Lecture 1 INTRO TO EPI.ppt Lecture 1 INTRO TO EPI.ppt

Lecture 1 INTRO TO EPI.ppt

1. Epidemiology & Demography
BCM 317
Lecture 1

2. Objectives
•Define epidemiology
•Define demography
•Discuss historical developments in
epidemiology
•Describe theories of causation
•Define epidemic, endemic and pandemic

3. Epidemiology
•EPI - on, upon
•DEMOS- people
•LOGOS- study
“The study of that which falls upon the
people”

4. Definition of epidemiology
A practical/working definition:
The study of the distribution and
determinants of disease frequency in
(human) populations
McMahon and Pugh, 1970

5. Definition of epidemiology
A broader and widely accepted definition:
The study of the distribution and determinants
of health-related states or events in specified
populations, and the application of this study to
the control of health problems and health
promotion
Last JM(2001). A Dictionary of Epidemiology, 4
th
edition

6. “Study”
Encompases
•Surveillance
•Observation
•Hypothesis testing
•Analytic research
•Experiments

7. “Distribution”
Refers to analysis by:
•PersonWho?
•PlaceWhere?
•Time When?

8. “Determinants”
Etiologic factors for disease: BEINGS
•Biological, Behavioral
•Environmental
•Immunologic
•Nutritional
•Genetic
•Services, Social, Spiritual

9. “Specified Population”
A group of individuals with
identifiable common characteristics:
•Place of residence
•Gender
•Age
•Occupation
•Religion

10. Epidemiology study (tools):
a.Defines the involved populations
b.Counts cases
c.Calculates and compares rates
(distribution)
d.Interprets findings
(determinants/outcomes)
e.Develops interventions – to control and
prevent disease in community (effects)

11. Demography
•the study of statistics such as births, deaths,
income, or the incidence of disease, which
illustrate the changing structure of human
populations.

12. Epidemiology and Biostatistics
Epidemiology
–The basic science and most fundamental
practice of
•Public health
•Preventive medicine
–Completely dependent on biostatistics
Biostatistics
– The application of
 
statistics
 to biology
–Quantitative foundation of epidemiology

13. Uses of Epidemiology
Currently epidemiology is seen as useful in:
•understanding what causes or sustains
disease in populations
•preventing and controlling disease in
populations
•guiding health and health care policy and
planning
•assisting in the management and care of
health and disease in individuals

14. Some terminologies
•Epidemic,
•Pandemic,
•Endemic

15. Epidemic, Pandemic, Endemic
•Epidemic – excessive occurrence of a
disease
•Pandemic – an epidemic on a worldwide
scale
•Endemic – a disease that is habitually
present in a geographical region

16. Classic epidemiology
Deals with:
disease etiology (cause) in communities and
community origins of health problems.
Risk factors that may be altered in a
population to prevent/delay disease/death.

17. Classic epidemiology, example
Population A has a higher intake of saturated fat
than population B. if the populations otherwise
are identical (demography, clinical,
psychosocial, etc.), will population A have
higher frequency of CHD than population B?
Assuming the answer is “yes”, will an
intervention approach with lowering of intake
of saturated fat in the population prevent/delay
the occurrence of CHD?

18. Clinical epidemiology
Connected to clinical decision-making
Deals with patients in healthcare setting to
improve:
•Diagnosis
•Treatment
•prognosis

19. Clinical epidemiology, an
example
Will a group of patients with similar clinical,
demographic and psychosocial
characteristics fare better, on average, if
they receive treatment A or B?

20. Epidemiology: 2 Basic
Fundamentals
•Disease does not occur at random (disease
is non-random)
•Disease has causal and preventive factors
that can be identified through systematic
investigation of different populations in
varying places and time
Hennekens,
1987

21. History of Epidemiology
•Epidemiology evolved slowly as theories of
disease causation were developed, refined
and tested by many different players
•Early development was slow for about 2000
yrs and then more rapid progress in the last
approx 150 years

22. Historical perspectives
•Has involved various players who sought to
understand illness, injury and death from an
observational angle
•They provided information on prevention and
control based on what they had observed
•The study of disease has advanced from a
supernatural viewpoint to scientific procedures

23. •From no approach for assessment to
systematic method
•From no clear understanding of the natural
causes of disease to a knowledge of possible
causes, modes of transmission, outcomes
•From no means of controlling to effective
and scientifically tested methods

