Cigarette smoking in the U.S. hit another record low last year as more people attempted to quit, according to an annual study from the Centers for Disease Control and Prevention published Thursday.

Some 13.7% of U.S. adults, or 34.2 million people, said they smoked last year, according to the CDC's study analyzing data from the 2018 National Health Interview Survey. That's down slightly from 2017, though the change is not statistically significant. Use of tobacco products overall remained largely the same.

The findings present both good news and bad news, said Brian King, deputy director for research translation in the CDC's office on smoking and health. On one hand, cigarette smoking is at the lowest level since the CDC started measuring it in the 1960s, he said.

"On balance, over 34 million adults are smoking cigarettes, and we also have 50 million adults using some tobacco product," he said, noting that cigarette smoking disproportionately affects people with lower income and education levels, as well as minority groups and people with mental illnesses.

Cigarette smoking has plummeted more than two-thirds since officials started tracking it in 1965. Yet smoking remains the leading cause of preventable death in the U.S., killing about 480,000 Americans every year, according to the CDC. More smokers are attempting to quit and are quitting successfully, according to this year's study.

Use of e-cigarettes among adults increased to 3.2% in 2018 from 2.8% in 2017. These products are billed as a less harmful alternative for people to consume nicotine. The data does not reveal whether e-cigarette users are former smokers who have switched.

King cautioned that young adults drove the increase. Use of e-cigarettes was the highest among adults between the ages of 18 and 24, with 7.6% of respondents in this age group saying they vape.

"What we don't want to be doing is playing a game of public health whack-a-mole where we let the use of some products go up while others go down, particularly among the young adult population," King said.