Relative Contribution of Intrinsic vs Extrinsic Factors to Skin Aging as Determined by a Validated Skin Age Score

Second-order confirmatory factor analysis model used for development of partial and global skin aging scores. Correlation coefficients are indicated above the arrows. Correlations between each group of characteristics and corresponding partial scores, together with correlations between partial scores and the global score, were estimated using the CALIS procedure. Each partial score was then estimated as a weighted average for its centered-reduced characteristics, with weights corresponding to the correlations. The global score was obtained in the same manner, from the reduced partial scores. The formulas used for calculation of these scores are available on request.

Relationship between the skin age score and chronological age. Each individual is represented by an open circle. Skin age predicted by the model appears as a straight line (r= 0.88; P<.001) between age 31 years (upper limit for the first plateau) and age 71 years (lower limit for the second plateau). A to D indicate individuals whose photographs are depicted in Figure 3.

Photographs of women with a skin age score (SAS) less than their chronological age (A and C) and greater than their chronological age (B and D). A, A 41-year-old woman with an SAS of 28 and skin phototype IV. She used tobacco for 20 years and had moderate lifetime sun exposure. She was not experiencing menopause, and her body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters) was 21. B, A 42-year-old woman with an SAS of 55 and skin phototype IV. She smoked for 10 years and had severe lifetime sun exposure. She was not experiencing menopause, and her BMI was 21. C, A 57-year-old woman with an SAS of 49 and skin phototype IV. She was a nonsmoker, but her lifetime sun exposure was severe. She was experiencing menopause, and her BMI was 27 (overweight). D, A 57-year-old woman with an SAS of 64 and skin phototype III. She was a nonsmoker, but her lifetime sun exposure was severe. She was experiencing menopause, and her BMI was 24.