24. Key players in history
•Hippocrates – rational point of view
•John Graunt – used systematic methods and
developed life tables
•Thomas Sydenham – used observational
methods
•William Farr – advanced on Graunts work

25. In the 19
th
century …
•John Snow
•Ignaz Semmelweis
•Louis Pasteur
•Robert Koch
•Florence Nightingale
These made important contributions and the
field has continued to expand rapidly

26. Hippocrates (460 – 377 BC)
•The first epidemiologist
•Father of medicine
•The physician who became known as the First
epidemiologist
•Used the terms – epidemic, endemic
•External environment and lifestyle as a cause of
disease
•“On Airs, Waters, Places and Epidemics”

27. •Wrote three books which attempted to explain
occurrence of diseases from a rational
viewpoint, as a development of the supernatural
perspectives advanced before him
•Observed that disease occurred in different
locations, eg malaria in swampy places (earlier
the explanation would have been that the
malaria had just happened due to higher powers)

28. His contribution…
•Epidemiologic Observation of how diseases
affected population

29. •Epidemiology of scurvy – James Lind
•Epidemiology of cow pox and small pox –
Benjamin Jetsy
•Epidemiology of childbed fever in lying in
hospital

30. John Graunt (1629 -1674)
•Founder of vital statistics
•Haberdasher (seller of
men’s accessories)
•1662 Observation on “Bills
of Mortality”
•Pioneer of “vital statistics”,
life tables, life expectancy
and demography
•Constructed the first known
life table

32. John Graunt’s Observations
•More males are born than females and more
males die than females (annually)
•Mortality rate for children was high (only
25% survived to 26 years)
•In 1662 only 3% survived to 66 years
•Seasonal variation in mortality: Fall was
“the most unhealthful season”

33. At sixteen years end 40
At twenty six 25
At thirty six 16
At fourty six 10
At fifty six 6
At sixty six 3
At seventy six 1
At eighty six 0
 From whence it follows, that of the said 100 conceived there remains alive at six years end 64.
John Graunt: Life Table of Deaths in
London

34. 18
th
Century
Development of experimental studies in
which rates of disease in treated and
untreated groups were compared.

35. James Lind (1716 – 1794)
•Developed hypotheses
from epidemiologic
observations regarding
etiology & treatment of
‘scurvy’ ( a defect in the
synthesis of collagen)
•1795 – limes required
for all British Navy
seamen (“Limeys”).

36. 1747 – Lind on Scurvy
12 patients with Scurvy on board a ship with same diet
were divided into groups of 2
2 were given 1gt cider/day
2 were given 25 drops of elixir vitriol
2 were given 2 T vinegar/day
2 were given sea water
2 were given 1 nutmeg/day
2 were given 2 oranges + 1 lemon per day
“The most sudden and visible good effects were percieved from
use of oranges and lemons, one of those who had taken
them, being fit for service ….. The other appointed nurse to
the sick”

37. James Lind
Lind knew nothing about :
-Vitamins
-The biology of scurvy
He made interventions based purely
on chance and observation data

38. Edward Jenner (1749 – 1823)
Observed that dairy-maids developed only mild
disease called Cowpox and did not get Smallpox
during a disease outbreak (1796)
Tested his hypothesis:
Removed Cowpox material from the hand of a
dairy-maid and inoculated it into an 8-year old
boy (volunteer). He exposed the child to Smallpox
6 weeks later and the boy did not get the disease

39. Edward Jenner
Knew nothing about:
– viruses
– the biology of Smallpox
He made interventions based purely
on chance and observation data

40. 19
th
Century
Modern epidemiology evolves which
stimulated interest in:
–Public Health
–Preventive Medicine

41. William Farr (1807 – 1883)
•British physician
•Compiler of Abstracts (40 years)
•Investigated the frequent cholera
outbreaks in London
•Classified disease (ICD)
•Invented SMR (Standardized
Mortality Ratio)

42. 1839-William Farr
Organized the first Vital Statistics and
assumed command of the Registrar General
Office (RGO)
»Births
»Deaths
»Marriages

43. William Farr
The RGO provided necessary statistical facts
to develop initiatives in response to Public
Health problems:
For example, in 1843:
London: median age death – 45 years
Liverpool: 50% of newborns died before 6 years
Farr believed in the MIASMA theory

