Most studies that have found a link between alcohol consumption and coronary health over the last 30 years have shared a common flaw that could invalidate their results, according to researchers at the University of California at San Francisco (UCSF).

The San Francisco Chronicle reported March 30 that a review of past studies on alcohol and heart health found that nearly all included former drinkers in the group of "abstainers" who were compared to moderate drinkers. The researchers said this was a mistake because many former drinkers quit consuming alcohol because of advanced age or poor health, making the "abstainers" group appear less healthy compared to the moderate drinkers.

Most of the studies concluded that moderate drinkers had better coronary health than nondrinkers. The UCSF said that if the former drinkers are taken out of the equation, the heart health of both groups is about the same.

"This reopens the debate about the validity of the findings of a protective effect for moderate drinkers, and it suggests that studies in the future be better designed to take this potential error into account,'' said study lead author Kaye Fillmore.

The error actually was first noted by researchers in 1998, but later studies continued to lump former drinkers and lifelong abstainers together. Only seven of the 54 studies reviewed by researchers at UCSF, the University of Victoria in British Columbia, and Curtin University in Australia separated these groups of subjects.

Other researchers said that a randomized trial -- where one group is assigned to drink moderately over the course of years and is compared to a group of abstainers -- is needed to overcome the flaws in studies of alcohol and coronary health.

The study appears in the online edition of the journal Addiction Research and Theory.