New data show adults are less likely to smoke now than they were 10 years ago, although tobacco use still remains the biggest preventable cause of cancer and death in the country.

Centers for Disease Control and Prevention data show that the rate of cigarette smoking among U.S. adults declined from 20.9 percent (45.1 million) in 2005 to 15.1 percent (36.5 million) in 2015.

The CDC said the 2015 smoking level is the lowest since CDC began collecting data in 1965.

Agency officials pegged the decrease to investments in cancer control programs and a focus on reducing cancer, detecting it early and working to improve survival rates.

"Comprehensive tobacco control programs coordinate efforts to implement proven strategies to prevent tobacco use initiation among youth and young adults, to promote tobacco users to quit, to eliminate second-hand smoke exposure and to identify and eliminate tobacco-related disparities," CDC said.

However, the agency noted that the declines weren't universal across the U.S.

For instance, the Northeast region of the country has the highest smoking rate of 202 per 100,000 people, compared to the West that has 170 per 100,000.

The CDC found that each year from 2009 to 2013, about 660,000 people in the U.S. were diagnosed with cancer related to tobacco use and another 343,000 people died from it.

Currently, there are 12 types of cancer that are caused by tobacco use, but lung and colon cancer are the most common.