introduction of epidemiology 2008

7/29/2019 Introduction of Epidemiology 2008

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INTRODUCTION OF

EPIDEMIOLOGY

P. Lutfi Ghazali



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DEFINITION OF EPIDEMIOLOGY

“the study of how disease is distributed in populations

and of the factors that influence or determine this distribution”.

“the study of the distribution and determinants of health-relatedstates or events in specified populations and the application of this study to control of health problems”.

“the science of occurrence of diseases in human population”.

“the study of the distribution and determinant of diseases andinjuries in human populations



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Objectives of Epidemiology

to identify the etiology or the cause of a disease and risk

factors[1] to determine the extent of disease found in the

community. to study the natural history and prognosis of disease. to evaluate new preventive and therapeutic measures and

new modes of health care delivery. to provide the foundation for developing public policy and

regulatory decisions relating in environmental problems.

[1] is factors that increase a person’s risk for disease



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Measurement of Morbidity and Mortality

Rates are defined as follows :

Number of events in a specified period

------------------------------------------------------------------------------ x k

Population at risk of these events in a specified period



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Measurement of …

A ratio expresses the relationship betweentwo numbers in the form :

X

--- x k Y



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Measurement of …

A proportion is a specific type of ratio inwhich the numerator is include in thedenominator, and the resultant value isexpressed as a percentage :

X

-------- x k

X + Y


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Measurement of …

Incidence rates measure the probability thathealthy people will develop a disease during a

specified period of time or “the number of newcases of a disease in a population over a periodtime”

Number of new cases of a disease

------------------------------------------------- over a period of time

Population at risk



Measurement of …

Prevalence rate measures the number of people in a population who have thedisease at a given time.

Number of existing cases of a disease------------------------------------------------------ at a point of time

Total Population



Natural History of Disease

Precli ni cal Phase Clinical Phase

outcome

Biological onset Symptom Diagnosis Therapy

of disease

Detectable Lead Time

by screening



Stage of

Suspectibility

Stage of Pre-clinical

Disease

Stage of Clinical

Disease

Stage of Disability

Disease not yet developed

Presence of risk factors

No disease manifestation

Progression under clinical horizon (no detectable signs and

symptoms)

Recognizable signs and symptoms

Divided based on morphological alteration, functional limitation

or objective assesment .

Outcome of disease :

death disease controlled with disability

disease controlled without disability



PREVENTION

Definition

The goals of medicine are to promote health, to

preserve health, to restore health when it is impaired, and to minimize suffering, and distress.These goals are embodied in the word “prevention”, which is easiest to define in the

context of levels, customarily called primary,secondary and tertiary .



Primary Preventionthe protection of health by personal and community-wide effect .e.g. preserving good nutritional status, physicalfitness, emotional wellbeing, immunizing against

infectious diseases, and making environmentsafe. Aims : altering suspectibility and reducing exposure

Strategy : 1. General health promotions 2. Specific protective measures



Secondary Preventionthe measures available to individuals and populations for early detection and prompt and effective intervention to correct departures from good health

Aims : cure disease, slow the progression,prevent complication, cut off the chain of transmission

Strategy : 1. Early detection of disease (screening) 2. Prompt treatment of disease



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Tertiary Preventionthe measures available to reduce or eliminate long term impairments and disabilities, minimize suffering caused by existing departures from good health, and to promote the patient’s

adjusment to irremediable conditions

Aims : alleviation of disability and restoration of effective functioning

Strategy :1. Limitation of disability 2. Rehabilitation



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Natural History of Disease…

introduction of epidemiology 2008

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