Lecture 5 Epidemiology and biostatistics.ppt

Lecture 5
Epidemiology and Biostatistics

After completion the lecture the students enable to:
1. Describe the concept of Biostatistics, prevalence
incidence, and health indicators.
2. Identify the four stages of a disease or health
condition.
3. Explain the host, agent, and environment model.
4. Distinguish between incidence and prevalence in
health and illness states.

Biostatistics:
Is the science of statically measuring
population health conditions.
- Biostatistics is the primary public health
measurement and analytic science underlying
community health practice.
- Biostatistics helps to describe the extent and
distribution of health, illness, and conditions in
the community.
- Biostatistics aids in the identification of
specific health problems and community
strengths. .

A few Statistics
Rate, ratio, incidence, and prevalence are common terms
used to help describe illness and disease among population
groups
.
A rate: A statistical measures expressing the
proportion of persons with a given health
problem among a population at risk.
Number of events
A rate is= --------------------X100,000
Population at risk
.
A ratio: A ratio: is often used to compare one at-
risk population with another
.

Mortality: Death rate
.
Morbidity: Illness rate
.
Mortality and morbidity statistics are collected
routinely and used as indicators of the frequency
of deaths and disease as they occur in time,
place, and persons.
.

Incidence and Prevalence Rates
Incidence: Refers to the rate at which a specific
disease develops in a population.
An incidence rate is the number of new cases of an
illness or injury that occurs in a specific time.
Number of persons developing a disease
Incidence rate=------------------------------------- X
100,000
Total number at risk per unit of time.

Prevalence: measures all of the existing cases at a
given point of time
.
Prevalence includes the incidence (new cases) plus all of
the existing cases.
The prevalence rate is influenced by how many people
become ill, and by the number of people who die or do not
recover.
Number of persons developing a disease
Prevalence rate= ---------------------------------
X100,000
Total number at risk per unit of time

SOURCES OF INFORMATION
Epidemiologic investigators may draw data
from any of three major sources:
(1)existing data,
(2)informal investigations,
(3) scientific studies.

1) Existing Data
A variety of information is available nationally, by
state, and by section, such as county, region, or
urbanized area.
a. Vital Statistics
Vital statistics refers to the information gathered from
ongoing registration of births, deaths, adoptions,
divorces, and marriages.
Sources for vital statistical information include state
Web sites on the Internet, local and state health
departments, city halls, and county halls of records

b. Census Data
Data from population censuses taken every 10
years in many countries are the main source of
population statistics..
Population statistics can be analyzed by age,
sex, race, ethnic background, type of
occupation, income gradient, marital status,
educational level, or other standards, such as
housing quality.

c. Reportable Diseases
Each state has developed laws or regulations
that require health organizations and
practitioners to report to their local health
authority cases of certain communicable and
infectious diseases that can be spread through
the community.
All states require that diseases subject to
international quarantine regulations
be reported immediately.

d. Disease Registries
Some areas or states have disease registries or
rosters for conditions with major public health
impact. Tuberculosis and rheumatic fever registries
were more common when these diseases occurred
more frequently..
e. Environmental Monitoring
State governments, through health departments or
other agencies, now monitor health hazards found in the
environment. Pesticides, industrial wastes, radioactive or
nuclear materials, chemical additives in foods, and
medicinal drugs have joined the list of pollutants

 Health Indictors
Definition:
Health indicators are standardized measures by
which to compare health status and health system
performance and characteristics among different
jurisdictions in country

 Categories of Health Indictors
Categories of health indictors
Mortality and burden of disease Ex: Access data on life expectancy,
child mortality, morbidity..
 Health services coverage Ex: Access data on skilled birth
attendance, antenatal care, TB detection/treatment...
 Health systems resources Ex: Access data on health workforce,
hospital beds and health expenditure.
 Risk Factors Ex: Access data on water and sanitation, nutrition,
tobacco use...
 Inequities Ex: Access data on inequities in health care and health
outcome.
 Demographic and socioeconomic statistics as:
Access data on total population, birth/death registration

CONCEPTS BASIC TO EPIDEMIOLOGY
The science of epidemiology draws on certain
basic concepts and principles to analyze and
understand patterns of occurrence among
aggregate health conditions.

1. The host is a susceptible human or animal who
harbors and nourishes a disease-causing agent.
2. Many physical, psychological, and lifestyle factors
influence the host’s susceptibility and response to an
agent.
3. Physical factors include age, sex, race, and genetic
influences on the host’s vulnerability or resistance.
4. Psychological factors, such as outlook and response
to stress, can strongly influence host susceptibility.
5. Lifestyle factors also play a major role. Diet,
exercise, sleep patterns, and healthy or unhealthy
habits
I. Host, Agent, and Environment Model

Causative agents is factors that are present (eg,
bacteria that cause tuberculosis, rocks on a mountain
road that contribute to an automobile crash) or factors
that are lacking
The environment refers to all the external factors
surrounding the host that might influence vulnerability or
resistance.
The physical environment includes factors such as
geography, climate, weather, safety of buildings, water and
food supply, and presence of animals
The psychosocial environment refers to social, cultural,
economic, and psychological

Risk
To determine the chances that a disease or
health problem will occur, epidemiologists are
concerned with risk or the probability that a
disease or other unfavorable health condition will
develop.

Reference
Andresen, E., & Bouldin, E. D. (Eds.). (2010).
Public health foundations: Concepts and
practices. John Wiley & Sons

Lecture 5 Epidemiology and biostatistics.ppt

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