrinsic and extrinsic skin aging. J Dermatol Sci. 2009; 53: 207-211.
  13. Griffiths C, Wang T, Hamilton T et al. A photonumeric scale for the assessment of cutaneous photodamage. Arch Dermatol. 1992; 128: 347-351.
  14. Larnier C, Ortonne JP, Venot A et al. Evaluation of cutaneous photodamage using a photographic scale. Br J Dermatol. 1994; 130: 167-173.
  15. Glogau RG. Aesthetic and anatomic analysis of the aging skin. Semin Cutan med Surg. 1996; 15: 134-138.
  16. Kappes U, Elsner P. Clinical and photographic scoring of skin aging. Skin Pharmacol Appl Skin Physiol. 2003; 16: 100-107.
  17. Baillie L, Askew D, Douglas N, Soyer HP. Strategies for assessing the degree of photodamage to skin: a systematic review of the literature. Br J Dermatol. 2011; 165: 735-742.
  18. Yu S, Baron E. Evaluation and assessment of photoaging. Photon Lasers Med. 2013; 2: 305-314.
  19. Dobos G, Lichterfeld A, Blume-Peytavi U, Kottner J. Evaluation of skin aging: a systematic review of clinical scales.
  20. Gniadecka M, Jemec G. Quantitative evaluation of chronological aging and photoaging in vivo: studies on skin echogenicity and thickness. Br J Dermatol. 1998; 139: 815-821.
  21. Battistutta D, Pandeya N, Strutton G et al. Skin surface topography grading is a valid measure of skin photoaging. Photodermatol Photoimmunol Photomed. 2006: 22: 39-45.
  22. Miyamae Y, Yamakawa Y, Kawabata M, Ozaki Y. A noninvasive method for assessing interior skin damage caused by chronological aging and photoaging based on near-infrared diffuse reflection spectroscopy. Appl Spectrosc. 2008; 62:677-681.
  23. Bazin R, Laquièze S, Rosillo A, Levêque JL. Photoaging of the chest analyzed by capacitance imaging. Skin Res Technol. 2010; 16: 23-29.
  24. Wurm E, Longo C, Curchin C et al. In vivo assessment of chronological aging and photoaging in forearm skin using reflectance confocal microscopy. Br J Dermatol. 2012; 167: 270–279.
  25. Wheller L, Lin L, Chai E et al. Noninvasive methods for the assessment of photoaging. Austral J Dermatol. 2013; 54: 290-295.