title: Longitudinal Patterns of Emergency Department Visits: A Multistate Analysis of Medicaid Beneficiaries.
abstract: The objective of this study was to examine the longitudinal patterns of emergency department (ED) visits among adult fee-for-service Medicaid.
  
  
  
  Data were obtained from the Medicaid analytic eXtract files, Area Health Resource File, and County Health Rankings.
  
  
  
  A retrospective longitudinal study design, with four observations for each individual was used. The study population consisted of 33,393 Medicaid beneficiaries who met inclusion criteria. ED visits were time-lagged and time-varying patient-level factors were measured for each year. Time-invariant characteristics (gender and race/ethnicity) were measured in 2006. Multivariable hurdle models with logistic (ED use versus no ED use) and negative binomial regressions (ED visits among ED users) were used to analyze the ED visits over time. To account for correlation due to repeated observations, mixed effect models with robust standard errors were performed.
  
  
  
  In both unadjusted and adjusted analysis, the likelihood of ED use did not change from year to year (AOR = 1.00, 95 percent CI: 0.99, 1.01). Among ED users, the estimated number of ED visits increased over time (IRR = 1.01, 95 percent CI: 1.01, 1.03).
  
  
  
  Primary care resources should be a major focus to reduce the increased burden on the EDs.
authors.affiliation: School of Pharmacy, Department of Pharmaceutical Systems and Policy, West Virginia University, Morgantown, WV.
authors.forename: Parul
authors.initials: P
authors.lastname: Agarwal
authors.affiliation: School of Public Health, Department of Health Policy, Management, and Leadership, West Virginia University, Morgantown, WV.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Bias
authors.affiliation: School of Pharmacy, Department of Pharmaceutical Systems and Policy, West Virginia University, Morgantown, WV.
authors.forename: Usha
authors.initials: U
authors.lastname: Sambamoorthi
mesh_terms: D000328:Adult; D000367:Age Factors; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D004777:Environment; D005260:Female; D015438:Health Behavior; D006304:Health Status; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008484:Medicaid / Q000706:statistics & numerical data*; D008603:Mental Health; D008875:Middle Aged; D011320:Primary Health Care / Q000706:statistics & numerical data; D044469:Racial Groups / Q000706:statistics & numerical data*; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012737:Sex Factors; D012959:Socioeconomic Factors; D014481:United States
keywords: Medicaid; hospitals; time-series analysis