People who smoke a cigarette as soon as they wake up in the morning are more likely to develop lung and oral cancer than other smokers, a new study reveals.

Penn State researchers analyzed data from nearly 2,000 adult smokers who took part in the U.S. National Health and Nutrition Examination Survey. The participants provided blood samples and information about their smoking behavior.

The investigators found that about 32 percent of the participants smoked their first cigarette of the day within five minutes of waking. Among the others, 31 percent smoked within 6 to 30 minutes, 18 percent smoked within 31 to 60 minutes, and 19 percent smoked more than an hour after waking.

People who had a cigarette immediately after waking had higher levels of NNAL -- a byproduct of a tobacco-specific cancer-causing substance called NNK -- in their blood than those who smoked a half hour or more after waking, regardless of how many cigarettes they smoked in a day, the study authors reported.

The research team also found that NNAL levels in the participants' blood was also associated with factors such as their age, their gender, the age they started smoking, and whether or not another smoker lived in their home.

"Most importantly, we found that NNAL level was highest among people who smoked the soonest upon waking, regardless of the frequency of smoking and other factors that predict NNAL concentrations," study co-author Steven Branstetter, an assistant professor of biobehavioral health, said in a Penn State news release.

"We believe these people who smoke sooner after waking inhale more deeply and more thoroughly, which could explain the higher levels of NNAL in their blood, as well as their higher risk of developing oral or lung cancer," he added. "As a result, time to first cigarette might be an important factor in the identification of high-risk smokers and in the development of interventions targeted toward early morning smokers."