The scientists from the University of Alabama, Birmingham (UAB) say drinking alcohol while inhaling second-hand smoke increases the damage cigarette smoke has on the heart.

The researchers reached this conclusion after conducting a study on mice in the laboratory and say second-hand smoke or directly smoking while drinking alcohol, is nearly five times worse than breathing fresh air and not drinking alcohol.

For the study the mice were exposed to smoky air in a lab enclosure while being fed a liquid diet containing ethanol (the intoxicating ingredient in alcohol).

The researchers found that the combination increased by almost 5 times the presence of artery lesions, compared to mice breathing normal air and eating a normal diet.

Experts say artery lesions are a common problem in heavy smokers and a sign of advancing cardiovascular disease.

The combination of alcohol and tobacco also was worse than taking tobacco without alcohol and drinking alcohol without tobacco.

The researchers say mice solely exposed to the smoky air had a 2.3-fold increase in artery lesions when compared to mice who breathed filtered air; mice solely fed a liquid diet containing ethanol had a 3.5-fold increase in artery lesions when compared to mice fed a normal diet.

The UAB team also looked at other signs of advancing cardiovascular disease such as DNA damage and oxidative stress in key heart tissues and they believe their findings are significant because moderate alcohol consumption is commonly thought to be cardioprotective.

Shannon Bailey, an associate professor in the UAB Department of Environmental Health Sciences and a co-investigator on the study says the findings are important for smokers and non-smokers alike in terms of what they should and should not do to protect their health.

The mice experiments were performed over a five-week period, and blood-alcohol concentrations reached the equivalent of a 150-pound adult consuming two drinks per hour; cigarette smoke exposure was similar to being in an automobile with a chain smoker with the windows closed.

The researchers say the combination of the smoky air and the ethanol had the effect of negating any potential heart benefit from drinking alcohol by itself.

Lead researcher, Scott Ballinger, who is an associate professor in the UAB Department of Pathology, says the study shows that exposure to cigarette smoke when combined with alcohol consumption caused the greatest degree of cardiovascular disease development compared to either action or exposure alone.

The study is published in the journal "Free Radical Biology & Medicine."