Is 20 pack years a lot?

What does 20 pack years represent?

One pack year is 20 cigarettes a day for one year, or 7,300 cigarettes. Twenty pack years is 20 times that: 146,000 cigarettes. Many different histories add up to the same figure:

The last two rows use the calculator’s conversions: a cigar counts as 4 cigarettes, and 1 g of loose tobacco as 2 cigarettes, so 70 g a week is 20 cigarettes a day. See how the calculation works.

Does it matter how the pack years built up?

The site’s FAQs say it does. FAQ 2 compares 5 cigarettes a day for 20 years with 20 a day for 5 years: both are 5 pack years, “but the risk of smoking related ill health is very much greater in the former smoker”. It calls pack years “only a crude imprecise description of smoking related exposure”.

The first three rows of the table are the same kind of comparison: 20 pack years smoked over 40, 20 or 10 years. On FAQ 2’s reasoning, 10 a day for 40 years carries more risk than 40 a day for 10 years, although both come to 20 pack years.

In 2023 Dr Masters wrote that “Years smoked and active smoking are the most useful terms to ascertain risk.” The calculator’s optional history step records both: see pack years and years smoked.

Where does 20 pack years appear in published criteria?

In the United States, the US Preventive Services Task Force (USPSTF) recommended in March 2021 “annual screening for lung cancer with LDCT in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years.” LDCT is a low-dose CT scan. This replaced its 2013 criteria of age 55 to 80 and 30 pack years: see lung cancer screening in the US.

Screening stops once a person has not smoked for 15 years.

Does England use 20 pack years?

No. England’s Lung Cancer Screening Programme offers a lung health check to people aged 55 to 74 who have ever smoked and are registered with a GP practice in England. Whether someone is then offered a scan depends on a risk score from two risk models, not on a number of pack years: see lung cancer screening in England.

So is 20 pack years a lot?

This site cannot say what a pack year figure means for one person’s health: the calculator gives general information, not personal clinical advice. Pack years do not tell you whether you have a lung condition. If you are worried about your health, speak to your GP practice or use NHS 111.