Epidemiology

Epi means above, upon
demos means people
logy means knowledge
Definition:
     The study of distribution and determinants (risk factors) of health related states or events in a specified population and the application of this study is to control health problems is called as Epidemiology.
It involves:
a) Distribution of Disease
b) Disease Frequency
c) Determinants of Risk factors
Types of Epidemiology
Descriptive epidemiology:
     The study of distribution of diseases in the society is called as descriptive epidemiology.
Analytical Epidemiology:
The study of determinants of risk factors of disease is called as analytical epidemiology.
Explanation

Disease Frequency:

     Epidemiology is the measurement of frequencies of diseases such as disability and deaths and summarize this information in the form of rates and ratios e.g. Prevalence (number of existing cases) rate, Incidence (number of new cases) rate, Death rate, Morbidity (disease) rate etc.

Rate and Ratio is the basic measurements of epidemiology in the frequency of the diseases. These rates are essential for comparing disease frequencies in different population or sub groups of the same population.

Distribution of Diseases:
     An important function of the epidemiology is to study these distribution patterns in various subgroups of the population by time, place, person etc. i.e. epidemiologist examine whether there has been an increase or decrease of disease over time spin. Whether there is a high concentration of disease in one geographic area than in other. Whether the disease occur more often in age related factors such as male, female or children etc. Such type of study is called as descriptive study.
Determinants of Disease:
     A unique feature of epidemiology is to test etiological factors and identifying the underlying cause. This require the epidemiological  principles and methods. Such type of study is called analytical study. Such study helps in the causation of the underlying risk factors and develop preventive measures and preventive programs for the promoting of good health.
Difference between Epidemiological and Clinical medicine:

• Epidemiology is the unit study in a defined population whereas clinical medicine is a case study.
• In epidemiology, the epidemiologist is concerned with the disease in the entire population whereas in clinical medicine individual patient is treated.
• Epidemiologist deals with the sick people as well as healthy people whereas in clinical medicine the doctor deals with the sick people.
• Epidemiologist goes to population and examine the patients whereas in clinical medicine the patient comes to doctor for examination.

Finally it is concluded that epidemiology and clinical medicine are not antagonizing each other but both are closed related and co relevant with each other. Without epidemiologiist , doctor do nothing and vice versa.
Approach of epidemiology:
Asking question and comparison.
Asking question:
Some of the question are as follows.
What is the event?
What is its magnitude?
What did it happen?
When did it happen?
Who are affected?
Why did it happen?
Measurement in epidemiology
     The scope of measurement in epidemiology is very broad and give us specific values for the specific measurements. These measurements are the following.

• Measurement of Mortality (death rate)
• Measurement of Morbidity (disease cases)
• Measurement of Disability 
• Measurement of specific infant Mortality
• Measurement of presence, absence or distribution of the characteristics attribute of the disease
• Measurement of medical needs, health care facilities, utilization of health services and other related events

Tools of measurement

• Rate 
• Ratio
• Proportion

      Rate is the number of particular events in a population during a given period of time e.g. crude rate, specific rate, standard rate. Ratio is the comparison b/w the two or division of one quantity by another quantity e.g. the sex of children attending an immunization clinic male and female).
                                                                  n
      Ratio, proportion, rate =  x     × 10
                                                y                                                                                                                                                                                               n
Rate =  number of  cases or events occurring during a given timeperiod   ×10      
              population at risk during the same time period

Aims of epidemiology
     According to the international epidemiological association, epidemiologyhas the three main aims.

• To describe the destribution and magnitude of health and disease problems in human population.
• To identify the risk factors in pathogenesis of disease.
• To provide the data essential for planning, implementation and evaluation  of services for the prevention, control and treatment of disease.

     These are the general applications of epidemiology. According to WHO, the ultimate aims of epidemiology are:

• To eliminate or reduce the health problems and its consequences.
• To promote, protect and restore the health.

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WHO (World Health Organization) 1948

Objectives:

ü  To strengthen the health services

ü  To promote standards of education, training and health related professions

ü  To provide information, assistance and counsel in health fields

ü  To promote nutrition, housing sanitation, and other aspects of environmental health

ü  To promote and conduct research

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Social sciences in community medicine

The social sciences in community medicine discuss the following predisposing factors which affect health by different ways.

        i.            Current circumstances:

Income, family life, family crises, employment etc

     ii.            Individual predisposing factors:

Accidents, chronic diseases (polio incidence), chronic disability, inheritance incidences, childhood nutrition

   iii.            Ecological predisposing factors:

The environmental factors including the community values, life styles etc

   iv.            Opportunities and situation:

a.       Availability of health services

b.      Pathogen avoidness

c.       Education status

d.      Drugs availability

The factors which affect the predisposing factors of current circumstances and individual predisposing factors are given below.

Ø  Political status:

Ø  Demographic factors

Ø  Economic factors

Ø  Religious factors

Ø  Education status etc

The factors which affect the ecological predisposing factors and opportunities are given as following.

ü  Communication

ü  Migration

ü  Urbanization

ü  Life expectancy

ü  Fertility (marriage partner)

Role of women (dominating role)

Social sciences:

The branches of sciences that studies society and the relationship of individual within the society are called social sciences.

v Economics:

Economics is a social science that analyzes the production, distribution and consumption of goods and services.

The word economics is derived from Greek Oikonomia (means laws or customs for household administration)

Economics explain how economics work and how economical agents interact. Economics analysis can be applied throughout the society such as in the family, in health, politics, religion, business, finance, crime and education.

It plays a key role in health.

v Anthropology:

Anthrop means man and logy means knowledge or study

The study of social, physical and cultural history of man is called anthropology.

It is concerned with human in any society with all dimension of humanity.

