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January 14, 1998

Benzodiazepine Use and Crash Risk in Older Patients—Reply

Author Affiliations

Margaret A.WinkerMD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Senior EditorIndividualAuthor

JAMA. 1998;279(2):113-115. doi:10.1001/jama.279.2.113

In Reply.—Dr Amoroso et al suggest that tobacco use, not available in our study, may have confounded the association between benzodiazepine use and the risk of motor vehicle crash in the elderly. Given the lack of an effect with short-acting benzodiazepines, and the fact that tobacco use is unlikely to be differentially distributed according to the type of benzodiazepine (long- vs short-acting), confounding by tobacco use is unlikely to account for our results.

Drs Green and Wintfeld suggest that insufficient information was available to control for confounding by health status. We used the chronic disease score to obtain a measure of health status based on patterns of drugs dispensed in the year prior to the index date.1Thus, cardiovascular disorders, diabetes, and other chronic conditions and their severity are taken into account. Moreover, exposure to other drugs with central nervous system effects, including antidepressants, were controlled for separately in the analysis. It is unlikely that, after controlling for these accurate measures of health status, confounding would still be present.