Journal Article

Modeling Smoking History: A Comparison of Different Approaches

Karen Leffondré, Michal Abrahamowicz, Jack Siemiatycki and Bernard Rachet

in American Journal of Epidemiology

Published on behalf of Johns Hopkins Bloomberg School of Public Health

Volume 156, issue 9, pages 813-823
Published in print November 2002 | ISSN: 0002-9262
Published online November 2002 | e-ISSN: 1476-6256 | DOI:
Modeling Smoking History: A Comparison of Different Approaches

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The impact of cigarette smoking on various diseases is studied frequently in epidemiology. However, there is no consensus on how to model different aspects of smoking history. The aim of this investigation was to elucidate the impact of several decisions that must be made when modeling smoking variables. The authors used data on lung cancer from a case-control study undertaken in Montreal, Quebec, Canada, in 1979–1985. The roles of smoking status, intensity, duration, cigarette-years, age at initiation, and time since cessation were investigated using time-dependent variables in an adaptation of Cox’s model to case-control data. The authors reached four conclusions. 1) The estimated hazard ratios for current and ex-smokers depend strongly on how long subjects are required to not have smoked to be considered “ex-smokers.” 2) When the aim is to estimate the effect of continuous smoking variables, a simple approach can be used (and is proposed) to separate the qualitative difference between never and ever smokers from the quantitative effect of smoking. 3) Using intensity and duration as separate variables may lead to a better model fit than using their product (cigarette-years). 4) When estimating the effects of time since cessation or age at initiation, it is still useful to use cigarette-years, because it reduces multicollinearity.

Keywords: case-control studies; epidemiologic methods; multicollinearity; multivariate analysis; neoplasms; proportional hazard; smoking; time-dependent covariate; Abbreviation: AIC, Akaike’s Information Criterion.

Journal Article.  7271 words.  Illustrated.

Subjects: Public Health and Epidemiology

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