A smoker with a 7-year history and an average of 12 cigarettes per day has how many pack-years?

A smoker with a 7-year history and an average of 12 cigarettes per day has how many pack-years?

• A. 4.2 pack years
• B. 5.6 pack years
• C. 7.0 pack years
• D. 8.4 pack years

Answer: (A)

Pack-years measure cumulative tobacco exposure by multiplying packs smoked per day by years of smoking. One pack equals 20 cigarettes. For 12 cigarettes daily, that's 12/20 = 0.6 packs per day. Over 7 years, 0.6 × 7 = 4.2 pack-years. So 4.2 is the correct amount. The other values would require different daily consumption: 5.6 would come from about 0.8 packs per day (roughly 16 cigarettes daily) for 7 years; 7.0 from 1 pack per day for 7 years; 8.4 from about 1.2 packs per day (roughly 24 cigarettes daily) for 7 years.

Pack-years measure cumulative tobacco exposure by multiplying packs smoked per day by years of smoking. One pack equals 20 cigarettes. For 12 cigarettes daily, that's 12/20 = 0.6 packs per day. Over 7 years, 0.6 × 7 = 4.2 pack-years. So 4.2 is the correct amount. The other values would require different daily consumption: 5.6 would come from about 0.8 packs per day (roughly 16 cigarettes daily) for 7 years; 7.0 from 1 pack per day for 7 years; 8.4 from about 1.2 packs per day (roughly 24 cigarettes daily) for 7 years.