| Lifetime smoking exposure is quantified in "pack years", where one "pack year" is 20 cigarettes smoked/day for one year.1 Quantification of pack years smoked is important in clinical care where degree of tobacco exposure is closely correlated to risk of disease. Smokers suffer an irreversible forced expiratory volume in one second (FEV1) loss of 4.4–10.4 ml per pack year smoked.2,3 There is a strong dose–response relation between the number of pack years smoked and the risk,4 severity,5 and mortality6 of chronic obstructive pulmonary disease and the risk of lung cancer.7 Pack year smoking histories are important for quantification of tobacco exposure in research for direct study, to define patient groups or to determine confounding effects of smoking on outcomes from other exposures. Although the number of ready made Tax Free Cigarettes can easily be quantified in pack years, there is no well established method for measuring loose tobacco use. In this study we determined whether there was a need to quantify loose tobacco exposure and developed a simple method for converting loose tobacco use into pack years. |