44. Elevation of Districts
iEEn Feet
Number of Terraces
from Bottom
Deaths from Cholera in
10,000 Inhabitants
Calculated Series
Under 20 1 102 102/1 = 102
20-40 2 65 102/2 = 51
40-60 3 54 102/3 = 34
60-80 4 27 102/4 = 26
80-100 5 22 102/5 = 20
100-120 6 17 102/6 = 17
140-160 18 7 102/18 = 6
Elevation and Cholera Deaths
Humphreys, NA (Ed): Vital Statistics: A Memorial Volume of Selections from
Reports and Writings of William Farr. London, Sanitary Institute, 1885 p. 2545
Elevation of
District in feet
No. of
Terraces
From bottom
Deaths from
Cholera/10000
inhabitants
Calculated Series

45. John Snow (1813 – 1858)
•British physician
(anesthesiologist)
•Student of William Farr
•Convincing evidence
that Cholera was
associated with
contaminated drinking
water and not from ‘bad
air’

46. John Snow
•Studied cholera throughout his medical career
•Established sound epidemiologic methods from
his studies
•Observed and recorded important factors related
to the course of disease
•Initiated the modern epidemiologic thinking
•Demonstrated the value of ‘descriptive
epidemiology’(person, place & time)

47. Conducted two major cholera
studies
•A descriptive epidemiologic investigation
of cholera outbreak in the Soho district of
London in the broad street area
•An analytic epidemiologic investigation of
a cholera outbreak where he compared rates
of cholera between those who sourced
water from two different water supply
companys

48. The descriptive study
•In 1840’ an outbreak in Soho and Golden square
district
•500 fatal attacks in 10 days, would have been
more had residents not fled
•Snow described incubation time, length of time
from incubation to death, modes of transmission,
and the role of ‘leaving the area”
•Studied the water flow, sources of contamination

49. •Observed that people living around a brewery
and a workhouse within Soho were less affected
by the outbreaks. These two company's had
their own water source, different from the
public one supplying their neighbours
•Using a dot map he recorded locations of all
deaths, plotted graphs showing onset of new
cases, peak and when the deaths subsided

50. •He noted that nearly all deaths occurred not
far from the broad street water pump
•Examined transmission of the disease
between relatives

51. The analytic study
•Five years later came another outbreak.
•Snow noted that one of the water companys
had moved its intake point from a place that
was below the city of london to higher
grounds, effectively now drawing sewage
and pollution free water
•The other company still had its intake point
below the city

52. •The city was still supplied by both company but
residents were free to choose their supplier.
•Cholera deaths remained fairly common. Snow
noted that water drawn from below the city was
associated with more deaths
•He visited household and found that out 44 deaths,
38 were associated with households who got their
water from the company that drew water
downstream

53. John Snow
Found that:
•Southward and Vauxhall took water from a
very contaminated part of Thames
•The Lambert Company, however, took their
water from further upstream where water was
less polluted
Hypothesis:
Contaminated water is associated with Cholera

54. John Snow went from door to door and
counted the number of deaths from
cholera and related it to where they
got their water from

55. His contribution..
•Concluded that cholera is waterborne
•He laid ground work for both descriptive and
analytic epidemiology
•Identified modes of transmission and
incubation times
•In the analytic study he was able to compare
cases with a comparison group hence
establishing the cause-effect association

56. •Later on, the vibrio cholerae connection
was made

57. Deaths from cholera per 10, 000 houses by source of
water supply, London 1854
Water
supply
#
of Houses
Deaths Deaths/10,
000
houses
Southwark

+Vauxhall
40,046 1,263 315
Lambeth
Co.
26,107 98 38
Other
districts in
London
256,423 1,422 56

58. John Snow’s hypothesis was correct
He did not know about
Vibrio Cholerae.
He based his conclusions only on
observational data

59. Ignatz Semmelwiez (1818 –
1865)
•MD General Hospital, Vienna, Austria
•1841 – 46 Mortality from Puerperal fever
MDs and Med StudentsMidwives and Midwife
students
120/1000 births
After 7 months of
washing and soaking
hands in chlorinated
lime: 12/1000 births
39/1000 births

60. Lady with the Stats
“To understand God’s thoughts we
must study statistics, for these are
the measure of His purpose”
Florence Nightingale (1820-1910)
•Developed statistical charts and
diagrams for medical reform
•Worked with Dr William Farr
•First female member of the Statistical
Society

