DESCRIPTIVE%20EPIDEMIOLOGY%20for%20Public%20Health%20Professionals%20Part%204

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DESCRIPTIVE EPIDEMIOLOGYfor Public Health
Professionals Part 4

• Ian R.H. Rockett, PhD, MPH
• Department of Community Medicine
• West Virginia University School of Medicine

Prepared under the auspices of the Southeast
Public Health Training Center, University of
North Carolina, Chapel Hill, 2005.
irockett_at_hsc.wvu.edu
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• From MEASUREMENT
  to
  DESCRIPTION

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Descriptive Epidemiology

• Magnitude of the Problem - how big?
• Person, Place, and Time
• - who, where, and when?

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Magnitude of the Problem
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Injury Deaths Worldwide by Leading Causes and
Intent, 1990
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Person Place and Time
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PERSON

• Demographic characteristics e.g. age, sex, race,
  marital status, number of children
• Socioeconomic characteristics e.g. social
  class, employment status, occupation
• Life style/behavior e.g. drinking
  alcohol/smoking marijuana and driving

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United States Suicide Rates by Age, Sex, and
Racial Group, 1999-2001
Data accessed through CDC Wonder
http//wonder.cdc.gov/mortICD10J.html
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PLACE

• Are the disease or injury cases
• geographically confined or pervasive?
• clustering around known potential pathogens,
  toxins, or other hazards?

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TIME

• Are disease (injury) rates or case numbers
  variable or constant?
• Do rates or case numbers vary seasonally?
• Is the disease attributable to a point source of
  infection or propagated transmission?

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Source McAuley, J. et al. A Trichinosis
Outbreak Among Southeast Asian Refugees (1992).
American Journal of Epidemiology
135(12)1404-1410. Reproduced in Rockett, I.R.H.
Population and Health An introduction
toEpidemiology(1999). Population Bulletin
54(4)23.
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Descriptive Study Designs
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• Correlational (Ecological) Study uses data from
  entire populations to compare disease/injury
  frequencies in relation to putatively harmful
  (or beneficial) exposures during the same
  period of time or at different points in time
  (typically use secondary published data like
  vital statistics, censuses and national health
  surveys)

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Source Len Evans. Traffic Crashes. American
Scientist 90 (3) 2002 246. http//www.dushkin.co
m/text-data/articles/34749/body.pdf
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• Case Report - most basic type of descriptive
  study of individuals, comprising a careful
  detailed report by one or more clinicians that
  profiles a single patients case

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• Case Series describe characteristics of a
  number of patients with a given disease

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• Cross-Sectional Studies
• the status of an individual with respect to the
  presence or absence of both exposure and
  disease/injury of interest is assessed at one
  point in time (if the timing of each cannot be
  differentiated, this too qualifies a study as
  cross-sectional)

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• HYPOTHESIS FORMULATIONThe Bridge
  to Analytic
  Epidemiology

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Method of Difference

• Examines differences among groups for clues as to
  why the groups disease rates or other health
  problems vary

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Source Ian R.H. Rockett. Population and Health
An Introduction to Epidemiology. Second edition.
Population Bulletin 54(4) 1999 17.
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Method of Agreement

• Looks for commonality in groups that manifest the
  same health problem

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Method of Concomitant Variation

• Traces how exposure to a hazard varies in
  relation to disease or other health problems

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Problem of Chronic Disease Latency
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Source Doll, R. Etiology of Lung Cancer (1955).
Advances in Cancer Research 319551-50.
Reproduced in I.R.H. Rockett. Population and
Health An introduction to Epidemiology, Second
edition. Population Bulletin,54(4)1999 25.

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Early Intervention in the Natural History of
Disease
HEALTH OUTCOMES Cure Control Disability Death
Good Health
Disease Onset
Care Seeking
Symptoms
Diagnosis
Therapy
Early detection through Screening
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Method of Analogy

• Involves applying a model that characterizes one
  kind of disease or injury to another kind

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Method of Detection of Conflicting Observations

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Pellagra, commonly regarded as a communicable
disease, produced skin eruptions and digestive
and nervous disorders

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Joseph Goldberger, 1874-1929

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Laboratory Observations
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Even though lacking research experience, Dr.
Barry Marshall and Dr. Robin Warren were able to
link peptic ulcers to the bacterium Helicobacter
Pylori
Source University of Western Australia. UniView
22(1)20034.
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ANALYTIC EPIDEMIOLOGY

• Addressing the why question

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From Epidemiology to Population Health
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Years of Healthy Life vs. Years of Life, United
States, 1990
Years
Age (in years)
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To Access Some Online Epidemiology Texts

• Visit
• http//www.epidemiolog.net/evolving/
• TableOfContents.htm
• http//www.prb.org/Template.cfm?SectionPopulatio
  n_Bulletin1template/ContentManagement/ContentDis
  play.cfmContentID9854
• http//bmj.com/epidem/epid.html