Types of anthropology

        i.            Physical anthropology:

The study of human evolution, growth, inheritance and human decay is called physical anthropology. It is sometimes also called as biological anthropology.

     ii.            Social anthropology:

The study of development of various types of social life is called social anthropology.

   iii.            Cultural anthropology:

The study of total way of life including ways of thinking, feeling and action in the human culture is called cultural anthropology.

    iv.            Medical anthropology:

The study of cultural components in the way of etiology of health and disease is called medical anthropology.

      v.            Linguistic anthropology:

The study of variation in languages across time and space is called linguistic anthropology.

v Political science:

The system of laws and institutions which constitute the government of the society is called political science.

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Incidence and Prevalence

Incidence:

Definition:

The number of new cases emerging in a specific period and area

OR

The number of new cases occurring in a defined population during specific period of time

Incidence= Number of new cases of specific diseases (during a given time period     × 1000

                     Population at risk during the same interval

Incidence demonstrates about:

·         New cases of the diseases during a specified period of time in a specified population and area

·         Incidence is not influenced by the duration of the disease

·         The of incidence is restricted to only acute diseases

Cumulative incidence:

CI = Number of disease people           × 100

        Total number of healthy people

Attack rate:

A.R. = number of disease people   × 100

            Number of exposed people

Prevalence:

The number of existing cases occurring in a defined population during a specific period of time

The term disease prevalence refers to all the existing cases in a specified area and in a specified time.

Prevalence = Total number of individuals having attribute or disease at a particular time

                        The population at risk of having the attribute or disease in a particular time

Types of prevalence:

         i.            Point prevalence: specific to days, month, age or sex

       ii.            Period prevalence: specific to period of time such as from July 2010 to July 2011

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Health & Rural health

WHO definition:

Health is state of complete physical, mental and social well being and not merely the absence of disease or infinity.

Webster (epidemiologist) definition:

The condition of being sound in the body, mind or spirit especially freedom from physical disease or pain is called health.

Oxford definition:

Soundness of body or mind to that condition in which its functions is accurately performed is called health.

In recent years the WHO definition has been amplified to include the ability to live a socially and economic productive life.

Rural health:

Rural area:

The area where the health facilities are very uncommon and is located at distance from urban areas is called rural area. Rural areas are deficient of various types of health facilities and also associated with many types of health problems.

Rural health problems:

·         Lack of specialist (concern doctor)

·         Lack of education

·         Lack of proper health care units

Ø  Primary health care units: BHO’s and Dispensaries

Ø  Secondary health care units: DHQ’s (District Head Quarter) hospital, THQ’s hospital

Ø  Tertiary health care units: Teaching hospitals (KTH)

·         Low economic and social status

·         Lack of transport facilities for workers of public health in rural area

·         Unemployment

·         Absence of control on communicable diseases

·         Physical environment (pollution by insecticides, pesticides etc)

Health of the Nation:

The health of the nation can be achieved by the following three ways.

         i.            Management

       ii.            Disease

      iii.            Drugs

Management:

Hospitals:

The hospitals play a key role in health of the nation. It provides the first aid in the form of medicine, vaccine and surgery etc.

BHU’s:

The basic health unit is under the supervision of district health quarters. They are monitored by doctor and nurses etc.

Dispensary:

This is also under the control of district health unit providing all the necessary facilities to the public.

Disease:

The diseases whose treatments are funded by the government are the following.

Ø  TB

Ø  Polio

Ø  Small pox

Diabetes mellitus and HIV are now given preference in Pakistan.

Drugs:

Those medicines which are harmful for the health of the people are condemned to use e.g. Morphine and cocaine etc.

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Demography & GOARN

Definition:

The scientific study of human population is called demography.

Demography is concerned with the following human phenomenon:

ü  Changes in population (growth or decline)

ü  Composition of the population

ü  Distribution of the population

It deals with the five demographic processes namely:

Ø  Fertility

Ø  Mortality

Ø  Marriage

Ø  Migration

Ø  Social Mobility

These above five processes are continuously are at work with in a population determining population size, composition of the population and distribution of population.

Demographic cycle:

We have the following five demographic stages or cycles.

a)    1^st stage (high stationary):

This stage is characterized by high birth rate and high death rate which cancels each other and the population remains stationary.

b)    2^nd stage (early expanding):

The death rate begins to decline while birth rate remains unchanged. It is due to health promotion. Many countries in South Asia and Africa are in this stage. Birth rate increased due to improve conditions.

c)     3^rd stage (late expanding):

The death rate declines still further and the birth rate tends to fall. The population continues to grow because birth exceeds death. China and Singapore are experiences this stage.

d)    4^th stage (low stationary):

The stage is characterized by a low birth rate and low death rate with the result that the population becomes low stationary.

e)    5^th stage (decline):

The stage is characterized by a low birth rate and high death rate with result of decrease or decline in population. This stage is found in Germany and Hungry.

Objectives of demography:

Some of the important objectives of demography are as follows.

         i.            The average size of the family would be reduced from 4-2 up to 3-2 children.

       ii.            The birth rate per thousand populations should be reduced to 21-50.

      iii.            The death rate per thousand populations would be reduced to 20-10.

     iv.            The infant mortality rate would be reduced to 60 or less.

       v.            The effective couple protection rate would be raised to at least 60%.

GOARN:

It stands for Global Outbreak Alert & Response Network. This network constantly alerts the community to the threat of outbreaks and ready to respond.

Objectives:

         i.            Combating the international spread of outbreaks

       ii.            Ensuring the appropriate technical assistance reaches affected states rapidly

      iii.            Contributing to long term epidemic preparedness and capacity building

The initial meeting of GOARN was held in Geneva in April 2000.

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