Objectives: To develop a reproducible photonumeric scale to assess photoprotected skin aging and to determine whether health and lifestyle factors, such as smoking, affect skin aging in photoprotected sites. Design: Using standard photographs of participants' upper inner arms, we created a 9-point photonumeric scale. Three blinded reviewers used the scale to grade the photographs. Participants answered multiple lifestyle questions. Setting: Academic outpatient dermatology clinic. Participants: Eighty-two healthy men and women aged 22 to 91 years. Interventions: A professional medical photographer took standardized photographs of each participant's upper inner arm. Participants answered standardized health and lifestyle questions. Main Outcome Measures: (1) Interobserver agreement and reproducibility using the photonumeric scale and (2) health and lifestyle factors most predictive of the degree of aging in photoprotected skin. Results: There was good blinded interobserver agreement as measured by the maximum range of disagreement scores for each participant (mean, 0.91; 95% confidence interval, 0.76-1.06). Results were reproducible. We developed a multiple regression model showing that the best model for predicting the degree of aging in photoprotected skin includes 2 variables: age and packs of cigarettes smoked per day. Conclusions: This photonumeric scale demonstrates good interobserver agreement and good reproducibility. Using this scale, the degree of aging in photoprotected skin was significantly correlated with patient age and a history of cigarette smoking. Additional studies are needed to continue garnering information regarding independent risk factors for aging of photoprotected skin.
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