Updated

Nearly 70 percent of U.S. adults who smoke say they want to quit, and more than half have tried in the past year, but only about six percent succeeded, U.S. health officials said Thursday.

Overall, about 20 percent of U.S. adults, or about 45.3 million people, still smoke, while 48.3 percent of smokers have been advised by their doctors to quit, according to the U.S. Centers for Disease Control and Prevention.

Smoking rates in the country are falling, but CDC officials are worried by signs that the pace of decline has slowed and are ramping up efforts to help smokers who want to quit.

According to the CDC's Morbidity and Mortality Weekly Report, only 32 percent of smokers who want to quit used any smoking cessation aid, such as nicotine patches or counseling.

"There is significant room for improving in this area. Use of these treatments can double or triple success rates," Dr. Timothy McAfee, director of the CDC's Office on Smoking and Health told a news briefing.

McAfee said education was also a big factor in a smoker's success at quitting. The study found that only 3.2 percent of those with less than a high school education who tried to quit succeeded, while 11.4 percent of those with a college degree who tried to quit succeeded.

There was also a big gap among blacks between their desire to quit and their success rate, he said.

McAfee said blacks had the highest interest among any group in intention to quit smoking, but they had the lowest success rate, at 3.3 percent. They were least likely to use counseling or medication.

He said one possible reason is that blacks are three times more likely than whites to use cigarettes flavored with menthol, which masks the burn of smoking. Among black smokers, 76.7 percent said they smoked menthol cigarettes, compared with 23.6 percent of whites.

A recent report by the Tobacco Product Scientific Advisory Committee to the U.S. Food and Drug Administration found that menthol flavoring in cigarettes decreases the likelihood of successful quitting.

The CDC study also found that having health insurance was a big factor in a person's ability to successfully quit smoking, as it meant they were more likely to be counseled by a doctor and to get reimbursed for nicotine patches or other aids.

According to the study, the uninsured had the lowest success rate of just 3.6 percent, while those with private insurance had a higher rate of 7.8 percent and people with military insurance had a success rate of over 9 percent.

Despite slowing quit rates, the study shows that many smokers want to kick the habit. McAfee noted that just five years ago, some health policymakers feared that aggressive anti-smoking campaigns could just harden the resolve of smokers to stick to their cigarettes.

"What this study shows is quite the opposite," he said. "It was reassuring to us."