{"entity":{"id":"pack-year","kind":"term","name":"Pack-year","aka":["pack years","pack-years","packyear","cigarette pack-year","smoking pack-year"],"tldr":"The unit used to measure how much someone has smoked over a lifetime: one pack-year is twenty cigarettes a day for one year. Twenty a day for thirty years, or forty a day for fifteen, are both thirty pack-years.","summary":"A pack-year multiplies the number of packs smoked a day by the number of years of smoking, taking a pack as twenty cigarettes. It is the measure every lung cancer screening rule is written in. The National Lung Screening Trial enrolled people with at least 30 pack-years who smoked or had stopped within 15 years; the US Preventive Services Task Force set its 2013 threshold at 30 pack-years and ages 55 to 80, and lowered it in 2021 to 20 pack-years and ages 50 to 80, a change that widened eligibility substantially and was aimed in part at groups whose lung cancer arises at lower cumulative exposure. England's programme does not use a pack-year cut-off at all: it feeds smoking duration and intensity, with age, body mass index, education, family history and lung disease, into a risk model and screens above a predicted-risk threshold. The unit has a known weakness: it treats twenty a day for thirty years and sixty a day for ten as equivalent, when duration raises lung cancer risk more steeply than intensity does.","asOf":"2026-09-25","wikipedia":"https://en.wikipedia.org/wiki/Pack-year","links":[{"label":"US Preventive Services Task Force, JAMA 2021: screening for lung cancer, recommendation statement (annual low-dose CT at 50 to 80 with 20 pack-years, grade B)","url":"https://doi.org/10.1001/jama.2021.1117"},{"label":"National Lung Screening Trial Research Team, N Engl J Med 2011: reduced lung-cancer mortality with low-dose computed tomographic screening (53,454 people)","url":"https://doi.org/10.1056/nejmoa1102873"},{"label":"Cancer Epidemiol 2023: the value of blood-based measures of liver function and urate in lung cancer risk prediction (388,199 UK Biobank participants; the 1.51 percent six-year threshold)","url":"https://doi.org/10.1016/j.canep.2023.102354"},{"label":"CRUK: lung cancer risk factors (attributable fractions for the UK)","url":"https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/lung-cancer/risk-factors"}],"tags":["lung"],"related":[],"cancers":["lung-cancer","nsclc","sclc"],"sections":[],"technologies":["low-dose-ct-screening","nhs-targeted-lung-health-check"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["targeted-lung-health-check","smoking-cessation","never-smoker-lung-cancer"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Epidemiology & prevention"},"route":"/terms/pack-year/","neighbours":{"cancer":[{"id":"lung-cancer","kind":"cancer","name":"Lung cancer (all types)","route":"/cancers/lung-cancer/"},{"id":"nsclc","kind":"cancer","name":"Non-small-cell lung cancer","route":"/cancers/nsclc/"},{"id":"sclc","kind":"cancer","name":"Small-cell lung cancer","route":"/cancers/sclc/"}],"technology":[{"id":"low-dose-ct-screening","kind":"technology","name":"Low-dose CT lung screening","route":"/technologies/low-dose-ct-screening/"},{"id":"nhs-targeted-lung-health-check","kind":"technology","name":"NHS Targeted Lung Health Check (lung cancer screening programme)","route":"/technologies/nhs-targeted-lung-health-check/"}],"term":[{"id":"never-smoker-lung-cancer","kind":"term","name":"Lung cancer in never-smokers","route":"/terms/never-smoker-lung-cancer/"},{"id":"lung-rads","kind":"term","name":"Lung-RADS and nodule reporting","route":"/terms/lung-rads/"},{"id":"pulmonary-nodule","kind":"term","name":"Pulmonary nodule","route":"/terms/pulmonary-nodule/"},{"id":"radon","kind":"term","name":"Radon","route":"/terms/radon/"},{"id":"smoking-cessation","kind":"term","name":"Stopping smoking","route":"/terms/smoking-cessation/"},{"id":"targeted-lung-health-check","kind":"term","name":"Targeted lung health check","route":"/terms/targeted-lung-health-check/"}]}}