Do you smoke? Exercise? Use a cellphone?

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So many households now rely solely on cellphones that large health surveys conducted on land-line phones may no longer be capturing an accurate picture.

That’s according to a study released Wednesday by the Centers for Disease Control and Prevention --which conducts many of its own large health surveys by making random calls to land-line phones.

Oklahoma had the highest percentage of households with no land-line phones, at 26.2% , the CDC study found.

The states with the next highest rates of cellphone-only households were Utah (25.5%), Nebraska (23.2%), Arkansas (22.6%) and Idaho (22.1%).

Vermont, Connecticut, Delaware, South Dakota and Rhode Island were the states with the fewest households relying solely on cellphones. In Vermont, just 5.1% of households used cellphones only. In Rhode Island, 7.9% did.

In California, about 10% of households use only cellphones.

The study used data from 2007. Nationwide, more than 1 out of every 6 American homes -- 17.5% -- had only wireless telephones during the first half of 2008, the study found. That’s nearly 3% higher than 2007.

The information on cellphone usage came (ironically) from in-person interviews conducted by the CDC’s National Center for Health Statistics. Because its sample size was small, the study used Census Bureau population numbers and demographic data to estimate cellphone usage in all states.

In a 2006 study, author Stephen J. Blumberg of the CDC had found that adults without land-line telephones had greater odds of smoking and being uninsured, and lower odds of having diabetes, having a usual place for medical care and having received a flu shot in the last year.

Blumberg had concluded at the time that the number of households without land lines was too low to worry that excluding them would skew survey results.

But the new study shows not only that the percentage is growing but that it varies widely across regions and states.

Political pollsters and other researchers who conduct telephone surveys are, like the CDC, debating what to do about cellphones.

Some pollsters -- including the late, great Los Angeles Times poll -- got around the problem by hand-dialing randomly chosen telephone numbers from cellphone exchanges. Cell and land-line samples were combined and adjusted to estimates of household phone types, using the annual CDC survey.

-- Mary Engel

Lily Tomlin in a scene from ‘Rowan & Martin’s Laugh-In’ in 1973. Credit: Los Angeles Times file photo