title: Correlated measures in longitudinal analysis of daily drug use patterns in a general intensive care unit.
abstract: OBJECTIVE
  The objective of the present study is to compare two different study designs (with and without corrections for correlated measures) to identify possible determinants of psychotropic drug use in an intensive care unit (ICU).
  
  
  METHODS
  In a logistic regression analysis, odds ratios (OR) were calculated for days in which patients were exposed to psychotropics compared with non-exposed days. In order to adjust for correlated measures, logistic regression with a logistic binomial model was applied.
  
  
  RESULTS
  We found that adjustment for correlated measures did not result in major changes in the OR. However, with more observations per patient parameter, adjustment for correlation has greater effect.
  
  
  CONCLUSIONS
  Adjustment for correlated measures may be useful in longitudinal drug analyses.
authors.affiliation: Altrecht Institute for Mental Health Care, Den Dolder, The Netherlands. j.stolker@altrecht.nl
authors.forename: Joost J
authors.initials: JJ
authors.lastname: Stolker
authors.forename: Eibert R
authors.initials: ER
authors.lastname: Heerdink
authors.forename: Frans G
authors.initials: FG
authors.lastname: Zitman
authors.forename: Hubert G M
authors.initials: HG
authors.lastname: Leufkens
mesh_terms: D018806:APACHE; D000328:Adult; D000368:Aged; D001509:Bed Occupancy / Q000706:statistics & numerical data; D001569:Benzodiazepines / Q000627:therapeutic use; D015986:Confounding Factors, Epidemiologic; D017723:Drug Utilization Review / Q000706:statistics & numerical data*; D005260:Female; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007902:Length of Stay / Q000706:statistics & numerical data; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D017891:Pharmacoepidemiology; D011619:Psychotropic Drugs / Q000145:classification / Q000627:therapeutic use*; D012189:Retrospective Studies
chemical_list: D011619:Psychotropic Drugs; D001569:Benzodiazepines