Smoking soon after waking may increase cancer risk

The sooner a person smokes a cigarette upon waking in the morning, the more likely he or she is to acquire lung or oral cancer, according to Penn State researchers in a study published in Cancer Epidemiology, Biomarkers & Prevention (March 29, 2013).

"We found that smokers who consume cigarettes immediately after waking have higher levels of NNAL -- a metabolite of the tobacco-specific carcinogen NNK -- in their blood than smokers who refrain from smoking a half hour or more after waking, regardless of how many cigarettes they smoke per day," explained Steven Branstetter, PhD, assistant professor of biobehavioral health, in a university release.

Levels of NNAL, or 4-(methylnitrosamnino)-1-(3-pyridyl)-1-butanol, in the blood can predict lung cancer risk in rodents as well as in humans, according to Branstetter. In addition, NNAL levels are stable in smokers over time, and a single measurement can accurately reflect an individual's exposure.

The researchers examined data on 1,945 adult participants who smoke from the National Health and Nutrition Examination Survey who had provided urine samples for analysis of NNAL. These participants had also provided information about their smoking behavior, including how soon they typically smoked after waking.

Branstetter and co-author Joshua Muscat, PhD, found that approximately 32% of the participants smoked their first cigarette of the day within five minutes of waking. Thirty-one percent smoked within six to 30 minutes of waking, 18% smoked within 31 to 60 minutes of waking, and 19% smoked more than one hour after waking. In addition, NNAL level in the participants' blood was correlated with the participants' age, the age they started smoking, their gender, and whether or not another smoker lived in their home, among other factors.

NNAL level was highest among those who smoked the soonest upon waking, regardless of smoking frequency or other factors that predict NNAL concentrations, according to Branstetter. Inhaling more deeply and more thoroughly could explain the higher levels of NNAL in their blood, as well as their higher risk of developing oral or lung cancer.

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