CH04 PP Epidomology

8/17/2019 CH04 PP Epidomology

1/42

Chapter 4

Descriptive Epidemiology:

Patterns of Disease—Person, Place,Time


2/42

Learning Objectives

• Define the term descriptive epidemiology• Discuss types of descriptive epidemiologic studies

and their uses

• Describe the process of epidemiologic inference inthe context of descriptive epidemiology• Give t o examples each of person, place, and time

variables and describe ho they relate to the

distribution of health outcomes


3/42

Introduction

• !ne"ual distributions of health and disease in populations

• To determine hy health conditions varythroughout populations, one must ans er thefollo ing "uestions:

# $ho as affected% # $here did the &health' event occur% # $hen did the &health' event occur%


4/42

Definition: DescriptiveEpidemiology

• The field of descriptive epidemiology classifies theoccurrence of disease according to the follo ingvariables: # person & ho is affected' # place & here the condition occurs' # time & hen and over hat time period the condition has

occurred'


5/42

Descriptive Epidemiologic tudy

• ( descriptive epidemiologic study is onethat is )***concerned ith characteri+ing the

amount and distribution of health anddisease ithin a population*


6/42

Descriptive Epidemiology

• Provides valuable information for thefollo ing activities: # Prevention of disease # Design of interventions # -onduct of additional research


7/42

E!ample of a DescriptiveEpidemiologic tudy

• !*.* infants born in /001 ho ere exclusively breastfed: # (bout 203 of infants ere breastfed during first three

months of life* # (bout 443 ere breastfed through the age of six

months* # 5rom descriptive information, hypotheses for

interventions to increase breastfeeding can be derived*


8/42

"ses of Descriptive Epidemiologic

tudies

• Permit evaluation of trends in health and disease

• Provide a basis for planning, provision, andevaluation of health services

• 6dentify problems to be studied by analyticmethods and suggest areas that may be fruitful forinvestigation


9/42

#ypes of Descriptive Epidemiologictudies

• -ase reports• -ase series• -ross7sectional studies


10/42

Case $eports

• (ccounts of a single occurrence of a note orthyhealth7related incident or of a small collection ofsuch events

• Example: (dverse reactions due to cosmetic surgeryin the !nited .tates


11/42

Case eries

• 6n comparison ith a case report, a case series is alarger collection of cases of disease, often groupedconsecutively and listing common features, e*g*

characteristics of affected patients*• Example: reported cases of primary

meningoencephalitis &4/4 cases reported bet een4829 and /009'


12/42


13/42

Cross% ectional tudies

• ( type of investigation ) that examines therelationship bet een diseases &or other health7related characteristics' and other variables of

interest as they exist in a defined population at one particular time*

• ( type of prevalence study

• Example: the ;ehavioral


14/42

Epidemiologic Inferences from

Descriptive Data• Descriptive epidemiology and descriptive studies

provide a basis for generating hypotheses*• Descriptive epidemiologic studies connectintimately ith the process of epidemiologicinference*

• Epidemiologic inference is initiated ithdescriptive observations*


15/42

&erson 'ariables: E!amples

• (ge• .ex

• Ethnicity• .ocioeconomic .tatus

• ?arital .tatus• @ativity &place of

origin'• ?igration•


16/42

(ge

• Perhaps the most important factor to considerhen describing occurrence of disease or illness

) (ge7specific disease rates usually sho greatervariation than rates defined by almost any other

personal attribute*


17/42

E!amples of (ge (ssociations

• The incidence of and mortality from chronicdiseases increase ith age*

• .ome infections, e*g*, mumps and chic=enpox occurmore commonly during childhood*

• The leading cause of death among young adults isunintentional inAuries*

• ?aternal age is associated ith rates of diabetes andrelated complications*


18/42

e!

• Epidemiologic studies have sho n sex differencesin a ide scope of health phenomena includingmorbidity and mortality*

• Examples: ) (ll cause age7specific mortality rates higher among

males ) Differences in cancer rates, e*g*, cancers of the genital

system


19/42

(ge%adjusted invasive cancer incidence rates per*++,+++ for the *+ primary sites -ith the highest

rates -ithin race% and ethnic%specific categories.

Source: (dapted and reprinted from !*.* -ancer .tatistics $or=ing Group* United States Cancer Statistics: 2003 Incidence and Mortality * (tlanta: !*.* Department of Bealth and Buman .ervices, -enters for Disease -ontroland Prevention and @ational -ancer 6nstituteC /00 ://0 and ///*


20/42

$ace/Ethnicity

• 5ive maAor categories in -ensus /000: ) $hite ) ;lac= or (frican (merican

) (merican 6ndian and (las=a @ative ) (sian ) @ative Ba aiian and other Pacific 6slander

• -ensus /000 allo ed respondents to chec= amultiracial category*


21/42

$acial/ethnic distribution of the populationof the "nited tates, 0++1 estimates. Datafor individuals -ho declare only one race.

