Epidemiology: Concepts & Indices
Terms
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- Epidemiology
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study of:
- the DISTRIBUTION of HEALTH STATES
- EVENTS in POPULATIONS
- the DETERMINANTS that influence those patterns - Leading cause of mortality
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Chronic diseases (because of aging population)
**NO longer infectious diseases - Descriptive Epidemiology
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- study of DISTRIBUTION of disease
- who, what, when, and where?
- discuss diseases in terms of person, place, time
(ex. what diseases? who are affected? where are they occurring?)
- Analytic Epidemiology
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- study of the origins & causes of disease
- how & why?
- deals with determinants of health
- Who was Hippocrates?
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- father of MEDICINE
- 1st person to use ideas related to epidemiology
- examined geography, climate, seasons, food & water consumed, habits & behaviours of people - John Snow
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- father of EPIDEMIOLOGY
- showed that water supply was related to development of cholera
- Florence Nightingale
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- worked in the Crimean War helping British soldiers
- looked at relationship between environmental conditions & recovery
- improved environmental conditions - 20th century shift
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- shift from looking at single factors to seeking combinations of factors that lead to disease
- shift in focus from infectious diseases --> to chronic diseases - Center of public planning
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EPIDEMIOLOGY because of:
- biological terrorism threats
- new infectious diseases
- recurrence of drug resistant strains (of older diseases) - How CHNs identify patterns of disease in a group?
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- surveillance
- monitoring - Morbidity
- occurrence of DISEASE or POOR HEALTH in the total population at risk
- Mortality
- number of deaths due to disease or health state or event in a population at risk
- Vital Statistics
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Vital events that are systemically registered with the state
(ex. births, deaths, and marriage) - Risk
- the PROBABILITY that an EVENT WILL OCCUR within a specified period
- High-risk population
- those persons for whom there exists a GREATER PROBABILITY of the event occurring
- Endemic
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rate of occurrence that is USUAL in a population (NORMAL or EXPECTED)
(ex. cholera or TB is endemic to developing countries) - Epidemic
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rate that EXCEEDS the usual level for that condition
(ex. incidence has INCREASED) - Point Endemic
- frequency of cases produces a SHARP PEAK, or point over a SHORT INTERVAL of time
- Pandemic
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worldwide outbreak of disease
(has nothing to do with how toxic a disease is, but how widespread it is) - Proportion
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ratio that shows the relationship between the TOAL NUMBER & FREQUENCY of OCCURRENCE
- often expressed as percentage - *Rate
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a measure of the FREQUENCY of a health event in a defined population during a SPECIFIED PERIOD
- how quickly something happens (per 1000 or 10,000)
- basic measure in epidemiology
(ex. incidence rate)
- Standardized rates
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- rates can be misleading when compared across different populations
- age adjustments (standardization) reduce bias
(ex. one population has much older population than another so would naturally have higher death rate) - Incidence Rate
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# of NEW cases developing in a population at risk during specified time
(# of new cases/population at risk of becoming new cases) - Prevalence Rate
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# of CURRENT cases (old and new)
(# of current cases/size of population) - Potential Years of Life Lost (PYLL)
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- measures premature mortality
- # of years of potential life lost by each death before age 65
- sums the individual PYLLs for all individuals who died that year - Dependency Ratio
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- describes the relation between the potentially self supporting portion of the population & the dependent portions (very young and older than 65)
(population < age 15 + population >or= 65/population ages 15-64) - Crude Birth Rate
- # of births per year (per 1000 people)
- General Fertility Rate
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average # of births to each women in her lifetime
(ex. 2.1 births per women) - Crude mortality rate
- # of deaths per year (per 1000 people)
- Age-specific mortality rate
- # of deaths in that age group/# of persons in that age group in the population
- Cause-specific mortality rate
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# of deaths from a specified cause during time period/total population at mid-point of time period x 100,000
- Case Fatality Rate
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PROPORTION of persons diagnosed with a particular disease who die within a specified period
(ex. if 15 of every 100 males diagnosed with prostate cancer dies within 5 years, the 5 year case fatality rate is 15%. The 5 year survival rate is 85%) - Maternal mortality rate
- # of maternal deaths related to child bearing/# of live births in that year x 1000
- Infant mortality rate
- # of infant deaths before age 1/# of live births in that year x 1000
- Neonatal mortality rate
- # of infant deaths before 28 DAYS of age/# of live births in that year x 1000
- Perinatal mortality rate
- # of stillbirths and deaths in the 1st week of life/# of live births in that year x 1000