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

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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

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THANKS FOR LISTENINGEmail your doubts to: sarizwan1986@outlook.com