title: A cross-sectional analysis of U.S. contact lens user demographics.
abstract: OBJECTIVE
  Large population studies carried out in the United States, while addressing refractive error prevalence, have published little addressing the modes of refractive correction. As such, there are little data in the biomedical literature concerning the characteristics of the contact lens wearing population in the United States. The purpose of this project was to develop estimates of the demographic characteristics of a cross section of contact lens wearers in the United States based on those who wore contact lenses on the day of their National Health and Nutrition Examination Survey (NHANES) examination.
  
  
  METHODS
  The NHANES is a nationally representative sample of the U.S. population. As part of NHANES, the type of refractive correction used is collected during a mobile medical clinic examination along with demographic variables. Data files from the 2005-2006 and 2007-2008 NHANES were obtained from the National Center for Health Statistics. Demographic characteristics of the U.S. population using contacts during the medical clinic examination were derived. Associations between demographic variables and contact lens use were explored in age-stratified univariate and multivariate analyses taking into account the complex sampling frame.
  
  
  RESULTS
  In univariate analysis, age (p < 0.001) and the availability of health insurance (p = 0.007) have negative associations with contact lens use, while female gender (p < 0.001), higher socioeconomic status (p < 0.001), and higher educational attainment (p < 0.001) are associated with increased contact lens use. In multivariate analysis, age (p < 0.001), socioeconomic status (p < 0.001), the interaction of age with gender (p < 0.001), and the interaction of socioeconomic status with education (p = 0.002) are associated with contact lens use.
  
  
  CONCLUSIONS
  Four demographic variables, age, socioeconomic status, age-gender interaction, and socioeconomic status-education interaction, defined those likely to be using contact lens on any given day in the United States. Together, these four variables identify almost 9 of 10 contact lens users.
authors.affiliation: Department of Optometry, University of Alabama at Birmingham, 1716 University Blvd., Birmingham, AL 35294-0010, USA. mswanson@uab.edu
authors.forename: Mark W
authors.initials: MW
authors.lastname: Swanson
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003261:Contact Lenses / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012030:Refractive Errors / Q000453:epidemiology* / Q000534:rehabilitation*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D055815:Young Adult