Time to first cigarette and upper aerodigestive tract cancer risk in Japan

Background: Cigarette smoking is the major cause for upper aerodigestive tract (UADT) cancers. The time to first cigarette (TTFC) of the day is a distinct indicator of nicotine dependence, but scanty information is available on its possible relation with UADT cancers (oral, oropharyngeal, hypopharyngeal, laryngeal, nasopharyngeal, and esophageal cancers). Methods: This case-control study includes a total of 1,009 incident UADT cancer cases and 3,027 age- and sex-matched noncancer controls admitted to the Aichi Cancer Center (Nagoya, Japan) between 2001 and 2005. We estimated OR and 95% confidence intervals (CI) for TTFC using logistic regression models after adjustment for several potential confounders. Results: TTFC was inversely related to the risk of UADT cancer, and this association was consistent across subtypes of head and neck cancer and esophageal cancer. For all UADT cancers considered among ever smokers and after accurate allowance for smoking quantity and duration, besides other relevant covariates, compared with TTFC more than 60 minutes, the adjusted ORs were 1.40 (95% CI: 0.93-2.11) for 31 to 60 minutes, 1.76 (95% CI: 1.20-2.58) for 6 to 30 minutes, and 2.43 (95% CI: 1.64-3.61) for within 5 minutes. No significant heterogeneity was found in strata of sex, age, alcohol consumption, fruit and vegetable intake, and occupation for overall and site-specific analysis. Conclusion: Nicotine dependence, as indicated by the TTFC, is associated with increased risk of UADT cancers and is therefore an independent marker of exposure to smoking. Impact: Our result indicates more detailed risk evaluation of UADT cancers that is enabled by the TTFC.