People who are uninsured or on Medicaid are more than twice as likely to smoke tobacco compared to those covered by other insurance, according to a national study by the Centers for Disease Control and Prevention. About 28 percent of uninsured adults and 29 percent of adults on Medicaid smoke nationwide, according to the Centers for Disease Control and Prevention (CDC), compared with just 13 percent of adults on private insurance plans and 12.5 percent on Medicare. The CDC, which examined data from the 2014 National Health Interview Survey, published the findings in November. The CDC found that cigarette-smoking rates were higher among people who live below the poverty level (26.3 percent) and people with a GED certificate (40 percent). Overall, the prevalence of cigarette smoking among adults declined from 20.9 percent to 16.8 percent from 2005 to 2014, according to the CDC.