People who smoke their first cigarette within minutes after waking up have much higher levels of cotinine, a by-product of nicotine when processed by the body, than those who wait to smoke, regardless of the number of cigarettes smoked.
"Since cotinine levels appear to reflect the risk of lung cancer, our results suggest that smokers who smoke immediately after waking may be especially at risk for lung cancer," said researcher Joshua E. Muscat, Ph.D., M.P.H., professor of public health sciences at Penn State College of Medicine. "These people may require a more intensive intervention than other smokers to help them quit smoking on a sustained or permanent basis."
Results of this study are published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, as part of a special tobacco focus in the December issue.
Nicotine levels in the blood can be measured biochemically by the concentration of the metabolite cotinine. Muscat, along with John P. Richie, Jr., Ph.D., professor of public health sciences and pharmacology at Penn State College of Medicine, and colleagues conducted a community-based study in Westchester County, N.Y., to examine whether a behavioral aspect of nicotine dependence (the amount of time to the first cigarette after waking up) affects the physiological uptake of nicotine. This in turn may affect one's success in quitting smoking and have multiple health effects, such as lung cancer.
The study included 252 healthy black and white people who were daily cigarette smokers. Researchers examined a number of behavioral factors that are thought to measure the urge to smoke, and results showed a clear trend between lighting-up earlier and higher cotinine levels.
Cotinine levels varied from 16 ng/mL to 1180 ng/mL -- a 74-fold difference, according to the study. Participants who waited 30 minutes or more were categorized into the "low" dependant phenotype; those who smoked within the first 30 minutes of waking were considered "high." Number of cigarettes smoked per day and its association with cotinine levels varied as well.
"Not all smokers are the same and approaches to smoking reduction may need to account for individual smoking behaviors such as the intensity and frequency of puffing, cravings and physiological symptoms," said Muscat. "It is unclear why smokers who take their first puff immediately after waking have higher cotinine levels, but this may reflect a more intense pattern of smoking. We need to find out why this is."
The researchers are currently conducting follow-up studies to investigate levels of additional nicotine metabolites that will further confirm this association and help determine the impact of time to first cigarette as a novel risk factor for lung cancer.
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