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II MBBS, Epidemiology series 1
Research Methodology‘Descriptive epidemiology’
Dr. Rizwan S A, M.D.,Assistant Professor,
Department of Community Medicine,VMCH&RI, Madurai.
27.10.2014
II MBBS, Epidemiology series 2
Outline
• Classification of research methods• Descriptive epidemiology– Basic premise – Procedures
1. Define the population2. Define and describe the disease3. Measure the disease4. Compare5. Formulate hypothesis
– Uses of descriptive epidemiology
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Classification of research methods
Research methods
Observational
Descriptive
Case series, case reports,
CS, cohort
Analytical
Ecological Cross-sectional
Cohort Case control
Experimental
Controlled Uncontrolled
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DESCRIPTIVE EPIDEMIOLOGY
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Basic premise
• First phase of an epidemiological investigation – When is the disease occurring? – time distribution– Where is it occurring? - place distribution – Who is getting the disease? - person distribution
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Procedures
1. Define the population2. Define and describe the disease3. Measure the disease4. Compare5. Formulate hypothesis
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1. Define the population
• ‘Population base’• Age, sex, occupation, cultural characters • ‘Defined population’ – denominator• Large enough
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2. Define and describe the disease• Definition – ‘operational definition’
• Time distribution– Short term; epidemics– Long term– Periodic; seasonal, cyclic
• Place distribution– International– National– Rural/urban– Local– Migration studies
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Place distribution – spot maps
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2. Define and describe the disease
• Person distribution– Age– Sex– Ethnicity, Race– Marital status– Occupation– Social status– Behaviour– Stress– Migration
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3. Measure the disease
• Mortality – rates• Morbidity - prevalence, incidence• Disability
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4. Compare with know indices
• By make comparisons between different populations, and subgroups of the same population, it is possible to arrive at clues to disease etiology
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5. Formulate hypothesis
• An epidemiological hypothesis should specify– the population – specific cause being considered – the disease – dose-response relationship – time-response relationship
• Bad example– ‘Cigarette smoking causes lung cancer’
• Good example– ‘Smoking of 30-40 cigarettes/day causes lung cancer in 10 per
cent of smokers after 20 years of exposure’
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Uses of descriptive epidemiology
• Magnitude of disease– Mortality, morbidity
• Clues to disease aetiology• Background data for organizing and evaluating• Contribute to research
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Summary