ABSTRACT
Tobacco use in different forms is known to be a major killer in many countries and is gradually taking center stage in the rest of the world. Pack-years is a way of measuring the extent of a person’s cigarette smoking. This is measured as
pack-years = m1y1 + m2y2 + … +mTyT,
where mt packs of cigarettes are smoked for yt years (t = 1, 2, …, T). If 2 packs a day are smoked for 4 years and 3 packs for 10 years, the pack-years are 2 × 4 + 3 × 10 = 38. As per this definition, one pack-year is smoking one pack a day for 1 year that actually means 365 packs a year.
