If you think smokers have a tougher time quitting these days, you're right — and genetics play a significant role, according to a study led by the University of Colorado at Boulder.

Researchers surveyed a database of nearly 600 pairs of twins — some identical, some fraternal — about their smoking patterns from 1960 to 1980, as social attitudes about smoking changed.

Among identical twins, if one quit, the other also quit within a two-year span 65 percent of the time, the study found. That happened only 55 percent of the time among fraternal twins.

Because identical twins share the same genes and fraternal twins don't, the statistically significant difference suggests a genetic factor influencing the ability to quit, said the study's co-author, CU sociology professor Fred Pampel.

"The main significance is that the population of smokers has changed substantially over time," he said. "And the approaches to eliminating smoking might have to change to deal with that. The genetic influences are stronger now than in the past, which means that they're harder-core smokers."

The study will appear in the November issue of the journal Demography. CU associate professor Jason Boardman and doctoral student Casey Blalock led the effort, which was co-authored with Pampel, Peter Hatemi of Penn State University, Andrew Heath of Washington University in St. Louis and Lindon Eaves of Medical College of Virginia.

Pampel explained that the bigger the statistical gap between the two groups of twins, the more influential the genetic component.


This study builds off earlier research that looked at a different data set — a cross-section of current smokers — to determine whether genetic or social factors contributed most to taking up the habit, said Boardman.

An increasing role

He added that in 1964, the year of the U.S. surgeon general's report warning of smoking's adverse health effects, there were virtually no genetic factors to predict whether one would become a smoker. But from that point on, genetics played an increasing role.

"If my argument is true," said Boardman, "then as you look over time at the composition of those who remain smokers, those people willing to pay $10 a pack and smoke in the freezing cold, these might be the most genetically vulnerable."

The demography studied confirmed that theory.

In the 1970s, as state and local governments began enacting laws and taxes designed to deter smoking, the population of smokers shifted.

Many simply quit as it became less socially acceptable and health hazards became more widely understood. Those who continued to smoke generally had a stronger attraction to the habit or a strong addiction to nicotine.

"Hard time quitting"

"Now," said Boardman, "(the population) is much more comprised of genetically sensitive persons who have a hard time quitting smoking."

The measures that proved effective at cutting smoking in past decades may be less so among today's smokers who face genetic hurdles, the researchers contend.

"The policies of higher taxes and restrictions have been very effective, but their benefits might be leveling off and new strategies might be needed," Pampel said, listing measures such as nicotine replacement therapy, counseling and other pharmaceuticals.

He noted that the study represents "just one way of approaching the issue." Initially, the researchers weren't looking to address public policy on smoking but rather were seeking to examine the interplay between genetics and social environments.

"Smoking," said Pampel, "seemed to be a good topic to use this on."

Kevin Simpson: 303-954-1739 or ksimpson@denverpost.com