Editing Risk factor

{{short description|Variable associated with an increased risk of disease or infection}}
{{about|the concept in epidemiology|other uses|Risk factor (disambiguation)}}
{{expert needed|medicine|reason=defining, "determinant," a complicated, poorly harmonized concept in medicine. Some sources use the term loosely while others use it as a technical term.|date=July 2019}}

In [[epidemiology]], a '''risk factor''' or '''determinant''' is a variable associated with an increased [[risk]] of [[disease]] or [[infection]].<ref name=":0">{{Cite book|title=Disorders of childhood : development and psychopathology|last=Parritz, Robin Hornik|others=Troy, Michael F. (Michael Francis)|isbn=9781337098113|edition= Third|location=Boston, MA|oclc=960031712|date = 2017-05-24}}</ref>{{Rp|38}}

Due to a lack of harmonization across disciplines, '''determinant''', in its more widely accepted [[wikt:determine|scientific meaning]], is often used as a synonym. The main difference lies in the realm of practice: medicine ([[Medicine#Clinical practice|clinical practice]]) versus [[public health]]. As an example from clinical practice, low ingestion of dietary sources of [[vitamin C]] is a known risk factor for developing [[scurvy]]. Specific to public [[health policy]], a determinant is a health risk that is general, abstract, related to inequalities, and difficult for an individual to control.<ref>{{cite book| url=https://www.ncbi.nlm.nih.gov/books/NBK233009/| title=Improving Health in the Community: A Role for Performance Monitoring: 2. Understanding Health and Its Determinants: A Model of the Determinants of Health| chapter=Understanding Health and Its Determinants|publisher=National Academy of Sciences: National Academies Press: Institute of Medicine (US) Committee on Using Performance Monitoring to Improve Community Health| year=1997| isbn=978-0309055345| quote="Unlike a biomedical model that views health as the absence of disease, this dynamic framework includes functional capacity and well-being as health outcomes of interest. It also presents the behavioral and biologic responses of individuals as factors that influence health but are themselves influenced by social, physical, and genetic factors that are beyond the control of the individual."}}</ref><ref>{{cite web| url=https://www.who.int/hia/evidence/doh/en/| title=Health Impact Assessment (HIA): Glossary of terms used| publisher=World Health Organization| access-date=July 20, 2019}}</ref><ref>{{cite web| url=https://www.who.int/hia/about/glos/en/| archive-url=https://web.archive.org/web/20040530022104/http://www.who.int/hia/about/glos/en/| url-status=dead| archive-date=May 30, 2004| title=Health Impact Assessment (HIA): The determinants of health| publisher=World Health Organization| access-date=July 20, 2019}}</ref> For example, poverty is known to be a determinant of an individual's standard of [[health]].

Risk factors may be used to identify high-risk people.

==Correlation vs causation==
Risk factors or determinants are [[correlation]]al and not necessarily [[Causality|causal]], because [[correlation does not prove causation]].  For example, being young cannot be said to cause [[measles]], but young people have a higher rate of measles because they are less likely to have developed [[immunity (medical)|immunity]] during a previous epidemic. [[Statistics|Statistical]] methods are frequently used to assess the strength of an association and to provide causal evidence, for example in the [[British doctors study|study]] of the link between smoking and [[lung cancer]]. Statistical  analysis along with the biological sciences can establish that risk factors are causal.  Some prefer the term risk factor to mean causal determinants of increased rates of disease, and for unproven links to be called possible risks, associations, etc.{{citation needed|date=July 2020}}

When done thoughtfully and based on research, identification of risk factors can be a strategy for [[Screening (medicine)|medical screening]].<ref name="WaldHackshaw1999">{{cite journal|last1=Wald|first1=N. J.|last2=Hackshaw|first2=A. K.|last3=Frost|first3=C. D.|title=When can a risk factor be used as a worthwhile screening test?|journal=BMJ|volume=319|issue=7224|year=1999|pages=1562–1565|issn=0959-8138|doi=10.1136/bmj.319.7224.1562|pmc=1117271|pmid=10591726}}</ref>

