(December 2011) Today's smokers are more strongly influenced by genetic factors than in the past, and that influence makes it more difficult for them to quit, according to a new study of twins published in the December issue of the journal Demography.1

"In the past, when smoking rates were higher, people smoked for a variety of reasons," says Fred Pampel, a Colorado University-Boulder researcher and study co-author. "Today the composition of the smoking population has changed. Smokers are more likely to be hard-core users who are most strongly influenced by genetic factors."

The study shows that adult identical twins sharing a common genetic structure are significantly more likely to quit smoking at the same time than are fraternal twins who do not share identical genes. This genetic influence has increased in importance among smokers following the initial restrictive legislation on smoking enacted in the United States in the 1970s, Pampel reports.

The U.S. Centers for Disease Control and Prevention report that in 2009 about 21 percent of U.S. adults ages 18 and older were current smokers, while an additional 21 percent were former smokers.2 More than one-half of the U.S. adult population (58 percent) report never having smoked more than 100 cigarettes in their lives. "These days people don't smoke as much for social reasons," he says. "They in fact face criticism for the habit but tend to smoke because of their dependence on nicotine."

The researchers examined the smoking patterns of 596 pairs of twins, 363 of them identical and 233 of them fraternal. They focused on smoking patterns from 1960 to 1980, a time when public attitudes toward smoking shifted.

Among identical twins, 65 percent of both twins quit during a two-year timeframe if one twin quit, but among fraternal twins, the percentage dropped to 55 percent, a statistically significant difference that indicates a genetic component at work, Pampel explains. While a specific genetic marker has been hard to identify among those who smoke, certain genetic similarities can be inferred.

The study has implications for current public policies aimed at reducing smoking, policies that may be becoming less effective. Since restrictive anti-smoking legislation began to be enacted in the United States in the 1970s, many smokers have quit. "Prior to 1975 this (potentially genetic) pattern wasn't clear because there were so many smokers."

Two of today's main anti-smoking policies include heavy taxes on cigarettes and vast reductions in the number of public spaces where smoking is allowed, particularly in bars and restaurants. But with indications that the genetic component is growing, it may be time to treat smoking more like an addiction than a choice, Pampel argues. Such a policy shift might include more emphasis on nicotine-replacement therapy and counseling.

Additional study authors include Jason Boardman and Casey Blalock of Colorado University-Boulder, Peter Hatemi of Pennsylvania State University, Andrew Heath of Washington University in St. Louis, and Lindon Eaves of the Medical College of Virginia.


References

  1. Jason Boardman et al., "Population Composition, Public Policy, and the Genetics of Smoking," Demography 48, no. 4 (2011), accessed at www.springerlink.com/content/dj72214072562181/fulltext.pdf, on Nov. 29, 2011.
  2. National Center for Health Statistics, "Summary Health Statistics for U.S. Adults: National Health Interview Survey, 2009," Vital and Health Statistics 10, no. 249 (2010), accessed at www.cdc.gov/nchs/data/series/sr_10/sr10_249.pdf, on Nov. 29, 2011.