title: Genetic vs Environmental Factors That Correlate With Rosacea: A Cohort-Based Survey of Twins.
abstract: OBJECTIVE
  To our knowledge, this is the first study on rosacea to formally define genetic and environmental contributions.
  
  
  OBJECTIVE
  To study a cohort of identical and fraternal twins to determine whether genetic factors contribute to rosacea development and, if genetic factors are present, quantitatively estimate the genetic contribution, as well as to identify environmental factors that correlate with rosacea by controlling for genetic susceptibility.
  
  
  METHODS
  Identical and fraternal twins were surveyed regarding risk factors implicated in rosacea. Faculty dermatologists determined a rosacea score for each twin participant according to the National Rosacea Society (NRS) grading system. Data were collected at the annual Twins Days Festival in Twinsburg, Ohio, on August 4-5, 2012, and August 2-3, 2013. Analysis was conducted for several months after each meeting. A cohort of 550 twin individuals, with most from Ohio, Pennsylvania, and the northeastern United States, participated.
  
  
  METHODS
  The NRS score and rosacea subtype were assessed using the NRS grading system and physical examination by board-certified dermatologists.
  
  
  RESULTS
  Among the 275 twin pairs (550 individuals), there were 233 identical twin pairs with a mean rosacea score of 2.46 and 42 fraternal twin pairs with a mean rosacea score of 0.75. We observed a higher association of NRS scores between identical vs fraternal twins (r = 0.69 vs r = 0.46; P = .04), demonstrating a genetic contribution. Using the ACE model (proportion of variance in a trait heritable secondary to additive genetics [A] vs the proportions due to a common environment [C] and unique environment [E]), we calculated this genetic contribution to be 46%. A higher NRS score was also significantly associated with the following factors: age (r = 0.38; P < .001) and lifetime UV radiation exposure (r = 0.26; P < .001). These associations remained after use of propensity score matching to adjust for multicollinearity. Other correlated variables included body mass index (r = 0.21; P < .001), smoking (r = 0.10; P < .02), alcohol consumption (r = 0.11; P = .01), cardiovascular comorbidity (r = 0.17; P < .001), and skin cancer comorbidity (r = 0.19; P < .001).
  
  
  CONCLUSIONS
  The study of twins allows us to separate genetic susceptibility and the influence of environmental factors affecting rosacea. We found that approximately half of the contribution to the NRS score could be accounted for by genetics and the other half by environment. We identified correlations between rosacea and UV radiation exposure, alcohol, smoking, skin cancer history, cardiac comorbidity, and age. These findings may help improve current management and expectations of individuals affected by rosacea.
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Nely
authors: N
authors: Aldrich
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Meg
authors: M
authors: Gerstenblith
authors: Department of Epidemiology & Biostatistics, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Pingfu
authors: P
authors: Fu
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Marie S
authors: MS
authors: Tuttle
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Priya
authors: P
authors: Varma
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Erica
authors: E
authors: Gotow
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Kevin D
authors: KD
authors: Cooper
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors: Margaret
authors: M
authors: Mann
authors: Department of Dermatology, University Hospitals Case Medical Center, Cleveland, Ohio3Department of Pathology, Case Western Reserve University, Cleveland, Ohio4Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Oh.
authors: Daniel L
authors: DL
authors: Popkin
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000428:Alcohol Drinking / Q000009:adverse effects*; D015331:Cohort Studies; D004200:Diseases in Twins / Q000453:epidemiology / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012393:Rosacea / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D012907:Smoking / Q000009:adverse effects*; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014466:Ultraviolet Rays / Q000009:adverse effects*; D055815:Young Adult