Americans with disabilities smoke more than everyone else, according to the first national study to compare smoking rates between the two groups.

About one in four disabled people are smokers, compared to about one in five among the non-disabled, the U.S. Centers for Disease Control and Prevention reported Wednesday.

More people with disabilities also said they'd seen a doctor or nurse recently, and had been advised to quit cigarettes, the CDC study found.

Having such national data is helpful, but the results aren't surprising, said Kenneth Warner, a leading tobacco researcher who is dean of the University of Michigan School of Public Health.

The disabled population included people with mental illness and drug and alcohol addictions — groups known to have higher smoking rates. "It is very believable," Warner said, of the CDC study's findings.

More than 10 million Americans with disabilities smoke, according to the study authors.

They said many disabled people are smokers partly because a disproportionate percentage of them are low-income, and poor people have higher smoking rates. However, the study found that among people with lower incomes, disabled people smoked at a higher rate (37 percent) than non-disabled poor people (23 percent).

"We find that disability still matters," said Brian Armour, a CDC health economist who was the study's lead author.

The surprise was that disabled smokers more often reported getting medical advice to quit, although a substantial number said that advice didn't include specifics.

The nationwide study was done through a random-digit-dialed telephone survey in 2004 of about 294,000 U.S. adults.

The survey did not include people in institutions or people whose disability prevents them from answering the phone, so it's likely the disabled smoking rate is even higher.

Delaware had the highest smoking rate among people with disabilities, about 39 percent. The state also had the largest gap in smoking prevalence between disabled and non-disabled people, 17 percentage points. It's not clear why.