Assessment of an optimised tobacco smoking exposure calculation

<bold>Background:</bold> Tobacco smoke is a determinant of lung function in exposed individuals. The “pack-year history”(PYHx) is commonly used to quantify tobacco exposure [(years smoked*avg_daily_cigarettes)/20] but may be insensitive to periodic variations in intensity of smoking. We explored whether a refined approach to PHYx calculation results in estimates which vary significantly from the traditional approach, and correlates more closely with lung function. <bold>Methods:</bold> We surveyed consecutive ever-smoking patients attending the St Vincent’s University Hospital pulmonary function laboratory over a 3-week period. Traditional PYHx (PYHxtrad) were calculated and detailed PHYx (PYHxdetailed) were calculated using average daily tobacco consumption for each smoking decade. Correlation between exposure and FEV1%predicted was assessed. <bold>Results:</bold> 105 patients were included. PYHxtrad and PYHxdetailed were strongly correlated (rho 0.9), however increasing PYHxtrad was associated with a decrease in the corresponding PYHxdetailed (−0.76% PYHxdetailed per increase in PYHxtrad, p=0.001, figure 1). PYHxdetailed correlated more strongly with FEV1%predicted (−0.43% per PYHxdetailed, p<0.001, R2 0.118) vs -0.19% per PYHxtrad, p=0.043, R2 0.043, respectively). <bold>Conclusions:</bold> PYHxtrad calculation may overestimate tobacco smoke exposure, especially at higher calculations. A refined approach correlates more closely with FEV1%predicted and may offer a more accurate estimate of exposure, with potential to improve effect size estimation in the research setting when adjusting analysis for smoke exposure. Further validation is planned.