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Smoking duration alone provides stronger risk estimates of chronic obstructive pulmonary disease than pack-years

Surya P Bhatt, Young-il Kim, Kathy F Harrington, et al.
Thorax 2018;73:414–21

Tobacco smoking is known to be one of the greatest risk factors for chronic obstructive pulmonary disease (COPD). When comparing the strength of association between COPD and smoking, the parameters used to define tobacco exposure often explore the amount smoked over a long period of time (i.e. pack-years). However, other factors, such as the duration of tobacco smoking, may provide a more representative depiction of tobacco exposure than those currently used. In this study, Dr Surya Bhatt and colleagues aimed to examine the relative contributions of pack-years, cigarettes smoked per day (cigarettes/day) and duration on the development of COPD, particularly its effect on airflow obstruction.

They conducted a cross-sectional study analysing data from a large multicentre cohort, COPDGene, including 10,187 subjects. Findings showed that the parameter most associated with estimates of COPD (e.g. forced expiratory volume in 1 second (FEV1)) was smoking duration. In particular, smoking duration produced the greatest adjusted effect size in airflow obstruction, CT emphysema and respiratory morbidity than cigarettes/day and pack-years. Researchers concluded that smoking duration may provide the strongest risk estimate of COPD than other defining parameters of tobacco exposure. This may suggest that smoking duration should be optimised as a defining factor of tobacco exposure in epidemiological studies to accurately represent the association between smoking and COPD.

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