Exponential cigarette-pack-year index (ECPYI).

OBJECTIVES

Traditional tobacco exposure metrics like the cigarette-pack-year (CPY) fail to capture the stronger, non-linear influence of smoking duration relative to intensity on lung cancer risk. To address this, the Exponential Cigarette-Pack-Year Index (ECPYI) was proposed, a novel metric that incorporates the square of cigarette consumption and the fourth power of smoking duration to better reflect their differential effects on risk.

STUDY

DESIGN

Methodological formulation and simulation-based comparative analysis.

METHODS

ECPYI is calculated using the formula: ECPYI = ln (cigarettes2 × years4), offering a biologically informed alternative to CPY. Comparative analyses illustrate how ECPYI distinguishes between patterns of exposure that CPY treats equivalently.

RESULTS

Despite identical CPY values, ECPYI varied substantially across scenarios, reflecting the disproportionate risk posed by longer smoking duration. Graphical comparisons showed ECPYI increasing non-linearly with time, unlike CPY, which remained constant.

CONCLUSIONS

ECPYI provides a more accurate and practical tool for assessing smoking-related lung cancer risk, aligning with epidemiological evidence. While simple to compute and useful in public health contexts, it currently omits key individual risk modifiers such as age at initiation and inhalation patterns.