New research by NIH’s National Institute on Deafness and Other Communication Disorders (NIDCD), with collaboration from the National Center for Complementary and Integrative Health (NCCIH), suggests that genetic factors provide some of the answers to the question of why African Americans seem to prefer mentholated cigarettes over other flavors. The research was funded in part by the NIH intramural research program and the FDA through an interagency agreement through funds via the Family Smoking and Prevention and Tobacco Control Act, as well as by NIH through several of its institutes. The study was published in a recent issue of PLOS Genetics.
Commonly added to cigarettes and other tobacco products, menthol may reduce the harshness of cigarette smoke due to its cooling and anesthetic properties. Although overall rates of cigarette smoking have declined sharply during the last 50 years, smoking mentholated cigarettes has increased in some groups. Today, nearly 86 percent of African-American smokers use menthol-flavored cigarettes compared to 32 percent of Hispanic smokers and 24 percent of Caucasian smokers.
The researchers conducted genetic analyses in a multiethnic group of 561 people from Dallas, TX, an independent group of African Americans in Dallas, and a group of 741 African Americans from Washington, D.C. They found that a specific set of DNA variations (or polymorphisms) that tend to be inherited together was associated with as much as an eightfold increase in the odds of menthol cigarette smoking. Specifically, they identified a genetic variant of MRGPRX4, which encodes a G-protein coupled receptor expressed in sensory neurons (and may play a role in sensing irritation). The variant is denoted as rs7102322, and was seen exclusively in individuals of African descent.
The scientists, however, also report that the MRGPRX4 variant associated with menthol cigarette smoking is relatively uncommon, so it’s unlikely that this variant alone accounts for all of the difference in menthol cigarette smoking between African Americans and other ethnic groups. The researchers say the existence of population-specific genetic variants presents a new risk factor for menthol cigarette use, and they suggest that its existence can inform health policies and tobacco regulatory actions designed to reduce U.S. health disparities.
- Kozlitina J, Risso D, Lansu K, Olsen RH, Sainz E, Luiselli D, Barik A, et al. An African-specific haplotype in MRGPRX4 is associated with menthol cigarette smoking. PLOS Genetics. February 15, 2019. Epub ahead of print.