Measures of impact among the exposed - Revision history

Bosmana fem at 21:06, 22 March 2023

2023-03-22T21:06:48Z

← Older revision		Revision as of 21:06, 22 March 2023
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	* Lisa Lazareck		* Lisa Lazareck
	* Meirion Evans		* Meirion Evans


			[[Category:Measures of Disease Impact]]

Bosmana fem at 08:58, 19 December 2022

2022-12-19T08:58:52Z

← Older revision		Revision as of 08:58, 19 December 2022
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	First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):		First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):

	[[File:2318.~~are~~.gif-550x0.png\|400px\|frameless\|left]]		[[File:2318.ARe.gif-550x0.png\|400px\|frameless\|left]]


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	We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):		We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):

	[[File:1070.~~afe~~-1.gif-550x0.png\|400px\|frameless\|left]]		[[File:1070.AFe-1.gif-550x0.png\|400px\|frameless\|left]]

	Ie = incidence among exposed		Ie = incidence among exposed
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	===Speeding===		===Speeding===
	[[File:0207.~~afe~~-3.gif-550x0.png\|400px\|frameless\|left]]		[[File:0207.AFe-3.gif-550x0.png\|400px\|frameless\|left]]

	This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.		This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.

	===Drunk driving===		===Drunk driving===
	[[File:7343.~~afe~~-4.gif-550x0.png\|400px\|frameless\|left]]		[[File:7343.AFe-4.gif-550x0.png\|400px\|frameless\|left]]

	This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.		This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.
Line 73:		Line 73:

	We would then have the following:		We would then have the following:
	[[File:2055.~~pfe~~-1.gif-550x0.png\|400px\|frameless\|left]]		[[File:2055.PFe-1.gif-550x0.png\|400px\|frameless\|left]]

	Ie = incidence among exposed		Ie = incidence among exposed
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	To calculate the preventable fraction:		To calculate the preventable fraction:
	[[File:4861.~~pfe~~-1.gif-550x0.png\|400px\|frameless\|left]]		[[File:4861.PFe-1.gif-550x0.png\|400px\|frameless\|left]]

	[[File:1882.~~pfe~~-2b.GIF-550x0.png\|400px\|frameless\|left]]		[[File:1882.PFe-2b.GIF-550x0.png\|400px\|frameless\|left]]


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	==Attributable fraction in case-control studies==		==Attributable fraction in case-control studies==
	[[File:4061.~~afe~~-5.gif-550x0.png\|400px\|frameless\|left]]		[[File:4061.AFe-5.gif-550x0.png\|400px\|frameless\|left]]

	[[File:6428.~~pfe~~-3.gif-550x0.png\|400px\|frameless\|left]]		[[File:6428.PFe-3.gif-550x0.png\|400px\|frameless\|left]]

	AFe = attributable fraction among the exposed		AFe = attributable fraction among the exposed

Bosmana fem at 08:57, 19 December 2022

2022-12-19T08:57:53Z

← Older revision		Revision as of 08:57, 19 December 2022
Line 11:		Line 11:
	First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):		First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):

	[[File:2318.~~ARe~~.gif-550x0.png\|400px\|frameless\|left]]		[[File:2318.are.gif-550x0.png\|400px\|frameless\|left]]


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	We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):		We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):

	[[File:1070.~~AFe~~-1.gif-550x0.png\|400px\|frameless\|left]]		[[File:1070.afe-1.gif-550x0.png\|400px\|frameless\|left]]

	Ie = incidence among exposed		Ie = incidence among exposed
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	===Speeding===		===Speeding===
	[[File:0207.~~AFe~~-3.gif-550x0.png\|400px\|frameless\|left]]		[[File:0207.afe-3.gif-550x0.png\|400px\|frameless\|left]]

	This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.		This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.

