Smoking intensity (pack/day) is a better measure than pack-years or smoking status for modeling cardiovascular disease outcomes

Abstract

Objectives: Smoking as an epidemiological exposure can be quantified in many ways including duration, intensity, pack-years, recency, and age at initiation. However, it is not clear which of these are most important for cardiovascular disease (CVD) and how they should be modeled.

Study design and setting: Using the Multi-Ethnic Study of Atherosclerosis, Cox models for time to incident CVD adjusted for age, sex, race/ethnicity, education category, and income category were compared which included various characterizations of smoking history.

Results: Duration, age at starting, time since quitting, and noncigarette forms of smoking were not independently associated with CVD, whereas baseline current intensity was associated with CVD [e.g., hard CVD hazard ratio 1 pack/d of 1.85 95% confidence interval (1.33, 2.57)]. Former smokers, regardless of duration, intensity, or recency, were not at increased risk, suggesting that risk may risk may drop precipitously from the time of quitting. For CVD events, representing smoking exposure as baseline smoking intensity produced better model fit as measured by Akaike information criterion than models using smoking status or pack-years.

Conclusion: The association of smoking with incident CVD events was well captured by including a simple term for baseline smoking intensity.

Keywords: Cardiovascular disease; Cohort; Intensity; Multi-Ethnic Study of Atherosclerosis; Pack-years; Smoking.