Risk Epidemiology

8/9/2019 Risk Epidemiology

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%b&ectivesDefine easures of absolute, relative andattributable risk

Identify a&or e'ide iolo$y study desi$ns

(sti ate absolute, relative and attributablerisks fro studies in t"e e'ide iolo$yliterature

Inter'ret risk esti ates for 'atients and

a''ly t"e in clinical 'ractice


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)linical ('ide iolo$y isScience of akin$ 'redictions about individual'atients by countin$ clinical events in si ilar'atients, usin$ stron$ scientific et"ods forstudies of $rou's of 'atients to ensure t"at'redictions are accurate

I 'ortant a''roac" to obtainin$ t"e kind ofinfor ation clinicians need to ake $ooddecisions in t"e care of t"eir 'atients

Sounds like evidence based 'ractice*

+letc"er, +letc"er -a$ner, .//


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)onsiderations!atient1s 'ro$nosis is e 'ressed as'robabilities 3 esti ated by 'aste 'erience

Individual clinical observations can besub&ective and affected by variables t"atcan cause isleadin$ conclusions

)linicians s"ould rely on observations basedon investi$ations usin$ sound scientific'rinci'les, includin$ 4ays to reduce bias

+letc"er, +letc"er -a$ner, .//


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('ide iolo$y is!rocess by 4"ic" 'ublic "ealt" 'roble sare detected, investi$ated, and analy5ed3 Risk esti ates

6ased on lar$e 'o'ulations, not 'atients ort"eir care$ivers

3 !otential bias and confoundin$ are a&orissues to be considered

Scientific basis of 'ublic "ealt"


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%b&ectives of ('ide iolo$yo deter ine t"e rates of disease by 'erson,

'lace and ti e3 Absolute risk 8incidence, 'revalence9

o identify t"e risk factors for t"e disease3 Relative risk 8or odds ratio9

o develo' a''roac"es for disease 'revention3 Attributable risk:fraction


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o identify t"e risk factors for

t"e diseaseRelative risk 8RR9, odds ratio 8%R93 RR ; ratio of incidence of disease in e 'osed

individuals to t"e incidence of disease innon


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o identify t"e risk factors for

t"e diseaseRelative risk 8RR9, odds ratio 8%R93 RR ; ratio of incidence of disease in e 'osed

individuals to t"e incidence of disease innon


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o develo' a''roac"es for

disease 'reventionAttributable risk 8AR9:fraction 8A+93 AR ; t"e a ount of disease incidence t"at

can be attributed to a s'ecific e 'osure=Difference in incidence of disease bet4eene 'osed and non


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Attributable Risk( cess

Risk

Risk +actor

Risk

AR ; Risk a on$ riskfactor 'ositives

Risk a on$ riskRisk a on$ riskfactor ne$ativesfactor ne$atives


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--

Attributable +raction

Risk a on$risk factor'ositives

A+ ;

Risk a on$risk factorne$atives

Risk a on$risk factor'ositives

@ .00


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Ma&or ('ide iolo$y Study

Desi$ns)ase )ontrol 8retros'ective9

)o"ort 8'ros'ective9

)ross sectional 8one 'oint in ti e9


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No

Disease

Disease

No

Disease

Disease

Riskfactor -

Riskfactor+

Riskfactor -

Riskfactor+

)ase )ontrol:Retros'ective

Studies Identifyaffected andunaffectedindividuals

Risk factordata iscollectedretros'ectively


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)ase )ontrol:Retros'ective

StudiesAdvanta$es3 Ine 'ensive

3 Relatively s"ort3 Good for rare

disorders3 Measures of risk

=%dds ratio=Attributable risk

8if incidence iskno4n9

Disadvanta$es3 Selection of

controls can bedifficult3 May "ave biased

assess ent of

e 'osure3 )annot establis"cause and effect


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Risk

factor -

Risk

factor+

Risk

factor -

Risk

factor+

No

Disease

Disease

No

Disease

Disease

)o"ort:!ros'ective Studies

Identifyunaffectedindividuals

Risk factordata collectedat baseline

+ollo4 untiloccurrence of

disease


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)o"ort:!ros'ective Studies

Advanta$es3 (stablis"es cause

and effect3 Good 4"en disease

is freBuent3 #nbiased

assess ent ofe 'osure

3 Measures of risk=Absolute risk

8incidence9=Relative risk=Attributable risk

Disadvanta$es3 ( 'ensive3 Car$e

3 ReBuires len$t"yfollo4


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)o"ort and )ase )ontrol

Studies

Risk factor? Disease?

Risk factor? Disease?

Case-Control Studies

Cohort Studies

Past Present Future


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)ross Sectional Studies

Determine presence of disease and riskfactors at the same time – “snapshot”

Defned Population

Risk Factor+

Risk Factor -

Nodisease Nodisease Disease Disease


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)ross Sectional Studies

Advanta$es3 Assess ent of

disease:riskfactors at sa eti e

3 Measures of risk=Absolute risk8'revalence9=%dds ratio=Attributable risk

8if incidence iskno4n9

Disadvanta$es3 May "ave biased

assess ent ofe 'osure3 )annot establis"

cause and effect


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Inter'retin$ Study ResultsNo suc" t"in$ as a 'erfect1 studyReco$ni5e t"e li itations and t"estren$t"s of any one study)ritiBuin$ t"e e'ide iolo$y literatureEAre t"ey co 'arable in ter s of de o$ra'"ic

and ot"er c"aracteristicsFAre t"ey re'resentative of t"e entire'o'ulationFAre t"e easure ent et"ods co 'arable8e $ , eli$ibility and classification criteria, riskfactor assess ent9F)ould associations be biased or confounded byot"er factors t"at 4ere not assessedF