	===Drunk driving===		===Drunk driving===
	[[File:7343.~~AFe~~-4.gif-550x0.png\|400px\|frameless\|left]]		[[File:7343.afe-4.gif-550x0.png\|400px\|frameless\|left]]

	This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.		This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.
Line 73:		Line 73:

	We would then have the following:		We would then have the following:
	[[File:2055.~~PFe~~-1.gif-550x0.png\|400px\|frameless\|left]]		[[File:2055.pfe-1.gif-550x0.png\|400px\|frameless\|left]]

	Ie = incidence among exposed		Ie = incidence among exposed
Line 98:		Line 98:

	To calculate the preventable fraction:		To calculate the preventable fraction:
	[[File:4861.~~PFe~~-1.gif-550x0.png\|400px\|frameless\|left]]		[[File:4861.pfe-1.gif-550x0.png\|400px\|frameless\|left]]

	[[File:1882.~~PFe~~-2b.GIF-550x0.png\|400px\|frameless\|left]]		[[File:1882.pfe-2b.GIF-550x0.png\|400px\|frameless\|left]]


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	==Attributable fraction in case-control studies==		==Attributable fraction in case-control studies==
	[[File:4061.~~AFe~~-5.gif-550x0.png\|400px\|frameless\|left]]		[[File:4061.afe-5.gif-550x0.png\|400px\|frameless\|left]]

	[[File:6428.~~PFe~~-3.gif-550x0.png\|400px\|frameless\|left]]		[[File:6428.pfe-3.gif-550x0.png\|400px\|frameless\|left]]

	AFe = attributable fraction among the exposed		AFe = attributable fraction among the exposed

Bosmana fem at 08:52, 19 December 2022

2022-12-19T08:52:06Z

← Older revision		Revision as of 08:52, 19 December 2022
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	==Attributable risk among the exposed (ARe)==		==Attributable risk among the exposed (ARe)==
	The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals that can be attributed to the exposure. It provides information about the absolute effects of exposure ~~[1]~~.		The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals that can be attributed to the exposure. It provides information about the absolute effects of exposure<ref>Greenland S, Robins JM. Conceptual problems in the definition and interpretation of attributable fractions. Am J Epidemiol 1988;128:1185-97.</ref>.

	===EXAMPLE: Reducing automobile related deaths===		===EXAMPLE: Reducing automobile related deaths===
Line 11:		Line 11:
	First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):		First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):

	[[2318.ARe.gif-550x0.png]]		[[File:2318.ARe.gif-550x0.png\|400px\|frameless\|left]]


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	We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):		We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):

	[[1070.AFe-1.gif-550x0.png]]		[[File:1070.AFe-1.gif-550x0.png\|400px\|frameless\|left]]

	Ie = incidence among exposed		Ie = incidence among exposed
Line 50:		Line 50:
	==Attributable fraction in cohort studies==		==Attributable fraction in cohort studies==
	In a cohort study, the attributable fraction among the exposed (AFe) is:		In a cohort study, the attributable fraction among the exposed (AFe) is:
			[[File:1488.AFe-2.gif-550x0.png\|400px\|frameless\|left]]
	[[1488.AFe-2.gif-550x0.png]]

	Ie = incidence among exposed		Ie = incidence among exposed
Line 62:		Line 61:

	===Speeding===		===Speeding===
			[[File:0207.AFe-3.gif-550x0.png\|400px\|frameless\|left]]
	[[0207.AFe-3.gif-550x0.png]]

	This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.		This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.

	===Drunk driving===		===Drunk driving===
	[[7343.AFe-4.gif-550x0.png]]		[[File:7343.AFe-4.gif-550x0.png\|400px\|frameless\|left]]

	This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.		This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.
Line 75:		Line 73:

	We would then have the following:		We would then have the following:
			[[File:2055.PFe-1.gif-550x0.png\|400px\|frameless\|left]]
	[[2055.PFe-1.gif-550x0.png]]

	Ie = incidence among exposed		Ie = incidence among exposed
Line 83:		Line 80:

	RR = risk ratio		RR = risk ratio



	Table. Vaccine effectiveness in the population of Anystate, 2010		Table. Vaccine effectiveness in the population of Anystate, 2010
Line 103:		Line 98:

	To calculate the preventable fraction:		To calculate the preventable fraction:
	[[4861.PFe-1.gif-550x0.png]]		[[File:4861.PFe-1.gif-550x0.png\|400px\|frameless\|left]]

	~~[[1882.PFe-2b.GIF-550x0.png~~]]

			[[File:1882.PFe-2b.GIF-550x0.png\|400px\|frameless\|left]]