61. Pioneer in Epidemiology
•“Florence Nightingale is still relevant to
statistics today. She is often quoted with
regard to ‘healthcare auditing’and ‘quality
management’. She is regarded as pioneer of
epidemiological methods for her use of
public health statistics”.
Florence Nightingale Museum Trust, March 1998

62. Walter Reed (1851 – 1902)
1898 Spanish-American War (2/3
of deaths were due to yellow
fever)
“Clean hut/dirty hut”- one of the
first applications of
epidemiologic research methods
to virology

63. Jószef Goldberger (1874–1929)
Pellagra-
•Treated patients with diet
•Showed that Pellagra is not
infectious disease, but has
dietary origin
Did not know about niacin and
tryptophan
Based his conclusions and ultimate
treatment recommendation only
on observational data

64. Others
•Louis Pasteur (1822 – 1895)
•Robert Koch ( 1843 – 1910)

65. Epidemiologic accomplishments
in the 20
th
century
•1950 Doll & Hill published the first case-
control studies on smoking and lung cancer
(UK).
•1950s Wynder & Graham- smoking and lung
cancer (USA)
•1954 Salk polio vaccine tested
•1959 Mantel & Hanszel developed stratified
analysis for case-control studies

66. •1960 McMahon first textbook
of Epidemiology
•1964 US Surgeons General
criteria for evaluation of
causation (smoking and
health)
•1970s Micro-computer
technology
•1980s Epidemiology of AIDS
•1990s Molecular
Epidemiology
Last 20 years:
•Legionnaire’s disease
•Toxic shock syndrome
(tampon use)
•Reye’s syndrome
(aspirin involvement)
•AIDS

67. THEORIES OF DISEASE
CAUSATION
1.Cosmic Telluric Theory
2.Theory of Divine retribution
3.Misma theory
4.Germ theory
5.Theory of causation

68. Cosmic telluric theory
•Period of primitive man
•There was no distinction between magic,
religion and medicine
•Astrology-orientation of heavenly bodies
explained all events
•Evil forces produced disease and death
•No therapeutic or prevention programs

69. Theory of divine retribution
•Period of dark ages to mid 19
th
century
•Divine punishment as cause of disease
•(Gods are angry)
•Severity of illness depends on the gravity of sin
•Healing would not occur unless the sinner
confessed
•Torture became part of the therapeutic program

70.  “Rabbi,” his disciples asked him, “why was
this man born blind? Was it because of his
own sins or his parents’ sins?”
 
3
 
“It was not
because of his sins or his parents’
sins,”
 Jesus answered.
John 9: 2 - 3

71. Miasma theory
miasma 
(
ancient Greek: "pollution")
•a noxious form of "bad air"
•Late 19
th
century
•Miasma was considered to be a poisonous
vapor or mist filled with particles from
decomposed matter (miasmata) that caused
illnesses.
•It was identifiable by its foul smell.

72. Miasma theory
•Certain diseases are more common in
swampy regions
•Putrefaction of decaying material released a
miasma that caused disease
•A vehicle for environmental roles for
disease causation
•Gave birth to the hygienic movement

73. Germ theory
•Followed the invention of the microscope
•Came to explain the miniscule animals
observed by microscope
•Initially postulated that the miasma caused the
spontaneous generation of these animals
•Later germ theorists (e.g., Louis Pasteur)
postulated that infectious diseases were caused
by self-replicating organisms

74. Theory of causation
•Began around the end of the 19
th
century and the
beginning of 20
th
century
•Agent related causation
•Emerged from studies involving experiments
•Various models postulated
–Ecological model
–Holistic model
–Sufficient causation model

75. Over to you
Read article on history of epidemiology
•Hippocrates
•Disease observation of Sydenham
•The epidemiology of scurvy
•Epidemiology of cowpox and small pox

76. •Epidemiology of childbed fever
•Epidemiologic work by Koch and Pasteur
•John Grant and vital statistics
•Occupational health and industrial hygiene
•Florence Nightingale
•Typhoid mary
•Vitamins and nutritional epidemiology

77. •Epidemiology in the US
•The Framingham heart study
•Historical development of morbidity in
epidemiology
•Cigarette smoking and cancer

78. 15 topics among 60 of you.
Work in groups of 4
Write a summary of what you have read in
one page or less
Email to me by Thursday. (list names)
You all should read the whole doc