The pattern of results from studies examining the association between mentholated cigarette smoking and smoking cessation is mixed. However, there does appear to be broadly consistent evidence that menthol smoking is more prevalent in racial/ethnic minority populations and that menthol smokers tend to smoke fewer cigarettes per day than regular cigarette smokers (e.g., Giovino et al., 2004
and most studies in ). There are also trends suggesting that the association between smoking menthol cigarettes and greater difficulty quitting is stronger in (a) racial/ethnic minority populations, (b) younger smokers, and (c) after the year 1999, as opposed to the 1980s.
One possibility, consistent with this pattern of results, is that the effect of menthol on quitting smoking is only apparent in circumstances where the smoker has been forced to reduce their cigarette consumption, with the most obvious influence being socioeconomic factors. The price of cigarettes has increased in many parts of the United States since the 1990s. Young smokers, and racial/ethnic minority smokers tend to be less affluent and are thus more affected by the increased prices, forcing them to consume fewer cigarettes per day (as is found in most studies in these groups). One possible mechanism explaining the menthol effect is that these smokers may increase their total nicotine intake per cigarette to obtain their preferred dose of nicotine from fewer cigarettes. The menthol effect on cessation may stem from the cooling effects of menthol facilitating such “compensatory” smoking and allowing these smokers to obtain a larger and perhaps more reinforcing nicotine “hit” per cigarette. There is some evidence that smokers of menthol cigarettes tend to obtain higher levels of carbon monoxide (CO), nicotine, and cotinine per cigarette smoked (Clark, Gautam, & Gerson, 1996
; Ahijevych & Parsley, 1999
; Benowitz, Herrera, & Jacob, 2004
; Perez-Stable, Herrera, Jacob, & Benowitz, 1998
; Williams et al., 2007
). Gandhi et al. (2009)
reported that the association between menthol smoking and lower quit rates was stronger among unemployed than full-time employed smokers, regardless of race/ethnicity, which is consistent with the model proposed above.
Adolescent smokers are a group that could be particularly sensitive to the menthol effect mechanism being proposed here as their cigarette consumption is often restricted by parental/school/legal rules as well as by financial constraints. There are no studies comparing quit rates between adolescent menthol and nonmenthol smokers. However national surveys of adolescent smokers that included indirect measures of dependence have consistently found that menthol smokers, compared to nonmenthol smokers, are significantly more likely to smoke within an hour of waking and that menthol smokers are more likely than nonmenthol smokers to experience cravings after not smoking for a few hours (Hersey et al., 2006
; Wackowski & Delnevo, 2007
Ahijevych, Weed, and Clarke (2004)
conducted an experimental test of the theory that menthol enables smokers to inhale more nicotine per cigarette when forced to reduce daily cigarette consumption. This study examined smoking behavior in 25 women (13 African American) while they resided at a research center for 6 days and were given access to either: (a) their usual number of cigarettes, (b) cigarettes restricted to 50% of normal, or (c) 167% of their normal consumption. In this study, all 13 of the African American women smoked menthols, as did a third of the white women. There were significantly higher percentage increases in exhaled CO levels among menthol smokers compared to nonmenthol smokers in the increased and restricted conditions. Also, African American menthol smokers had significantly higher percentage increases in exhaled CO compared with white menthol smokers in the restricted condition. This study also identified “efficient smokers” by their high baseline cotinine/cigarette ratio and found that their nicotine intake per cigarette increased even more in the “restricted” condition. Specifically, the pre-post cigarette “boost” in blood nicotine went up from 32 to 47 ng/ml. The typical blood nicotine boost from smoking a cigarette is about 10–15 ng/ml (Foulds et al., 1992
; Patterson et al., 2003
). All but one of these “efficient” smokers were menthol smokers. The data from this study are consistent with the theory that menthol smokers increase their smoke (CO and nicotine) intake per cigarette more than nonmenthol smokers when access to cigarettes is restricted. It may be that the large rapid increases in blood nicotine concentration resulting from this more “efficient” style of smoking (blood nicotine boost of 47 ng/ml per cigarette in the the study by Ahijevych et al., 2004
) produces more reinforcement per cigarette and consequently greater difficulty quitting.