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	==Attributable fraction in case-control studies==		==Attributable fraction in case-control studies==
	[[4061.AFe-5.gif-550x0.png]]		[[File:4061.AFe-5.gif-550x0.png\|400px\|frameless\|left]]

	[[6428.PFe-3.gif-550x0.png]]		[[File:6428.PFe-3.gif-550x0.png\|400px\|frameless\|left]]

	AFe = attributable fraction among the exposed		AFe = attributable fraction among the exposed
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	Two assumptions are made in substituting OR for RR:		Two assumptions are made in substituting OR for RR:
			* controls represent the general population
			* the prevalence of exposure is low<ref>Cole P, MacMahon B. Attributable risk percent in case-control studies. Br J Prev Soc Med 1971;25:242-4.</ref>.

	~~that controls are representative of the general population~~		Methods are also available for calculating attributable fractions for matched case-control studies.<ref>Kuritz SJ, Landis JR. Attributable risk ratio estimation from matched-pairs case-control data. Am J Epidemiol 1987;125:324-8.</ref>

	~~that the prevalence of exposure is low [2].~~

	Methods are also available for calculating attributable fractions for matched case-control studies ~~[3]~~.


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	=References =		=References =
	~~1. Greenland S, Robins JM. Conceptual problems in the definition and interpretation of attributable fractions. Am J Epidemiol 1988;128:1185-97.~~		<references/>
	~~2. Cole P, MacMahon B. Attributable risk percent in case-control studies. Br J Prev Soc Med 1971;25:242-4.~~
	~~3. Kuritz SJ, Landis JR. Attributable risk ratio estimation from matched-pairs case-control data. Am J Epidemiol 1987;125:324-8.~~

Bosmana fem at 08:42, 19 December 2022

2022-12-19T08:42:12Z

← Older revision		Revision as of 08:42, 19 December 2022
Line 1:		Line 1:
	==Attributable risk among the exposed (ARe)==		==Attributable risk among the exposed (ARe)==
	The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals that can be attributed to the exposure. It provides information about the absolute effects of ~~the~~ exposure [1].		The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals that can be attributed to the exposure. It provides information about the absolute effects of exposure [1].

	===EXAMPLE: Reducing automobile related deaths===		===EXAMPLE: Reducing automobile related deaths===
	Let us suppose that we are in charge of a prevention ~~programme~~ and that our goal is to reduce automobile-related deaths. However, we have a limited budget and we want to have the maximum impact on reducing deaths.		Let us suppose that we are in charge of a prevention program and that our goal is to reduce automobile-related deaths. However, we have a limited budget and want to have the maximum impact on reducing deaths.

	We decide to conduct a cohort study of 10,000 drivers to examine risk factors for automobile-related deaths. We are particularly interested in factors like drunk driving and speeding since we believe interventions are feasible.		We decide to conduct a cohort study of 10,000 drivers to examine risk factors for automobile-related deaths. We are particularly interested in factors like drunk driving and speeding since we believe interventions are feasible.

	We would like to quantify the disease burden (deaths) ~~due to the~~ exposure in ~~each of the two~~ groups (drunk drivers and speeding drivers). This means that in each exposed group we are aiming to measure how many ~~of the~~ deaths ~~that~~ occur ~~are~~ due to drunk driving and to speeding respectively.		We would like to quantify the disease burden (deaths) from exposure in both groups (drunk drivers and speeding drivers). This means that in each exposed group, we are aiming to measure how many deaths occur due to drunk driving and speeding, respectively.

	First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):		First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):
Line 59:		Line 59:
	RR = risk ratio		RR = risk ratio

	In the example of speeding and drunk driving we therefore have:		In the example of speeding and drunk driving, we therefore have:

	===Speeding===		===Speeding===
Line 65:		Line 65:
	[[0207.AFe-3.gif-550x0.png]]		[[0207.AFe-3.gif-550x0.png]]

	This means that (if speeding causes driving related deaths) 80% of driving related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.		This means that (if speeding causes driving-related deaths) 80% of driving-related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.

