Statistics released today show a growing number of U.S. smokers are not lighting up as often, but federal officials say cutting back without quitting is just as dangerous as not quitting at all.

A comparison of annual state surveys conducted from 1996 to 2001 shows that while the percentage of smokers remained steady, the number who said they smoked only occasionally rose in 38 states and the District of Columbia.

Analysts with the Centers for Disease Control and Prevention point to increased cigarette prices, higher taxes and smoking bans in public areas as likely reasons people are lighting up less frequently.

"This is still a phenomenon that we don't fully understand," said Terry Pechacek, associate director for science for the CDC's Office for Smoking and Health. "When it was first picked up in the 1980s, it was discounted in the public health community as an almost aberrant phenomenon. It was almost unusual for someone not to be a daily smoker."

The annual phone survey asked adults, "Have you smoked at least 100 cigarettes in your entire life?" and "Do you now smoke cigarettes every day, some days, or not at all?"

Among the 50 states and the District, the study found that the median rate in 2001 of those who had smoked at least 100 cigarettes and said they smoked either every day or some days was 23.4 percent, and the median rate of those smokers who said they smoked only some days was 24 percent.

Among the states showing an increase in the number of occasional smokers, Arizona went from 16.2 percent in 1996 to 28 percent in 2001; Delaware, 13.5 percent to 24 percent; Nevada, 10.8 percent to 22.8 percent, and Ohio, 9.6 percent to 20.8 percent. The District had the highest percentage of smokers who said they smoked only occasionally, at 41.2 percent.

Reducing tobacco use by half or more without quitting "did not decrease mortality rates from tobacco-related diseases compared with" heavy smokers of 15 or more cigarettes a day, a recent study found.