Once a smoker always a smoker, right? Not quite.

As the number of smokers drops, the remaining smokers actually smoke less and are more likely to quit, according to a study published Wednesday in the journal Tobacco Control.

It supports the idea that smoking in the United States is heading down a "softening" curve. That means more people are trying to quit, and the number of people quitting compared to smokers is increasing as the number of total smokers declines.

Over in Europe, the researchers found, things are slightly different. The percentage of smokers who have quit remained constant even as fewer people smoked, while the number of cigarettes smoked per day dropped, as it has in U.S.

The study is based on population data collected by the Census Bureau in the U.S. over 18 years, while six years' worth of public opinion surveys conducted by the European Commission were used for EU counterpart.

The researchers say their results bring into question the practice of harm reduction, a public health approach for tobacco control in use since the 1970s. Harm reduction was proposed as a way to minimize the exposure of smokers unable or unwilling to quit. More recently, e-cigarettes have been promoted as a replacement for the traditional cigarette.

"The fundamental thing is that harm reduction is wrong," says Dr. Stanton Glantz, senior author of the study and director of the Center of Tobacco Control Research and Education at the University of California, San Francisco. "It's not an irrational idea, but it's just not happening."

While Joanna Cohen, director of the Institute for Global Tobacco Control at Johns Hopkins Bloomberg School of Public Health, agrees that there's a 'softening' trend, she thinks that e-cigarettes and harm reduction policies are not a black-and-white issue.

"In tobacco control, those words carry a log of baggage right now," Cohen says. "Different experts have different opinions." There's no formal policy at the Centers for Disease Control and Prevention or other agencies that specifically has a harm reduction approach, she notees.

"Some people think that [e-cigarettes] are going to be the solution to the problem," she continues, "Other people are more concerned that either they won't make a difference or cause harm."

Potential problems include e-cigarettes preventing people from quitting smoking altogether and tempting new users, since they are marketed as not as harmful as the traditional cigarette. Evidence isn't clear either way at this point.

One reason for the shifting debate is that our attitudes and understanding have changed about nicotine, Glantz says.

People used to believe that nicotine kept people addicted to cigarettes but that it wasn't dangerous itself. The smoke was thought to be the source of harmful toxins. So the idea was to introduce new ways to deliver nicotine such as e-cigarettes that could give people the nicotine they desired but didn't involve burning tobacco.

Now we know better. The 2014 U.S. Surgeon General's report concluded that nicotine is addictive, that a high-enough dosage can be very toxic in a short amount of time, and that exposure to nicotine during pregnancy and childhood can have serious adverse consequences. E-cigarettes deliver nicotine and other chemicals to users, but in vapor instead of smoke.

The study results suggest that current tobacco control policies already in place are working. Glantz says. He and first author Margarete Kulik, a postdoctoral fellow at UCSF, attribute the general decline in smokers to this success, which includes the debut of clean indoor air laws that ban smoking inside workplaces, restaurants and other facilities. National media campaigns that aimed to de-normalize smoking and raised cigarette taxes also helped.

"It certainly suggests that we need to keep doing what we're doing," says Dr, Vaughan Rees, director of the Center for Global Tobacco Control at the Harvard T.H. Chan School of Public Health, who was not involved in this study.

Since current policies work and data suggests that remaining smokers are more likely to quit and smoke less, then there really is no need to promote new recreational nicotine products like e-cigarettes under the name of harm reduction, Glantz says.

Cohen also points out that there are challenges when you look at population-level data and think about what that means for policy.

A governmental institution such as the CDC might make use of the same data in a different way than the average physician will. If you have a hard-core smoker sitting in front of you, you as a health care provider want to help that person as best as you can. Maybe an e-cigarette is the best choice for that particular patient.

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