Time to First Cigarette, a Proxy of Nicotine Dependence, Increases the Risk of Pulmonary Impairment, Independently of Current and Lifetime Smoking Behavior.

INTRODUCTION: Cigarette smoking is the largest known risk factor for chronic obstructive pulmonary disease (COPD), but little is known about the role of time to first cigarette (TTFC), an indicator of nicotine dependence (ND). This study examines whether daily TTFC is associated with pulmonary outcomes, independently of smoking behavior.

METHODS: A cross-sectional sample of 1461 current adult smokers were drawn from the National Health and Nutrition Examination Survey (NHANES), 2007-2010. The relationships of daily TTFC with outcomes of spirometry-defined pulmonary impairment and self-reported respiratory symptoms (coughing, bringing up phlegm, and wheezing) were examined (1) at the unadjusted level, (2) after adjusting for smoking heaviness and duration, and (3) after also adjusting for environmental exposure and demographics.

RESULTS: In fully-adjusted weighted regressions, those reporting TTFC ≤ 5 minutes were three times as likely to have COPD (confidence interval [CI] = 1.30-8.77), had a 3% lower forced vital capacity expired in the first second (FEV1/FVC) (CI = -0.051 to -0.009), were seven times as likely to report coughing (CI = 1.96-26.41), and 16 times as likely to report bringing up phlegm (CI = 3.43-74.82), relative to those reporting TTFC > 60 minutes. Similar associations were often found when comparing TTFC between 5 to 30 minutes and TTFC between 30 to 60 minutes with TTFC > 60 minutes.

CONCLUSIONS: "Addicted" smoking, as measured by earlier TTFC, is associated with a markedly increased risk of spirometry-measured obstructive pulmonary impairment, and of reporting symptoms of coughing and phlegm, even after controlling for smoking behavior and other risk factors for COPD. TTFC may prove valuable in more precisely assessing smokers' risk of pulmonary impairment.

IMPLICATIONS: This study shows that smoking sooner after waking, a reliable indicator of ND, substantially increases the risk of spirometry-defined pulmonary impairment and self-reported symptoms, independently of lifetime and current smoking behavior. This study adds to a small body of literature examining health outcomes associated with higher ND, including outcomes of COPD. The current study overcomes important shortcomings of these existing studies in at least two ways: controlling for other known risk factors for COPD, and using empirical, spirometry-defined outcomes pulmonary function rather than self-reported COPD outcomes.