Pack Year - Smoking
Pack Year = Number of pack of cigarettes smoked per day x Number of years of the person has smoked 1 pack = 20 cigarettes 1 pack year = 1 pack per day for 1 year (20 cigarettes per day for 1 year) = 2 packs per day for 0.5 year (40 cigarette per day for 6 months) 1 pack year = 365.24 packs of cigarettes = 7305 cigarettes Example A male patient smoked 15 cigarettes per day for 40 years = 15/20 x 40 = 30 pack years Risk for development of bronchogenic carcinoma increases when pack years exceed 40 Example 20 cigarette per day for 40 years 40 cigarette per day for 20 years 80 cigarette per day for 10 years