Evaluating recall bias in a case-crossover design estimating risk of injury related to alcohol: data from six countries.

INTRODUCTION AND AIMS: Prior work suggests that recall bias may be a threat to the validity of relative risk estimation of injury due to alcohol consumption, when the case-crossover method is used based on drinking during the same six hours period the week prior to injury as the control period. This work explores the issue of alcohol recall bias used in the case-crossover design. DESIGN AND METHODS: Data were collected on injury patients from emergency room studies across six countries (Dominican Republic, Guatemala, Guyana, Nicaragua, Panama and Canada), conducted in 2009-2011, each with n ≈ 500 except Canada (n = 249). Recall bias was evaluated comparing drinking during two control periods: the same six hours period the day before versus the week before injury. RESULTS: A greater likelihood of drinking yesterday compared with last week was seen using data from the Dominican Republic, while lower likelihood of drinking yesterday was found in Guatemala and Nicaragua. When the data from all six countries were combined, no differential drinking between the two control periods was observed. DISCUSSION AND CONCLUSIONS: These findings are in contrast to earlier studies showing a downward recall bias of drinking, and suggest that it may be premature to dismiss the last week case-crossover method as a valid approach to estimating risk of injury related to drinking. However, the heterogeneity across countries suggests that there may be some unexplained measurement error beyond random sampling error.