	===Drunk driving===		===Drunk driving===
	[[7343.AFe-4.gif-550x0.png]]		[[7343.AFe-4.gif-550x0.png]]

	This means that (if drunk driving causes driving related deaths) 91% of driving related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.		This means that (if drunk driving causes driving-related deaths) 91% of driving-related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.

	These examples illustrate what happens if exposure increases risk of disease. If exposure prevents disease (e.g. vaccination), the attributable risk is often called the preventable fraction among the exposed (PFe).		These examples illustrate what happens if exposure increases the risk of disease. If exposure prevents disease (e.g. vaccination), the attributable risk is often called the preventable fraction among the exposed (PFe).

	We would then have the following:		We would then have the following:
Line 113:		Line 113:
	306,045 x (1.72/1,000) = 526 cases		306,045 x (1.72/1,000) = 526 cases

	We have calculated that the vaccine ~~was able to prevent~~ 72% of these cases (the preventable fraction).		We have calculated that the vaccine prevented 72% of these cases (the preventable fraction).

	The estimated number of cases that were prevented by the vaccination ~~programme~~ is therefore:		The estimated number of cases that were prevented by the vaccination program is therefore:

	526 x 0.72 = 379 cases		526 x 0.72 = 379 cases

Bosmana fem at 08:31, 19 December 2022

2022-12-19T08:31:47Z

← Older revision		Revision as of 08:31, 19 December 2022
Line 171:		Line 171:
	2. Cole P, MacMahon B. Attributable risk percent in case-control studies. Br J Prev Soc Med 1971;25:242-4.		2. Cole P, MacMahon B. Attributable risk percent in case-control studies. Br J Prev Soc Med 1971;25:242-4.
	3. Kuritz SJ, Landis JR. Attributable risk ratio estimation from matched-pairs case-control data. Am J Epidemiol 1987;125:324-8.		3. Kuritz SJ, Landis JR. Attributable risk ratio estimation from matched-pairs case-control data. Am J Epidemiol 1987;125:324-8.


			=credits=
			===FEM Editor 2007===
			* Meirion Evans
			===Original Authors===
			* Alain Moren
			* Marta Valenciano
			* Thomas Grein
			===FEM Contributors===
			* Lisa Lazareck
			* Meirion Evans

Bosmana fem: Created page with "==Attributable risk among the exposed (ARe)== The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals tha..."

2022-12-19T08:11:27Z

Created page with "==Attributable risk among the exposed (ARe)== The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals tha..."

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==Attributable risk among the exposed (ARe)==
The attributable risk among the exposed (risk difference or excess risk) is the proportion of cases among exposed individuals that can be attributed to the exposure. It provides information about the absolute effects of the exposure [1].

===EXAMPLE: Reducing automobile related deaths===
Let us suppose that we are in charge of a prevention programme and that our goal is to reduce automobile-related deaths. However, we have a limited budget and we want to have the maximum impact on reducing deaths.

We decide to conduct a cohort study of 10,000 drivers to examine risk factors for automobile-related deaths. We are particularly interested in factors like drunk driving and speeding since we believe interventions are feasible.

We would like to quantify the disease burden (deaths) due to the exposure in each of the two groups (drunk drivers and speeding drivers). This means that in each exposed group we are aiming to measure how many of the deaths that occur are due to drunk driving and to speeding respectively.

First, we calculate the risk difference between the exposed and unexposed. This is known as the attributable risk among the exposed (ARe):

[[2318.ARe.gif-550x0.png]]

The study gives the following results:

Table. Risk of death from speeding or drunk driving, Anystate, 2010
Speeding
{| class="wikitable"
! Speeding !! Total drivers !! No. of deaths !! Risk of death !! Attributable risk (exposed)
|-
| Yes || 2,000 || 100 || 50 || 50 - 10 = 40/1,000
|-
| No || 8,000 || 80 || 10 ||
|-
| || || || ||
|-
| Drunk driving || Total drivers || No. of deaths || Risk of death per 1,000 || Attributable risk (exposed)
|-
| Yes || 300 || 45 || 150 || 150 - 14 = 136/1,000
|-
| No || 9,700 || 135 || 14
|}

We can also express attributable risk as the percentage of all deaths among the exposed that can be attributed to the exposure. .This is known as the attributable fraction among the exposed (AFe):

[[1070.AFe-1.gif-550x0.png]]

Ie = incidence among exposed

Iu = incidence among unexposed

If the risk factor is causal, then the attributable fraction among the exposed corresponds to the proportion of disease among the exposed that can:

* be attributed to the exposure
* be avoided by eliminating the exposure.

