Since the mid-1960s, the percentage of adult Americans who smoke has declined dramatically, in part because of tobacco taxes and other government policies aimed at discouraging smoking. But after declining steadily from about 50 percent in the mid-1960s to about 20 percent in the early 1990s, smoking rates have largely plateaued, seemingly unresponsive to public policy initiatives.
A new study by Robert Wood Johnson Foundation (RWJF) Health & Society Scholar Jason Fletcher, PhD, MS, suggests that the explanation may be in smokers’ genes.
In a December 2012 article in PLOS One, Fletcher notes the apparent failure of tobacco taxes to drive certain smokers away from the habit and focuses instead on a specific genetic characteristic, found in a nicotine receptor expressed in the brain and elsewhere. When nicotine reaches the receptor, it triggers the release of a pleasure reaction in the smoker. The genetic trait is expressed in one of three combinations, or genotypes, labeled by scientists as “C/C,” “C/G,” or “G/G.” Approximately 51 percent of Americans have the G/G genotype, while the remaining 49 percent have either the C/C or C/G genotype.
Fletcher analyzed genetic data from the National Health and Nutrition Examination Survey, conducted in the early 1990s—the most recent data compiled—along with state taxation rates. He found that individuals with the G/G genotype were less likely to continue smoking as tobacco taxes went up, while those with the C/C or C/G genotype were largely unaffected by such deterrents.
Fletcher writes that the genetic analysis helps explain the plateauing of smoking rates, and that it has implications for future policy choices:
This study showed that the impact of tobacco taxation on tobacco use is moderated by individual genotype. Indeed, only individuals with the protective G/G genotype were found to respond to state level tobacco taxation rates, suggesting an important clue in understanding why the rates of tobacco use among US adults have remained stubbornly persistent during a time period of large changes in tobacco control policies during the past two decades….
The results are stark in that a single [genetic combination] is used to completely segment the population into the approximately 50 percent of adults who are likely to respond to tobacco taxation and the 50 percent who are unresponsive. This is an important first step in future health policy efforts to further reduce adult smoking rates. Additionally, this study has begun a new examination … that may have broad scope in learning why some policies are effective and others are not, and also deepen our understanding of the genetic response to broad-based policy interventions.
Fletcher stops short of saying that the C/G or C/C genotypes cause particular smokers to be more easily or more strongly addicted. However, he says the data indicate that the genotypes, by whatever mechanism, are associated with a willingness to pay more money to satisfy a smoking habit.
Public Policy Implications
Fletcher says his findings suggest that while taxes and other such measures appear to be effective with some smokers, different public policies might be needed to help break C/G and C/C smokers of their habit. “The policies put in place between the 1960s and now have been responsible for a huge reduction in tobacco use. But we’ve plateaued, and have been at about 20 to 25 percent of the population for a couple decades. That suggests it might be time for additional policies.”
As Fletcher observes, the stakes are high from a public health point of view. “Tobacco use is among the most important causes of morbidity and the leading preventable cause of death in the United States,” he writes, “with over 400,000 deaths per year…more deaths than AIDS, alcohol use, cocaine use, heroin use, homicides, suicides, motor vehicle crashes and fires combined.” Recognizing the role that the various genotypes play could prompt policy-makers to tailor approaches that are effective not just with the smokers or would-be smokers with the G/G genotype, but also those with the C/G and C/C genotypes.
“Taxes aren’t the silver bullet,” Fletcher says, because raising them only decreases consumption among half of the smoking population. But pharmacological approaches might be available, he explains. “Some drugs operate on the receptors in question, and disrupt the process by which smokers enjoy nicotine. That might be one way to reach people you can’t reach with taxes. And you might use the revenue from smoking taxes to subsidize those drugs.”
Before such policy measures are considered, Fletcher says more research is needed—first to verify his findings, and then to explore more recent trends.
“One limitation with the data I used is that it’s from the early 1990s,” he says, because that’s all that is available. “Since then, tax rates have gone up further, and there have been new smoking bans and other ‘clean air’ laws. New data could tell us if those laws have had an impact” on smokers in the C/C and C/G groups.