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Genetic ('ide iolo$yof y'e . Diabetes

( a 'le of assessin$absolute, relative andattributable risks


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y'e . Diabetes%ne of ost freBuent c"ronic c"ild"ood diseases3 !revalence H 2:.000 in Alle$"eny )ounty3 Incidence H 20:.00,000:yr in Alle$"eny )ounty

Due to autoi une destruction of 'ancreatic cells3 (tiolo$y re ains unkno4n

('ide iolo$ic researc" ay 'rovide clues3 ./7/ 3 be$an study at !itt, GS!


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y'e . Diabetes Re$istries)"ildren1s os'ital of !ittsbur$" Re$istry3 All .D cases seen at ) ! diabetes clinic

since ./K03 May not be re'resentative of all ne4ly

dia$nosed cases

Alle$"eny )ounty y'e . Diabetes Re$istry3 All ne4ly dia$nosed 8incident9 .D cases in

Alle$"eny )ounty since ./ K


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y'e . Diabetes Incidence

Alle$"eny )ounty, !A


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(vidence for (nviron ental

Risk +actorsSeasonality at onsetIncrease in incidence 4orld4ideMi$rants assu e t"e risk of "ostcountry(nviron ental risk factors< May act as initiators or 'reci'itators< Liruses, infant nutrition, stress


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(vidence for Genetic

Risk +actorsIncreased risk for .st de$reerelatives3 Risk for siblin$s H

)oncordance in M t4ins 20 < K0Stron$ly associated 4it" $enes in t"e

CA re$ion of c"ro oso e 3 DR6


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!pe " Dia#etes Re$istries – %&+ Countries #!"'('


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-"at is )ausin$ t"e Geo$ra'"icDifference in .D Incidence

(nviron ental risk factors

Susce'tibility $enes3More t"an 20 $enes associated 4it" .D3 CA re$ion 3 c"ro oso e is ost i 'ortant


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CA


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- % DiaMond Molecular

('ide iolo$y Sub


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Susce'tibility a'loty'es

for y'e . DiabetesDR6.< D A.< D 6. (t"nicity

O0P0K


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Distribution of Genoty'es

S ; D A.


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%dds Ratios for .D!o'ulation 2S .S+inland K. O .0 2O

!A


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o4 to (sti ate Genoty'e<

S'ecific Incidence fro a)ase )ontrol StudyF

for individuals 4it" 2S, .Sand 0S $enoty'es


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%verall !o'ulation Incidence

8R9Is an avera$e of t"e $enoty'e


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R ; !o'ulationincidence

R2S , R.S , R0S ; Genoty'e<s'ecific

incidence

! 2S, ! .S , ! 0S ; Genoty'e'ro'ortions

a on$ controls

R ; R2S ! 2S R.S ! .S R0S ! 0S?? ?? ??


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%dds Ratios A''ro i ate

Relative Risks 8RR9%R2S ≈ RR2S ; R 2S : R 0S

%R.S ≈ RR.S ; R .S : R 0S

%R0S ≈ RR0S ; R 0S : R 0S


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R ; R2S! 2S R.S ! .S R0S! 0S

)an be re


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%R2S ≈ R2S : R 0S< %R2S and R0S are kno4n,

Solve for R2S

%R.S ≈ R.S : R 0S< %R.S and R0S are kno4n,

Solve for R .S

R ; R2S! 2S R.S ! .S R0S! 0S

R 4as used to esti ate cu ulative incidencerates t"rou$" a$e QK years 8R QK9 so risk

esti ates could be inter'reted as 'ercents


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Absolute .D Risks "rou$"

A$e QK Vrs!o'ulation 2S .S+inland 7 . 2 Q

!A


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Attributable +raction for

.D 3 !ublic ealt" I 'lications!o'ulation 2S+inland 2/

!A


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Absolute Risk 8Incidence9

Does not indicate 4"et"er t"ere is asi$nificant 'ositive or ne$ative association

May be ore i 'ortant t"an odds ratio,'articularly 4"en t"ey can be esti ated asa 'ercent

as i 'ortant clinical i 'lications forindividuals and 'ractitioners


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Genetic Information forTesting Type 1 Diabetes

GIFT-D

Developing andevaluating a theory-based web education

and riskcommunicationprogram for familieswith T1D


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T1D Risk lgorithm

A 1% year old child $hoshares both D#haplotypes $ith her T1Dsister has a &'( chanceof de)eloping T1D byage *+ years if neither

parent has T1D

Risk increases to &*,( if both parents ha)e T1D

(ncoura$e you to use $enetic


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(ncoura$e you to use $enetice'ide iolo$ic literature to

esti ate absolute, relative andattributable risk

I 'ortant for evidence

based nursin$ 'ractice int"e 'ost


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"ank you*


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References

Dor an JS and 6unker ) CA


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References

+letc"er R , +letc"er S-, -a$ner ()linical e'ide iolo$yE t"e essentials,

Ci''incott -illia s and -ilkins, .//

Gordis C ('ide iolo$y -6 Saunders )o ,!"iladel'"ia, .//

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Risk Epidemiology

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