Abstract 5246: Lifetime trajectories of cigarette smoking and cancer mortality among older adults in a large cohort in the United States
Authors: Inoue-Choi Maki , Kelly Scott P. , Choi Kelvin , Freedman Neal D. 
Published: August 2018

Abstract
Background: Despite declining prevalence, cigarette smoking causes about 30% of all cancer deaths in the United States. More than a quarter of daily cigarette smokers in the United States smoke 10 or less cigarettes per day (CPD), encompassing a heterogeneous group of lifelong low-intensity smokers and formerly heavier smokers who have cut down their CPD. The impact of prior smoking history on the disease risks of low-intensity cigarette smokers is poorly understood.
Methods: In the National Institutes of Health-AARP Diet and Health Study, a prospective cohort study of older adults in the United States, a questionnaire administered in 2004-2005 assessed CPD during nine age-periods over the lifetime (&lt;15 to ≥70). This analysis included 121,025 men and women aged 60-82 who reported never smoking cigarettes (n=110,444) or currently smoking &lt;1 or 1-10 CPD (low intensity smokers, n=10,581). We used fixed-effects latent class trajectory modeling to define lifetime trajectories of prior CPD smoking history among low-intensity cigarette smokers. Then, we calculated sex-specific multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) for each trajectory relative to never smokers using Cox proportional hazards regression for overall and lung cancer mortality.
Results: We identified nine trajectory patterns in both men and women. Mortality risks varied substantially by trajectory: the HRs for overall cancer mortality ranged from 1.17 to 4.03 in men and 0.83 to 3.42 in women. Similarly, the HRs for lung cancer mortality ranged from 5.20 to 23.88 in men and 8.00 to 23.08 in women. Mortality risks were substantially higher among participants who had cut down their CPD than among participants who reported smoking at low-intensity for all age-periods that they smoked. For example, in men, the HR for lung cancer mortality was 23.88 (95% CI=12.10-47.13) among low-intensity smokers who previously smoked 31-40 CPD, whereas it was 9.36 (95% CI=5.92-14.79) among lifelong 1-10 CPD smokers. Similarly, in women, the HR for lung cancer mortality was 19.76 (95% CI=8.71-44.85) among women who previously smoked 21-30 CPD, whereas it was 9.26 (95% CI=2.98-14.34) among lifelong 1-10 CPD smokers.
Conclusions: In a large prospective cohort study of older adults in the United States, risks among low-intensity smokers for overall and lung-cancer mortality varied substantially by prior smoking history. These results suggest that it is important for risk prediction models, such as for lung cancer-screening, to incorporate lifetime smoking history into their algorithms.
Citation Format: Maki Inoue-Choi, Scott P. Kelly, Kelvin Choi, Neal D. Freedman. Lifetime trajectories of cigarette smoking and cancer mortality among older adults in a large cohort in the United States [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5246.