It seems intuitive when you think about it -- those who must smoke the quickest after waking, are likely the most addicted to cigarettes.  And smokers who are most addicted, likely use more cigarettes on average, and thus have a higher cancer risk.

This straightforward hypothesis has been upheld in a pair of studies [1][2] currently previewed in the journal Cancer.  Penn State University College of Medicine researcher Joshua E. Muscat, Ph.D, was the lead author on both studies.

The first study surveyed 4,776 smokers with lung cancer, and 2,835 smokers without lung cancer (7,611 total smokers).  It found that those who smoked within half an hour of waking up were 80 percent more likely to have lung cancer than those who waited an hour.  Those who waited between 30 and 60 minutes were 30 percent more likely than those who waited a full hour.

The second study told a similar tale when it came to neck and throat cancers.  Those smoking between within 30 minutes of waking were 60 percent more likely, and those who smoked within 31-60 minutes were 40 percent more likely to develop these cancers than those waited more than an hour.

Based on these results, one would expect early morning consumption to also be linked to other tobacco-related ailments, such as brain damage.

Dr. Joshua Muscat suggested the possible link between level addiction and how quickly one had to indulge in a morning smoke, stating, "These smokers have higher levels of nicotine and possibly other tobacco toxins in their body, and they may be more addicted than smokers who refrain from smoking for a half hour or more."

Nicotine, the primary addictive chemical in tobacco smoke, has a half life of 2 hours in the body, meaning half of its dose is metabolically consumed within two hours of intake via inhalation.  Thus by six hours a mere 12.5 percent of the previous evening's dose remains, and by eight hours, only 6.25 percent, assuming the smoker lit up just before bed.

Despite the seemingly intuitive nature of this line of reasoning, the study authors, include Muscat emphasize caution, writing, "It is uncertain what explanation there is for the relationship."

Ultimately, the reason for the trend may be less important than the trend itself.  By identifying a high-risk subgroup within smokers, doctors have a new, target to focus their most concerted smoking cessation efforts on. 

Smoking and cancer were first linked by studies in the 1950s, but smoking was not categorized as a physiological and psychological addiction by the American Psychiatric Association until 1980.