Interaction of alcohol and tobacco in laryngeal cancer.

Both alcohol and tobacco use are accepted risk factors for laryngeal cancer. The authors used case-control data from previous studies to estimate the value of a previously proposed index of interaction between these two risk factors. In addition to the weighting procedure over exposure categories that was previously proposed for estimating a summary index, they applied maximum-likelihood techniques to facilitate the estimation. Overall, they found moderate synergy between alcohol and tobacco in increasing the risk of laryngeal cancer, in that exposure to both factors increased the risk about 50% more than the increase predicted if the effects of tobacco and alcohol were simply additive.