==Terms of description==
Mainly taken from [[risk factors for breast cancer]], risk factors can be described in terms of, for example:
* [[Relative risk]], such as "A woman is more than 100 times more likely to develop breast cancer in her 60s than in her 20s."<ref name=Margolese>{{cite book|vauthors=Margolese RG, Fisher B, Hortobagyi GN, Bloomer WD |veditors=Bast RC, Kufe DW, Pollock RE |title=Cancer Medicine |edition=5th |publisher=B. C. Decker |location=Hamilton, Ontario |year=2000 |chapter=Neoplasms of the Breast |at=§Risk Factors |isbn=1-55009-113-1 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK20900/#A29677 |access-date=27 January 2011 |display-editors=etal}}</ref>
* [[Odds ratio]], such as "The odds of developing breast cancer are approximately 2.45 times higher for women with two or more affected first-degree relatives compared to those without a family history."<ref name=BreastCancerRisk>{{cite journal|vauthors=Antoniou AC, Pharoah PD, Narod S, Risch HA, Eyfjord JE, Hopper JL, Loman N, Olsson H, Johannsson O, Borg Å |title=Average risks of breast and ovarian cancer associated with BRCA1 or BRCA2 mutations detected in case series unselected for family history: a combined analysis of 22 studies |journal=American Journal of Human Genetics |volume=72 |issue=5 |pages=1117–1130 |year=2003 |doi=10.1086/375033 |pmid=12677558|pmc=1180265 }}</ref>
* Fraction of [[Incidence_(epidemiology) | incidences]] occurring in the group having the property of or being exposed to the risk factor, such as "99% of breast cancer cases are diagnosed in women."<ref name="Giordano">{{cite journal |vauthors=Giordano SH, Cohen DS, Buzdar AU, Perkins G, Hortobagyi GN |title=Breast carcinoma in men: a population-based study |journal=Cancer |volume=101 |issue=1 |pages=51–7 |date=July 2004 |pmid=15221988 |doi=10.1002/cncr.20312|s2cid=972345 |doi-access=free }}</ref>
* Increase in incidence in the exposed group, such as "each daily alcoholic beverage increases the incidence of breast cancer by 11 cases per 1000 women."<ref name="pmid19244173">{{cite journal  |vauthors=Allen NE, Beral V, Casabonne D, etal |title=Moderate alcohol intake and cancer incidence in women |journal=Journal of the National Cancer Institute |volume=101 |issue=5 |pages=296–305 |date=March 2009 |pmid=19244173 |doi=10.1093/jnci/djn514|doi-access=free }}</ref>
* [[Hazard ratio]], such as "an increase in both total and invasive breast cancers in women randomized to receive estrogen and progestin for an average of 5 years, with a hazard ratio of 1.24 compared to controls."<ref>{{Cite journal | last1 = Heiss | first1 = G. | last2 = Wallace | first2 = R. | last3 = Anderson | first3 = G. L. | last4 = Aragaki | first4 = A. | last5 = Beresford | first5 = S. A. A. | last6 = Brzyski | first6 = R. | last7 = Chlebowski | first7 = R. T. | last8 = Gass | first8 = M. | last9 = Lacroix | first9 = A. | title = Health Risks and Benefits 3 Years After Stopping Randomized Treatment with Estrogen and Progestin | journal = JAMA: The Journal of the American Medical Association | volume = 299 | issue = 9 | pages = 1036–45 | year = 2008 | doi = 10.1001/jama.299.9.1036 | pmid=18319414| url = https://escholarship.org/content/qt4qs7w2fg/qt4qs7w2fg.pdf?t=pu0k9y | doi-access = free }}</ref>

==Example==
At a wedding, 74 people ate the chicken and 22 of them were ill, while of the 35 people who had the fish or vegetarian meal only 2 were ill. Did the chicken make the people ill?

:<math>Risk = \frac {\mbox{number of persons experiencing event (food poisoning)}} {\mbox{number of persons exposed to risk factor (food)}}</math><ref>{{Citation|last1=Tenny|first1=Steven|title=Relative Risk|date=2020|url=http://www.ncbi.nlm.nih.gov/books/NBK430824/|work=StatPearls|publisher=StatPearls Publishing|pmid=28613574|access-date=2020-06-10|last2=Hoffman|first2=Mary R.}}</ref>

So the [[chicken]] eaters' risk = 22/74 = 0.297<br />
And non-chicken eaters' risk = 2/35 = 0.057.

