title: Factors contributing to the facial aging of identical twins.
abstract: BACKGROUND
  The purpose of this study was to identify the environmental factors that contribute to facial aging in identical twins.
  
  
  METHODS
  During the Twins Day Festival in Twinsburg, Ohio, 186 pairs of identical twins completed a comprehensive questionnaire, and digital images were obtained. A panel reviewed the images independently and recorded the differences in the perceived twins' ages and their facial features. The perceived age differences were then correlated with multiple factors.
  
  
  RESULTS
  Four-point higher body mass index was associated with an older appearance in twins younger than age 40 but resulted in a younger appearance after age 40 (p = 0.0001). Eight-point higher body mass index was associated with an older appearance in twins younger than age 55 but was associated with a younger appearance after age 55 (p = 0.0001). The longer the twins smoked, the older they appeared (p < 0.0001). Increased sun exposure was associated with an older appearance and accelerated with age (p = 0.015), as was a history of outdoor activities and lack of sunscreen use. Twins who used hormone replacement had a younger appearance (p = 0.002). Facial rhytids were more evident in twins with a history of skin cancer (p = 0.05) and in those who smoked (p = 0.005). Dark and patchy skin discoloration was less prevalent in twins with a higher body mass index (p = 0.01) and more common in twins with a history of smoking (p = 0.005) and those with sun exposure (p = 0.005). Hair quantity was better with a higher body mass index (p = 0.01) although worse with a history of skin cancer (p = 0.005) and better with the use of hormones (p = 0.05).
  
  
  CONCLUSIONS
  This study offers strong statistical evidence to support the role of some of the known factors that govern facial aging.
authors.affiliation: Cleveland, Ohio; and Temple, Texas From the Department of Plastic Surgery, University Hospitals, Case Western Reserve University; and Division of Plastic Surgery, Texas A & M Health Science Center College of Medicine.
authors.forename: Bahman
authors.initials: B
authors.lastname: Guyuron
authors.forename: David J
authors.initials: DJ
authors.lastname: Rowe
authors.forename: Adam Bryce
authors.initials: AB
authors.lastname: Weinfeld
authors.forename: Yashar
authors.initials: Y
authors.lastname: Eshraghi
authors.forename: Amir
authors.initials: A
authors.lastname: Fathi
authors.forename: Seree
authors.initials: S
authors.lastname: Iamphongsai