Menthol: it helps the poison go down easier
To me, the presentations appeared to suggest that right now the evidence that menthol cigarettes are more harmful to health is weak. However, the evidence that menthol cigarettes are a starter product for youth and that menthol cigarettes can (under certain circumstances) be more addictive and harder to quit, is quite strong and getting stronger all the time.
My own presentation focused on data we have previously published (and that I’ve already discussed on this blog) showing that menthol cigarettes are harder to quit for African Americans, Latinos and for people on a low income. It was very fortunate that just yesterday a new study by colleagues at UMDNJ-School of Public Health came into the public domain and so I was able to discuss its findings.
I think that study, by Drs Dan Gundersen, Cris Delnevo and Olivia Wackowski, is a very important one. The paper, which will be published in the journal “Preventive Medicine” and appeared online yesterday, was based on the 2005 National Health Interview Survey. It focused on a representative sample of U.S. adult ever exclusive cigarette smokers who had ever tried to quit (n=7,815). It aimed to assess whether people who were primarily menthol smokers had a lower quit rate than people who were regular cigarette smokers (after adjusting for other characteristics of those groups). The study found that among African American and Hispanic smokers, those who smoke menthols have a significantly lower rate of quitting. Interestingly it found that among whites, there was an opposite effect, with white menthol smokers having a slightly higher quit rate than white regular cigarette smokers.
One of the pleasing parts for me about this study was that the results, in a representative sample of smokers who had tried to quit, were almost perfectly consistent with the results we had previously published based on people trying to quit at our smokers clinic (Gandhi et al, 2009). Like our clinic study, this new paper found that the effect of menthol on inhibiting smoking cessation is a sizeable one. For example, among African Americans, while 62% of regular cigarette smokers successfully quit, only 44% of menthol smokers were able to quit. Also like our clinic study, the effect remained significant after controlling for differences in the relevant characteristics of those who smoke regulars and menthols. Also like our clinic study, the menthol effect differed between white (non-Hispanic) smokers and minority smokers. But one thing that was different was that Dr Gundersen’s study found that white menthol smokers were actually MORE likely to quit than white non-menthol smokers. So the question remains, why the difference of effect of menthol on quitting smoking between whites and minorities?
I remain convinced that the underlying mechanism of action of menthol is to enable smokers to inhale more nicotine (and smoke) under circumstances that require it. The main circumstance requiring the smoker to inhale more nicotine per cigarette is a situation forcing the smoker to reduce their daily cigarette consumption. There are various forces requiring smokers to reduce their cigarette consumption, but a major one is money. In recent times as cigarettes have become more expensive across the United States, many smokers can no longer afford to smoke a pack a day. So they have to reduce to 5 or 10 cigarettes per day or try to quit. Of course we know that as smokers reduce, they rend to inhale more nicotine per cigarette (an effect often referred to as “nicotine compensation”). But inhaling more smoke per cigarette can cause harsh sensations in the throat. Menthol cools that effect, making it easier for larger doses of the poison to go down (Williams et al, 2007). But one of the effects of inhaling a higher dose of nicotine per cigarette is that each cigarette becomes more reinforcing and addictive. Although there is always more than one explanation for any effect, I believe that facilitation of increased nicotine inhalation is one of the main effects of menthol. But people who have plenty of money don’t need to smoke fewer each day, and inhale more from each one. So there is a socioeconomic difference in the effect. This is part of the reason for the difference of effect of menthol in whites and minorities. In our clinic study we found a similar menthol effect in unemployed whites that we did in employed African Americans (with no effect of menthol on quitting at all in employed whites).
I suspect that if national data is analyzed focusing on unemployed white smokers living in the north east of the U.S. (the highest cigarette cost area), who tried to quit in recent times (when high cigarette taxes kicked in), we would find a lower quit rate among the menthol than the non-menthol smokers in that group.
In terms of harms to health, we’d more easily find these in the short term by looking, for example, at pregnancy outcomes in menthol versus non-menthol smokers. I’m suggesting greater study of the effects of menthol in pregnancy because it’s a situation when many smokers try to cut down or quit, but many remain smoking, and in which the health impact can be measured in the short term (e.g. birth weight and complications).
I’m leaving this conference with a greater clarity that menthol added to cigarettes make it easier for young people to start smoking and harder for smokers to quit, because menthol helps the poison go down easier.
Gundersen D, Delnevo C, Wackowski O. Exploring the relationship between race/ethnicity, menthol smoking, and cessation, in a nationally representative sample of adults. Preventive Medicine (2009), doi:10.1016/j.ypmed.2009.10.003
Gandhi KK, Foulds J, Steinberg MB, Lou SE, Williams J. Lower quit rates among menthol cigarette smokers at a tobacco treatment clinic. International Journal of Clinical Practice 2009 Mar;63(3):360-7.
Williams JM, Gandhi KK, Steinberg ML, Foulds J, Ziedonis DM, Benowitz NL. Higher nicotine and carbon monoxide levels in menthol cigarette smokers with and without schizophrenia. Nicotine Tob Res. 2007 Aug;9(8):873-81.