title: How many drinks did you have on September 11, 2001?
abstract: OBJECTIVE
  This study tested the predictability of error in retrospective self-reports of alcohol consumption on September 11, 2001, among 80 Vermont light, medium and heavy drinkers.
  
  
  METHODS
  Subjects were 52 men and 28 women participating in daily self-reports of alcohol consumption for a total of 2 years, collected via interactive voice response technology (IVR). In addition, retrospective self-reports of alcohol consumption on September 11, 2001, were collected by telephone interview 4-5 days following the terrorist attacks. Retrospective error was calculated as the difference between the IVR self-report of drinking behavior on September 11 and the retrospective self-report collected by telephone interview. Retrospective error was analyzed as a function of gender and baseline drinking behavior during the 365 days preceding September 11, 2001 (termed "the baseline").
  
  
  RESULTS
  The intraclass correlation (ICC) between daily IVR and retrospective self-reports of alcohol consumption on September 11 was .80. Women provided, on average, more accurate self-reports (ICC = .96) than men (ICC = .72) but displayed more underreporting bias in retrospective responses. Amount and individual variability of alcohol consumption during the 1-year baseline explained, on average, 11% of the variance in overreporting (r = .33), 9% of the variance in underreporting (r = .30) and 25% of the variance in the overall magnitude of error (r = .50), with correlations up to .62 (r2 = .38).
  
  
  CONCLUSIONS
  The size and direction of error were clearly predictable from the amount and variation in drinking behavior during the 1-year baseline period. The results demonstrate the utility and detail of information that can be derived from daily IVR self-reports in the analysis of retrospective error.
authors.affiliation: Vermont Alcohol Research Center, PO. Box 8505, Essex, Vermont 05451, USA. bperrine@varc.edu
authors.forename: M W Bud
authors.initials: MW
authors.lastname: Perrine
authors.forename: Kerstin E E
authors.initials: KE
authors.lastname: Schroder
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D047851:September 11 Terrorist Attacks; D011795:Surveys and Questionnaires