清晨吸烟增加患肺癌、头颈癌几率

Two new studies have found that smokers who tend to take their first cigarette soon after they wake up in the morning may have a higher risk of developing lung and head and neck cancers than smokers who refrain from（克制，抑制） lighting up right away. Published early online in Cancer, a peer-reviewed journal of the American Cancer Society, the results may help identify smokers who have an especially high risk of developing cancer and would benefit from targeted smoking interventions to reduce their risk. Cigarette smoking increases one's likelihood of developing various types of cancers. But why do only some smokers get cancer? Joshua Muscat, PhD, of the Penn State College of Medicine in Hershey, and his colleagues investigated whether nicotine dependence as characterized by the time to first cigarette after waking affects smokers' risk of lung and head and neck cancers independent of cigarette smoking frequency and duration.

The lung cancer analysis included 4,775 lung cancer cases and 2,835 controls, all of whom were regular cigarette smokers. Compared with individuals who smoked more than 60 minutes after waking, individuals who smoked 31 to 60 minutes after waking were 1.31 times as likely to develop lung cancer, and those who smoked within 30 minutes were 1.79 times as likely to develop lung cancer.

The head and neck cancer analysis included 1,055 head and neck cancer cases and 795 controls, all with a history of cigarette smoking. Compared with individuals who smoked more than 60 minutes after waking, individuals who smoked 31 to 60 minutes after waking were 1.42 times as likely to develop head and neck cancer, and those who smoked within 30 minutes were 1.59 times as likely to develop head and neck cancer.

These findings indicate that the need to smoke right after waking in the morning may increase smokers' likelihood of getting cancer. "These smokers have higher levels of nicotine and possibly other tobacco toxins（毒素） in their body, and they may be more addicted than smokers who refrain from smoking for a half hour or more," said Dr. Muscat. "It may be a combination of genetic and personal factors that cause a higher dependence to nicotine."

According to the authors, because smokers who light up first thing in the morning are a group that is at high risk of developing cancer, they would benefit from targeted smoking cessation（停止，中断） programs. Such interventions could help reduce tobacco's negative health effects as well as the costs associated with its use.