Descriptive Epidemiology Knight Fellowship

1
Descriptive Epidemiology(Knight Fellowship)
By Philip S. Brachman, MD
June, 2006
2
EPI DEMOS LOGOS Upon People Study
The study of anything that happens to people
3
Epidemiology is
the dynamic study of the determinants,
occurrence, distribution and control of health
and disease in a population
4
Epidemiology is
the study of the patterns of disease occurrence
5
Epidemiology
identifies the risk factors
6
Epidemiology
defines the relationship of disease to the
population at risk
7
Clinician Epidemiologist Patients
diagnostician Communitys
diagnostician Hx, P.E., Lab. (PT) Hx, P.E.,
Lab. (PTS) Diagnosis Predict
trend Therapy Control Cure Prevention
8
Uses of Epidemiology

• Describes health events
• Identify cause of disease
• Identify risk factors
• Describe the clinical pattern of disease
• Identify syndromes
• Identify control and/or preventive measures

9
Kinds of Epidemiology

• Descriptive
• Analytic
• Experimental

10
Descriptive Epidemiology
Study of the occurrence and distribution of
disease Terms Time Place Person
11
Time
Secular Periodic Seasonal
Epidemic
12
Secular Trend
The long-time trend of disease occurrence
13
Tetanus by year, United States, 1955-2000
During 2000, a total of 35 cases of tetanus were
reported. The percentage of cases among persons
aged 25-59 years Has increased in the last
decade. Note A tetanus vaccine was first
available in 1933.
Reported Cases
14
Malaria by year, United States 1966-2001
Returning Vietnam Veterans
Foreign immigration from Malaria- endemic
countries
Reported Cases per 100,000 Population
Imported malaria cases have increased over the
last 15 years, most likely as a result of
increasing international travel and immigration
and growing antimalarial drug resistance.
15
Periodic Trend
Temporal interruption of the general trend of
secular variation
16
Whooping Cough - Four-monthly admissions,
1954-1973
17
Number of reported pertussis cases, by year,
United States, 1922-2000
18
Meningococcal Infection By year, United States,
1935-1992
19
Rabies Wild and domestic animals, by year,
United States and Puerto Rico, 1973-2003
20
Seasonal Trend
21
Pneumonia-Influenza Deaths By year, 1934-1980
22
Epidemic
An increase in incidence above the expected in a
defined geographic area within a defined time
period
23
Clinical Rubella cases in high school B, by date
of onset, Stark County, Ohio, March June 1975
24
Cholera cases, Port Lavaca, Texas, 1900-1973
25
Place
Where patient was exposed or Where source became
infected
26
Place
Geographic Area Example
Action Level
Investigation Control Prevention
Diagnosis is Made Contact occurred between agent
and host Source became infected
Home Patient Ill Restaurant Food
Eaten Farm Eggs Infected
27
(No Transcript)
28
Deaths from Cholera per 10,000 houses by source
of water supply, London 1854
Number of Deaths from
Deaths in
Houses Cholera each Water
Supply 10,000 homes
Southwark Vauxhall 40,046 1,263
315 Company Lamberth Company 26,107
98 37 Rest of London
256,423 1,422 59
29
Deaths due to nasal cancer (ICDA 160), white
males, ages 65 and over, 1972-1974
30
Distribution of facilities where workers are
potentially exposed to formaldehyde (in 10 or
more of the workforce)
31
Person
Age Hobbies Sex Pets Occupation Trave
l Immunization status Personal
Habits Underlying disease Stress Medication F
amily unit Nutritional status School Socioeconom
ic factors Genetics Crowding Religion
32
Analytic Epidemiology
Further studies to determine the validity of a
hypothesis concerning the occurrence of disease.
33
Examine the relationship between
Cause Effect
Factors Disease
34
Analytic Epidemiology
Past Present Future
Case-control CAUSE EFFECT Cohort
CAUSE EFFECT
35
Case-Control
Study those affected with disease and for
comparison use a control group similar in all
known ways except for the presence of the disease
itself
Past Present CAUSE EFFECT Blood
Product Hepatitis
36
Cohort
Study those exposed and not exposed to a cause to
see the effects of that cause
Present Future Cause Effect Blood
Product Hepatitis
37
Cross-Sectional
The measurements of cause and effect are made at
the same time which allows direct measurement of
the variables.
38
Cross-Sectional
Limited to studies of causes that are reasonably
permanent characteristics of the individual so
that cause and effect are present at the same
time.
39
Cross-Sectional
Describes prevalence relationships not incidence
40
Prevalence

• the number of cases of a disease occurring in a
  specified population at a designated time.
• Point prevalence at a specific point in time
• Period prevalence over a specific period of
  time

41
Incidence

• the number of onsets of new cases of a disease
  occurring in a specified population in a
  specified time period

42
July 1 August 1
43
Experimental Epidemiology
Manipulate Cause Effect Deliberate
manipulation of the cause is predictably followed
by an alteration in the effect not due to chance.