Transcript DESCRIPTIVE EPIDEMIOLOGY for Public Health Professionals Part 2 Ian R.H. Rockett, PhD, MPH Department of Community Medicine West Virginia University School of Medicine Prepared under the.

DESCRIPTIVE EPIDEMIOLOGY
for Public Health Professionals
Part 2
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.
[email protected]
DISEASE
and
INJURY MODELS
The Epidemiologic Triad
HOST
AGENT
ENVIRONMENT
Factors involved in the Natural History of Disease
Agent
Vector
Host
Environment
Epidemiologic Triad applied to Injury
Levels of Prevention
 Primary
 Secondary
 Tertiary
The Haddon Matrix
Physical
Sociocultural
Factors Human Agent
Environment Environment
Factors
or
Phases
Vehicle
Preevent
Event
Postevent
Source: Ian R.H. Rockett. Injury and Violence: A Public Health Perspective. Population
Bulletin 53(4); 1998: 18. Adapted from G.S Smith and H. Falk, Unintentional Injuries.
American Journal of Preventive Medicine 3(5) Supplement; 1997:143-163.
Haddon Matrix (bombings)
Factors
Person
Physical
Environ.
Social
Environ.
(bomb /
bomber)
Phases
Pre-event Teach to
recognize
suspicious
persons
Wear
Event
(explosion & protective
clothes
collapse
Postevent
Vehicle/
Vector
Train people
in first aid
Detectable No vehicle
zones
bombs
Reduce
animosity
Slower
acting
explosives
Strengthen
norms for
rescue
volunteers
Strengthen
public health
infrastructure
??
Shatterproof glass
Emergency
call boxes
The Wheel of Causation
Social
Environment
Biological
Environment
Host
(human)
Genetic Core
Physical
Environment
Web of Causation
-- de-emphasizes the disease
agent and allows for
multifactorial causes
Web of Causation applied to Myocardial Infarction
Wider Application of the Web
Epidemiologic Triad (devised to
enhance search for understanding
communicable disease)
Web of Causation (devised to
address chronic disease – can also
be applied to communicable disease)
DATA SOURCES
and
DEVELOPMENT
of
INFORMATION
Natural History of Disease/Injury
and Related Data Sources
Good
Health
Disease
Onset
Symptoms
Screening
Test Results
Care Diagnosis Therapy
Seeking
HEALTH
OUTCOMES
Cure
Control
Disability
Death
Interviews
SELECTED
DATA
SOURCES
Medical Records
Hospital/ED Records
Death Certificates
Medical Examiner
aaaaRecords
Mortality (Death)
Records
Source: Leon Gordis, Epidemiology, 2d edition; Philadelphia,
PA: Saunders, 2000: 50.
Uncertainty in Reported Cause of Death
1)
2)
3)
4)
Michael Alderson (1988) identified four
areas where uncertainties or inaccuracies
can arise in reporting causes of death:
incorrect diagnosis (last attending
physician and/or autopsy)
incorrect completion of death certificate
inaccurate processing and publication of
the mortality statistics
invalid classification of diseases/injuries
Multiple
Cause-of-Death
Analysis
Distinguishing Natural
from Other Causes of
Death
Use of Medical Examiner
and Coroner Records to
supplement Death
Certificate Data
Need to rule out homicide, suicide or “accident” ,
i.e., unintentional injury, before a death can be validly
attributed to natural causes.
Homicide or SIDS?
Disease and Injury Mortality are only the Tip
of the Iceberg
Morbidity Data
Sources
General Sources of Morbidity Data
1. Disease reporting -- communicable diseases, cancer
registries
2. Data accumulated as a by-product of insurance and
prepaid medical care plans
a. Group health and accident insurance
b. Prepaid medical care plans
c. State disability insurance plans
d. Life insurance companies
e. Hospital insurance plans
f. Railroad Retirement Board
3.
a.
b.
c.
d.
Tax-financed public assistance and medical care plans
Public assistance, aid to the blind, aid to the disabled
State or federal medical care plans
Armed Forces
Veterans Administration
General Sources of Morbidity
Data continued. . .
4. Hospitals and clinics
5. Absenteeism records -- industry and schools
6. Pre-employment and periodic physical
examinations in industry and schools
7. Case-finding programs
8. Selective service records
9. Morbidity surveys on population samples (e.g.,
National Health Survey, National Cancer Surveys)
Source: Leon Gordis. Epidemiology. Third edition. Philadelphia, PA, 2004: 37.
ICD and ICD-CM
 The International Statistical Classification of
Diseases and Related Health Problems (ICD)
can be used for coding and classifying
mortality data from death certificates
 The International Classification of Diseases
Clinical Modification (ICD-CM) can be used to
code and classify disease and injury
morbidity data from inpatient and outpatient
records
Dynamic Classification
Causes of disease, injury and
disability may wax and wane. ICD
needs to be flexible, especially in
responding to new circumstances:
e.g. SARS, terrorism attributable health
outcomes as from such varied causes as
asphyxiation, chemical burns, falls and
jumping from buildings, and suicide and
suicide attempts
Primary data are new data
collected by or for the
investigator
Secondary data refer
to existing data
Stages of Development of
Information
1) Public health surveillance –
development and refinement of data
systems for the ongoing and
systematic collection, analysis,
interpretation and dissemination of
information
Stages of Development of
Information
2) Risk group identification –
identification of persons at greatest
risk of disease or injury and the
places, times, and other
circumstances that are associated
with elevated risks
Stages of Development of
Information
3) Risk factor identification – analytic
exploration of potentially causative
risk factors for disease, injury or
death as suggested by the high risk
population and other research
Stages of Development of
Information
4) Program development, implementation,
and evaluation – design, implementation
and evaluation of preventive interventions
based on degree of understanding of the
population-at-risk and the risk factors for
the outcome of interest
A Caveat on Data Quality
(“garbage in - garbage out”)
The government is very keen on amassing
statistics. They collect them, add them,
raise them to the nth power, take the cube
root and prepare wonderful diagrams. But
you must never forget that every one of
these figures comes in the first instance
from the village watchman, who just puts
down what he damn well pleases.
Sir Josiah Stamp, British
Economist (1880-1941)