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.