Dr. Rostron first examined the Cancer Control Supplement of the 1987 National Health Interview Survey. Of 6,073 current smokers, 1,417 reported that they smoked menthol cigarettes and 3,690 were nonmenthol smokers (the menthol preference for the other 966 smokers was undetermined). Using a computerized mortality file developed specifically for these survey participants, Dr. Rostron then determined how many smokers died from lung cancer over the next 20 years, through 2006. Comparisons were made using hazard ratios (HRs), which can be interpreted similarly to relative risks.
Compared with nonmenthol smokers, menthol smokers age 50+ years had a significantly lower risk of dying from lung cancer (HR = 0.59, 95% Confidence Interval, CI = 0.37 – 0.95). The lower risk for menthol smokers was also seen at all ages (HR = 0.69), in both men and women (HR = 0.71 and 0.70 respectively), and especially in blacks (HR = 0.41). This indicates that the results were consistent across many smaller subgroups of smokers, although the HRs were not significant because of the smaller numbers.
Dr. Rostron’s results were in agreement with two previous epidemiologic studies. The first, published last year by Vanderbilt University’s William Blot and colleagues (abstract here), found that the incidence of lung cancer among menthol smokers was 65% of that among nonmenthol smokers (CI = 0.47 – 0.90).
The second study, published in 2003 by Steven Stellman at the American Health Foundation along with investigators at several other research institutions, also found that menthol smokers had lower lung cancer risk than nonmenthol smokers (abstract here). Dr. Stellman’s conclusion that “Smokers of menthol flavored cigarettes were at no greater risk for lung cancer than were smokers of unflavored brands” was a gross understatement. His data show that white men and white and black women who smoked menthols all had lower lung cancer risks than nonmenthol smokers. While the lower risks were not statistically significant for any subgroup, the odds ratio for all menthol smokers was 0.68, which is perfectly consistent with Dr. Rostron’s findings. It was highly unconventional for Dr. Stellman not to report that result.
It is interesting to consider these findings when reading last year’s FDA Tobacco Products Scientific Advisory Committee (TPSAC) report on menthol (available here). It appears that TPSAC deliberately downplayed the Blot lung cancer findings, while discussing other findings in detail. The Stellman study was not even mentioned.
In his new article, Dr. Rostron writes, “The reasons for [lower lung cancer risks among menthol smokers] are not clear at the present time.” There is little evidence that menthol smokers have higher quit rates than nonmenthol smokers. Dr. Rostron suggests that the mortality differences “may be due in part to differences in inhalation caused by product design and not necessarily to menthol itself.”
Does this mean that menthol cigarettes carry reduced risk? Dr. Rostron notes, “Smoking of any kind of cigarette is known to profoundly harm individual and population health…”, but he suggests that further research on menthol cigarettes “could potentially identify ways to decrease the individual risk of cigarettes.”
The importance of this newest research should not be underestimated. Last year, FDA Commissioner Margaret Hamburg emphasized that “Science underlies everything we do at this agency…” (here). Dr. Rostron and the Center for Tobacco Products should be commended for producing this analysis. One hopes it will be used appropriately by the FDA in development of science-based tobacco regulation.