==Attributable fraction in cohort studies==
In a cohort study, the attributable fraction among the exposed (AFe) is:

[[1488.AFe-2.gif-550x0.png]]

Ie = incidence among exposed

Iu = incidence among unexposed

RR = risk ratio

In the example of speeding and drunk driving we therefore have:

===Speeding===

[[0207.AFe-3.gif-550x0.png]]

This means that (if speeding causes driving related deaths) 80% of driving related deaths among speeding drivers can be attributed to speeding. They could be avoided if speeding did not occur.

===Drunk driving===
[[7343.AFe-4.gif-550x0.png]]

This means that (if drunk driving causes driving related deaths) 91% of driving related deaths among drunk drivers can be attributed to drunk driving. They could be avoided if drunk driving did not occur.

These examples illustrate what happens if exposure increases risk of disease. If exposure prevents disease (e.g. vaccination), the attributable risk is often called the preventable fraction among the exposed (PFe).

We would then have the following:

[[2055.PFe-1.gif-550x0.png]]

Ie = incidence among exposed

Iu = incidence among unexposed

RR = risk ratio

Table. Vaccine effectiveness in the population of Anystate, 2010
{| class="wikitable"
! No. of cases !! Cases per 1,000 !! Risk ratio (RR) !!
|-
| Population || || || ||
|-
| Vaccinated || 306,045 || 150 || 0.49 || 0.28
|-
| Unvaccinated || 298,655 || 515 || 1.72 || Reference
|-
| || || || ||
|-
| Total || 604,700 || 665 || 1.1
|}

To calculate the preventable fraction:
[[4861.PFe-1.gif-550x0.png]]

[[1882.PFe-2b.GIF-550x0.png]]

The expected number of cases among the vaccinated population, if they were unvaccinated, is:

306,045 x (1.72/1,000) = 526 cases

We have calculated that the vaccine was able to prevent 72% of these cases (the preventable fraction).

The estimated number of cases that were prevented by the vaccination programme is therefore:

526 x 0.72 = 379 cases

==Attributable fraction in case-control studies==
[[4061.AFe-5.gif-550x0.png]]

[[6428.PFe-3.gif-550x0.png]]

AFe = attributable fraction among the exposed

PFe = preventable fraction among the exposed

OR = odds ratio

Two assumptions are made in substituting OR for RR:

that controls are representative of the general population

that the prevalence of exposure is low [2].

Methods are also available for calculating attributable fractions for matched case-control studies [3].

==Synopsis==
===Attributable risk among the exposed (ARe)===
* The number of cases (amount of disease) among the exposed that can be attributed to the exposure
* What is the risk among the exposed that is due to the exposure?
* This is calculated as the absolute difference between risk in the exposed and risk in the unexposed
* It assumes that the causal effect is entirely due to the risk factor

Synonyms:
* Attributable risk (exposed)
* Attributable benefit (exposed)
* Risk difference / Excess risk
* Rate difference / Excess rate
* Absolute risk reduction

===Attributable fraction among the exposed (AFe)===
* The proportion of cases (percentage of disease) among the exposed that can be attributed to the exposure
* Attributable risk expressed as a proportion of the risk in the exposed
* What is the proportion of disease among the exposed that:
** can be attributed to the exposure?
** can be prevented if the exposure is eliminated?

Synonyms:
* Attributable fraction (exposed)
* Attributable proportion / Attributable risk percent (exposed)
* Aetiological fraction / Preventable fraction (exposed)
* Relative risk reduction

=References =
1. Greenland S, Robins JM. Conceptual problems in the definition and interpretation of attributable fractions. Am J Epidemiol 1988;128:1185-97.
2. Cole P, MacMahon B. Attributable risk percent in case-control studies. Br J Prev Soc Med 1971;25:242-4.
3. Kuritz SJ, Landis JR. Attributable risk ratio estimation from matched-pairs case-control data. Am J Epidemiol 1987;125:324-8.