Research shows that African-American smokers tend to have a tougher time quitting, and now a preliminary study suggests that darker skin, itself, may make people more vulnerable to nicotine dependence.

The study of African-American smokers found a correlation between their levels of the skin pigment melanin and their dependence on nicotine.

Studies have indicated that nicotine may bind to melanin, which is found not only in the skin, but also the eyes, hair, heart, lungs, liver and brain. It’s possible that the higher melanin levels in darker-skinned people may mean they store more nicotine, which could increase their level of dependence.

“The point of the study is that, if in fact, nicotine does bind to melanin, populations with high levels of melanin could indicate certain types of smoking behavior, dependence, and health outcomes that will be different from those in less pigmented populations,” lead researcher Gary King, a professor of biobehavioral health at Pennsylvania State University, said in a written statement.

“And the addiction process,” he added, “may very well be longer and more severe.”

King and his colleagues report their findings in the journal Pharmacology, Biochemistry, and Behavior.

  For their study, the researchers recruited 147 African-American men and women who were current smokers. All completed surveys on their smoking habits and degree of nicotine dependence; they were also tested for their levels of cotinine - a byproduct of nicotine that gives an objective measure of smoking levels.

The researchers used a device called a reflectometer to gauge melanin levels in each participant’s forehead and underside of the upper arm.

Because the forehead is regularly exposed to the sun, melanin levels there are higher and represent a mix of genetic and environmental influences. Melanin in the underarm area is largely genetically determined.

In general, King’s team found, higher melanin levels in the forehead corresponded to more frequent smoking, greater nicotine dependence and higher cotinine levels.

There was no clear connection between nicotine dependence and melanin in the underarm area.

The results raise the possibility that melanin plays some role in African Americans’ lower quit rates and higher rates of smoking-related diseases and death, according to King and his colleagues.

However, they write, while these findings are “interesting,” they must be considered preliminary.

“Further research on the link between melanin and nicotine among African Americans, as well as other population groups, is warranted,” they conclude.

SOURCE: Pharmacology, Biochemistry and Behavior, June 2009.