Smokers who light up first thing in the morning are at particularly high risk for cancer, study findings indicate.
Smokers who had their first cigarette within 30 minutes of waking had a 59% higher risk for head and neck cancers and 79% higher risk for lung cancer compared with those who waited at least an hour, Joshua E. Muscat, PhD, of the Department of Public Health Sciences at Penn State College of Medicine in Hershey, Penn., and colleagues found.
The risk was also elevated among smokers who lit up 31 minutes (42%) to 60 minutes (31%) after waking, the researchers reported online in Cancer.
Although the underlying mechanism that regulate time to first cigarette and cancer risk remain unclear, smoking earlier in the day may signal greater nicotine dependence, according to the researchers. “These findings may help to identify high-risk individuals who would benefit from targeted interventions,” they wrote.
Muscat and colleagues compared cancer risk between two separate cohorts. In the first study they analyzed data from 1,055 patients with head and neck cancers and 795 controls seen at New York-area academic center hospitals, all of who had a history of cigarette smoking.
After adjusting for the number of cigarettes smoked per day in this cohort, the researchers found that time to first cigarette independently predicted cancer risk — with those who smoked within 30 minutes of waking 2.11-fold more likely to develop head and neck cancers (95% CI: 1.61 to 2.77), and those who smoked 31 to 60 minutes after waking, 1.63-fold more likely (95% CI: 1.18 to 2.26).
In a separate analysis, the researchers looked at data from 4,775 newly diagnosed lung cancer cases and 2,835 controls, all former or current cigarette smokers, who were seen at the same group of academic hospitals.
After adjusting for the number of cigarettes smoked, the researchers found that earlier smoking was independently associated with lung cancer risk as well. Data indicated a 2.64-fold higher risk among smokers who lit up within 30 minutes of waking (95% CI: 2.31 to 3.02) and a 1.58-fold higher risk among those who smoked 31 to 60 minutes after waking (95% CI: 1.35 to 1.84).
Results were similar after the researchers stratified by years since quitting and current smoking status. The researchers noted that odds ratios were lower than those seen in earlier studies, in which control groups were composed of never smokers.
Study limitations include the small number of minority patients, which limits the generalizability of the findings, as well as the potential for recall bias, measurement error and confounding due to the case-control study design.
Muscat JE et al. “Nicotine dependence phenotype, time to first cigarette, and risk of head and neck cancer.” Cancer. 2011;doi:10.1002/cncr.26235.
Muscat JE et al. “Nicotine dependence phenotype and lung cancer risk.” Cancer. 2011;doi:10.1002/cncr.26236.