Pack-year

2023-07-14T10:00:57Z

103.41.95.8: /* Definition */

{{Short description|Clinical quantification of cigarette smoking}}
{{refimprove|date=November 2018}}
A '''pack-year''' is a clinical [[Quantification (science)|quantification]] of [[cigarette smoking]] used to measure a person's exposure to [[Tobacco products|tobacco]]. This is used to assess their risk of developing [[lung cancer]] or other pathologies related to tobacco use. However, it is difficult to rely on the assessment based on the pack-year due to the different nature of the packaging by different companies.

==Definition==
The pack-year is a unit for measuring the amount a person has smoked over a long period of time. It is calculated by multiplying the number of packs of [[cigarette]]s smoked per day by the number of years the person has smoked. For example, 1 pack-year is equal to smoking 20 cigarettes (1 pack) per day for 1 year, or 40 cigarettes per day for half a year, and so on.<ref>http://www.cancer.gov/dictionary?CdrID=306510 National Cancer Institute definition of pack year</ref>

One pack-year is the equivalent of 365 packs of cigarettes or 7,300 cigarettes, in a year as smoker.

==Calculation==

Number of pack-years = (packs smoked per day) × (years as a smoker)

''or''

Number of pack-years = (number of ''cigarettes'' smoked per day/20) × number of years smoked.
(1 pack has 20 cigarettes in some countries)

Note that despite the unit being called a "pack-year," the actual unit is simply a number of packs (as noted above).
: <math>
\begin{align}
1 \text{ pack-year} &= \frac{1 \text{ pack}}{\text{day}} \cdot 1 \text{ year}\\
&= \frac{1 \text{ pack}}{\text{day}} \cdot 365 \text{ days}\\
&= 365 \text{ packs}\\
&= 365 \text{ packs}\cdot\frac{20 \text{ cigarettes}}{\text{pack}}\\
&= 7,300 \text{ cigarettes}
\end{align}
</math>

For example: a person who has smoked 15 cigarettes a day for 40 years has a (15/20) x 40 = 30 pack-year smoking history.

''One'' pack-year is smoking 20 cigarettes a day for one year. If someone has smoked 10 cigarettes a day for 6 years they would have a 3 pack-year history. Someone who has smoked 40 cigarettes (2 packs) daily for 20 years has a 40 pack-year history.

==Significance and usage==
Quantification of pack-years smoked is important in clinical care, where degree of [[tobacco]] exposure is correlated to risk of disease such as lung cancer<ref name="isbn92-4-159628-7">{{Citation | author = World Health Organization | title = WHO Report on the Global Tobacco Epidemic 2008: The MPOWER Package | publisher = World Health Organization | location = Geneva | year = 2008 | isbn = 978-92-4-159628-2 | url =https://www.who.int/tobacco/mpower/mpower_report_full_2008.pdf | archive-url =https://web.archive.org/web/20080308173338/http://www.who.int/tobacco/mpower/mpower_report_full_2008.pdf | url-status =dead | archive-date =March 8, 2008 |access-date=September 6, 2017}}</ref> and heart disease.<ref name="smoking-and-cardiovascular-disease">{{Citation | author = Johns Hopkins Medicine | title = Smoking and Cardiovascular Disease | publisher = Johns Hopkins Medicine | year = 2021 | url =https://www.hopkinsmedicine.org/health/conditions-and-diseases/smoking-and-cardiovascular-disease |access-date=June 1, 2021}}</ref>

==References==
{{reflist}}

[[Category:Smoking]]
[[Category:Medical tests]]

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Pack-year