This hypothetical model explaining how menthol may influence smoking cessation needs to be evaluated in further studies. If true, one might expect the putative menthol effect on cessation to become stronger over time as cigarette prices and smoking restrictions have increased dramatically since the beginning of the 21st century and when the United States is in a period of economic recession.
Other factors may also be involved. For example, there is evidence that menthol may itself inhibit nicotine metabolism, causing greater nicotine exposure per unit inhaled (Benowitz et al., 2004
). In addition, the studies to date have mainly assumed that the only factor that differs between the brands being smoked is the mentholation. In reality, each cigarette sub-brand can vary on a number of additional dimensions, including filter ventilation, standardized machine-measured nicotine yield, and cigarette length. It has been noted that a very high proportion of African American smokers smoke specific brands (e.g., Newport) with little filter ventilation, and relatively high machine-measured nicotine yield, whereas whites tend to smoke ventilated low or medium machine-measured nicotine yield cigarettes such as Marlboro/Marlboro Lights (Melikian, Djordjevic, Chen, & Richie 2007
; Okuyemi, Ebersole-Robinson, Nazir, & Ahluwalia, 2004
). Rose and Behm (2010)
recently presented the reanalyses of two clinical trials examining the association between abstinence, menthol preference, and various other variables. They found that among menthol smokers, preference for higher nicotine-yield cigarettes was strongly related to lower socioeconomic status and that this mediated the link between menthol smoking and low quit rates (6-month point abstinence among menthol smokers of high yield cigarettes = 11% as compared with 26% for high yield nonmenthol smokers, p
= .005 when adjusting for other covariates). They also found significantly higher baseline cotinine per cigarette in menthol versus nonmenthol smokers.
Consistent with Rose and Behm’s (2010)
findings, Farrelly, Loomis, and Mann (2007)
found that over the years 1994–2004, U.S. inflation-adjusted cigarette prices increased by over 50%, and this was associated with increased consumption of higher machine-measured nicotine yield cigarettes, with this effect being larger for menthol versus nonmenthol cigarettes. This data, derived from analyses of over 800,000 cigarette purchases at U.S. supermarkets, is consistent with the idea that as cigarette prices increase, menthol cigarettes are particularly consumed in a manner that facilitates greater nicotine absorption per cigarette.
It should be noted that most of the studies to date have not been designed specifically to evaluate the effects of menthol on cessation, and even the relatively large studies (e.g., Hyland et al., 2002
and Murray et al., 2007
) suffered from a lack of statistical power to detect within-race effects, partly because such a low proportion of African Americans smoke nonmenthol brands. Future analyses of existing and ongoing national survey datasets (e.g. National Health Interview Survey, National Health And Nutrition Examination Survey) may help clarify this issue. Where possible, such analyses should include an assessment of the effects of socioeconomic status (via measures of income, financial assets, employment status, and education), nicotine/smoke intake (e.g., via biomarkers such as CO and cotinine), and also indicators of cigarette price (which can be estimated from the person's home state and preferred brand). Future studies should collect adequate measurement of cigarette brand and sub-brand smoked (including whether it is a menthol brand), brand switching, the socioeconomic status of participants, and their biomarker concentrations. This is also true for clinical trials not necessarily designed to assess the effects of menthol on cessation.
In conclusion, research to date finds little evidence of an association between menthol cigarette smoking and increased difficulty quitting among middle-aged (and older) white smokers. However, recent studies have consistently found that racial/ethnic minority smokers of menthol cigarettes have a lower quit rate than comparable smokers of regular cigarettes, particularly among younger smokers. This pattern of results is consistent with an effect that relies on menthol to facilitate increased nicotine intake from fewer cigarettes where economic pressures restrict the number of cigarettes smokers can afford to purchase.