Those who ate the chicken had a risk over five times as high as those who did not, that is, a relative risk of more than five. This suggests that eating chicken was the cause of the illness, but this is ''not'' proof.

This example of a risk factor is described in terms of the [[relative risk]] it confers, which is evaluated by comparing the risk of those exposed to the potential risk factor to those not exposed.

==General determinants==
The probability of an outcome usually depends on an interplay between multiple associated variables. When performing [[epidemiological studies]] to evaluate one or more determinants for a specific outcome, the other determinants may act as [[confounding]] factors, and need to be controlled for, e.g. by [[stratification (statistics)|stratification]]. The potentially confounding determinants varies with what outcome is studied, but the following general confounders are common to most epidemiological associations, and are the determinants most commonly controlled for in epidemiological studies:{{citation needed|date=July 2020}}
* Age (0 to 1.5 years for infants, 1.5 to 6 years for young children, etc.)
* Sex or gender (Male or female)<ref name=":1">{{Cite book|title=Abnormal child psychology|last=Mash, Eric J.|others=Wolfe, David A. (David Allen), 1951-|year=2019|isbn=9781337624268|edition= Seventh|location=Boston, MA|oclc=1022139949}}</ref>{{Rp|20}}
* Ethnicity (Based on race)<ref name=":1" />{{Rp|21}}

Other less commonly adjusted for possible confounders include:
* Social status/income<ref name=":0" />{{Rp|39}}
* Geographic location
* Genetic predisposition
* Gender identity
* Occupation
* [[Overwork]]<ref>{{cite journal |last1=Pega |first1=Frank |last2=Nafradi |first2=Balint|last3=Momen |first3=Natalie |last4=Ujita |first4=Yuka |last5=Streicher |first5=Kai |last6=Prüss-Üstün |first6=Annette |last7=Technical Advisory Group |title=Global, regional, and national burdens of ischemic heart disease and stroke attributable to exposure to long working hours for 194 countries, 2000–2016: A systematic analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury |journal=Environment International |date=2021 |volume=154 |page=106595 |doi=10.1016/j.envint.2021.106595|pmc=8204267  |issn=0160-4120 |pmid=34011457 |doi-access=free |bibcode=2021EnInt.15406595P }}</ref>
* Sexual orientation
* Level of [[chronic stress]]
* Diet
* Level of [[physical exercise]]
* Alcohol consumption and [[tobacco smoking]]
* Other [[social determinants of health]]

==Risk marker==
A ''risk marker'' is a variable that is quantitatively associated with a disease or other outcome, but direct alteration of the risk marker does not necessarily alter the risk of the outcome. For example, driving-while-intoxicated (DWI) history is a risk marker for pilots as epidemiologic studies indicate that pilots with a DWI history are significantly more likely than their counterparts without a DWI history to be involved in aviation crashes.<ref>Li G., Baker S. P., Qiang Y., Grabowski J. G., McCarthy M. L. Driving-while-intoxicated history as a risk marker for general aviation pilots. Accid Anal Prev. 2005;37(1):179-84./McFadden K. L. Driving while intoxicated (DWI) convictions and job-related flying performance – a study of commercial air safety. J Oper Res Soc. 1998;49:28–32</ref>

==History==
The term "risk factor" was coined by former [[Framingham Heart Study]] director, [[William B. Kannel]] in a 1961 article in ''[[Annals of Internal Medicine]]''.<ref>{{cite news|title=William Kannel, Former Director of the Framingham Heart Study, Dead at 87| url=https://www.forbes.com/sites/larryhusten/2011/08/23/william-kannel-former-director-of-the-framingham-heart-study-dead-at-87/ | work=Forbes | first=Larry | last=Husten | date=23 August 2011}}</ref>

==See also==
* [[Health risk assessment]]
* [[Protective factor]]
* [[Risk factor (finance)]]
* [[Social determinants of health]]

==References==
{{reflist|30em}}

==Further reading==
* S. P. Case; K. R. Haines (2009). ''Understanding Youth Offending: Risk Factor Research, Policy and Practice''. Willan. 2009. {{isbn|9781843923428}}.
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[[Category:Medical statistics]]
[[Category:Risk factors| ]]