Is the apparent cardioprotective effect of recent alcohol consumption due to confounding by prodromal symptoms?

Previous research has reported a protective association between alcohol drinking and acute coronary heart disease in the 24-hour period after drinking. This study investigated whether this apparent protective association resulted from confounding due to the effect of prodromal symptoms on drinking behavior. In 1992, the authors conducted a case-control study that measured recent alcohol consumption and reasons for recent abstention from alcohol among patients with acute coronary heart disease identified from a community-based disease register and a representative control sample from the same community (Auckland, New Zealand). Cases were significantly more likely than controls to report recent abstention from drinking because they felt unwell. In unadjusted analyses, a protective association was observed between recent alcohol consumption and acute coronary heart disease; however, this association was weakened considerably after adjustment for the effect of prodromal symptoms on drinking behavior. The previously reported protective association between recent alcohol consumption and acute coronary heart disease appears to be largely due to the confounding effect of prodromal symptoms on drinking.