Source: (uthor* Data from !*.* -ensus ;ureau* 5act .heet: /00 (merican -ommunity .urvey

Data Profile Bighlights* (vailable at: http:>>factfinder*census*gov>servlet>(-..(555acts*(ccessed (ugust 4 , /00F*


22/42

$ace/Ethnicity:

Other Considerations

• .ome hat ambiguous classification

• Tends to overlap ith nativity and religion• .ome scientists propose that it is a social

construct rather than a biological construct*

• !sed to trac= various health outcomes


23/42

2ativity

• Place of origin of the individual or his or herrelatives ) .ubdivisions include:

• 5oreign7born• @ative7born


24/42

$ace/Ethnicity 3cont.

• Examples of racial>ethnic differences in healthcharacteristics include the follo ing: ) o er fre"uency of asthma reported among Bispanics*

) @on7Bispanic hites and non7Bispanic blac=s lessfre"uently report that they have no usual source ofmedical care than Bispanics*

) 6ncidence of gonorrhea is higher among non7Bispanic blac=s than other groups*


25/42

ocioeconomic tatus 3 E

• Defined as a )Descriptive term for a personHs position in society,

• Iften formulated as a composite measure of thefollo ing dimensions: ) ( personHs income level ) Education level

) Type of occupation• ( single dimension of .E. &e*g*, poverty level' may

be used*


26/42

ocioeconomic tatus 3 E 3cont.

• The social class gradient ) .trong, inverse association of .E. ith levels of

morbidity and mortality

) Those in lo est .E. positions are confronted ithexcesses of morbidity and mortality from numerouscauses*

• Example: access to dental care &see 5igure 1740'


27/42

2o dental visit inthe past year

among persons-ith natural teeth,

by age and

percent of povertylevel: "nitedtates, 0++5.


28/42

Definition: 6ealth Disparities

• Differences in the occurrence of diseases andadverse health conditions in the population # Example: cancer health disparities — ) adverse

differences in cancer incidence &ne cases', cancer prevalence &all existing cases', cancer death&mortality', cancer survivorship, and burden ofcancer or related health conditions that exist amongspecific population groups in the !nited .tates*

# (frican (mericans &in comparison ith other groups'have the highest age7adAusted overall cancerincidence and death rates*


29/42

&lace 'ariables

• 6nternational• @ational & ithin7country'• !rban7rural differences• ocali+ed patterns of disease


30/42

International

• $orld Bealth Irgani+ation &$BI' studies: ) ;oth infectious and chronic diseases sho great

variation from one country to another*

• -limate, cultural factors, national dietary habits,and access to health care affect diseaseoccurrence*

• Jariations in life expectancy &!*.* ran=ednumber 19 in /00F'*

• $ild poliovirus is endemic in parts of (sia and(frica &/00 data'*


31/42


32/42

2ational 37ithin%Country

•


33/42


34/42

"rban%$ural Differences

• !rban and rural sections of the !nited .tates shovariations in morbidity and mortality related toenvironmental and lifestyle issues*

) !rban example: elevated occurrence of lead poisoningamong children ho live in older buildings*

)


35/42

Locali8ed &atterns of Disease

• (ssociated ith specific environmental conditionsthat may exist in a particular geographic area*Examples:

) -ancer and radon gas ) @aturally occurring arsenic in ater supply ) Presence of disease vectors: Dengue fever along the

Texas7?exico border


36/42

#ime 'ariables

• .ecular trends• -yclic &seasonal' trends• Point epidemics• -lustering


37/42

ecular #rends

•


38/42

Cyclic 3 easonal #rends

• -yclic trends are increases and decreasesin the fre"uency of a disease or other

phenomenon over a period of severalyears or ithin a year* # Example 4: severe eather events in

the (tlantic basin*

# Example /: mortality from pneumoniaand influen+a &pea=s during 5ebruary'*


39/42

&oint Epidemics

• ( point epidemic may indicate the response of agroup of people circumscribed in place to a commonsource of infection, contamination, or other etiologicfactor to hich they ere exposed almostsimultaneously* # Example: outbrea= of Vibrio infections follo ing

Burricane Latrina in /00


40/42

Clustering

• )( closely grouped series of events or cases of adisease or other health7related phenomena ith ell7defined distribution patterns in relation to time or

place or both *


41/42

Clustering 3cont.

• Iften used to describe aggregation of uncommonconditions such as leu=emia*

• -lustering may reflect: # -ommon exposure to an etiologic agent # -hance occurrences

• .patial clustering—refers to aggregation ofevents in a geographic region*

• Temporal clustering—denotes the occurrence ofevents related to time*


42/42

Conclusion

• Descriptive epidemiology classifies theoccurrence of disease according to the variablesof person, place, and time*

• Descriptive epidemiologic studies aid ingenerating hypotheses that can be explored byanalytic epidemiologic studies*

• Descriptive studies include case reports, casestudies, and cross7sectional studies*

Documents

CH04 PP Epidomology