In March, New York City banned smoking in almost every indoor workplace, including restaurants and bars. The law was designed to protect employees from second-hand smoke, thought to contribute to lung cancer and heart disease in non-smokers.

This law is an acknowledgment that significant numbers of people smoke and put co-workers at risk.

The fact that so many adults still smoke (see chart) points out that certain prevention efforts may not be effective. For example, the efforts to stop teen-agers from starting to smoke may not keep them from starting as adults, according to Mailman School of Public Health researchers.

For years, many public health researchers have believed that smoking prevention programs should be aimed at teen-agers because those are the years when smokers usually take up the habit that remains with them into adulthood. But the Mailman researchers, while supportive of adolescent smoking prevention efforts, suggest that smoking prevention is more complicated than previously believed.

It was widely thought, for instance, that higher cigarette taxes might render cigarettes so expensive that teen-agers would never start smoking. Since most smokers start smoking as teens, this seemed like a logical way to end adult smoking as well. But in a paper in the March issue of the American Journal of Public Health, Dr. Sherry Glied, professor and chairwoman of health policy and management at Mailman, summarized her own and others' research that indicates that while higher tobacco taxes do indeed keep people from starting to smoke as teen-agers, the taxes may simply lead teens to postpone smoking initiation into adulthood.

Using data from a 15-year national youth survey that followed young people, ages 14 to 24, Dr. Glied found that while a 10 percent increase in cigarette taxes leads to about a 1 percent decline in adult smoking, taxes experienced during youth are almost entirely unrelated to adult smoking behavior.

The research that Dr. Glied summarized is based on a small number of studies and subjects but it raises the possibility that discouraging smoking among young people may not result in significant reductions in adult smoking rates, Dr. Glied says.

"If they are to have long-term effects, efforts to reduce smoking among teens need to be sustained into adulthood and should encompass changes in adult behavior rather than simply focusing on adolescent initiation," Dr. Glied says. "The increasing numbers of smokers who quit suggest that encouraging adult cessation, while difficult, may be at least as effective a long-term policy strategy as reducing teen-age initiation."

Meanwhile, the research of Dr. Joyce Moon Howard, assistant professor of sociomedical science at Mailman, adds another dimension to the issue. In a paper published in the same issue of the American Journal of Public Health, Dr. Moon Howard analyzed data from the 2000 National Health Interview Survey and found that African American women start smoking later than Caucasian women. The mean age of smoking onset for African American women in the survey was 19.28 years; Caucasian women began smoking at 18.21 years.

The survey showed that smoking rates also are higher for young Caucasian women at every age group until the mid-30s. For example, 28 percent of Caucasian women 18 to 20 years old reported that they currently smoked compared with 15 percent of African American women in that age group. However, by ages 41 to 43, more African American women (36 percent) than Caucasian women (28 percent) are smoking. The diverse contexts and environments that interact with psychological and physiological considerations to shape different trajectories to cigarette use need to be better understood to gap design effective prevention initiatives, Dr. Moon Howard says.

"Because African American women start smoking later, they are usually not directly targeted by teen smoking prevention programs, such as school-based efforts," says Dr. Moon Howard. "Smoking in early adulthood—the peak childbearing and child-raising years for women—carries health risks for the women and their children. Determining why adult women take up smoking and developing prevention and cessation interventions would greatly benefit women's health."