Epidemiology Flashcards
Triad of epidemiological questions?
How does pattern of disease vary over time?
How does place in which population lives affect disease pattern?
How do personal characteristics of people in a population affect disease pattern?
What does descriptive epidemiology do?
Describe pattern of disease
What does analytical epidemiology do?
Make associations of observed patterns to make inferences in hypothesis driven manner
What is genetic epidemiology?
Epidemiological evaluation of role of inherited causes of disease in families and populations
What did Morton define genetic epidemiology as?
Science which deals with etiology, distribution and control of disease in groups of relatives and with inherited causes of disease in populations
Define incidence
Number of new cases diagnosed in specified time interval for specified size of population at risk
What determines population size for incidence?
Mid-interval population
Give formula for incidence
Number of newly diagnosed cases/mid-2014 population at an area
What must new cases include for incidence calculation?
Newly diagnosed patients whether cured or dead
What is the advantage of cumulative incidence?
Valid in cohort studies where attrition is low
When is cumulative incidence not helpful?
High attrition rate - as dropouts are excluded from being counted as new cases
What is used if high attrition rate and need to calculate incidence?
Incidence rate
What is incidence rate?
Number of new cases per person-year of observation
What is the unit of incidence rate?
Time-1
When are incident rate ratios used?
When reporting results that compare two groups incidence rates
What is prevalence?
Number of existing cases in specified population for period of observation
What is point prevalence?
Prevalence in cross-sectional observation
What is period prevalence?
Prevalence in longitudinal observation
Which cases are counted in prevalence?
New cases
Diagnosed before observation but still suffering disease
What does prevalence not count re cases?
Previously diagnosed but now cured or dead
Calculation of point prevalence
Number of existing cases/cross sectional population at an area on 11/11/2018
Calculation of period prevalence
Number of existing cases/mid year population at an area
Which illnesses will have higher prevalence?
Chronic
What formula expresses relationship between incidence and prevalence?
Prevalence = incidence x duration of illness
What is lifetime prevalence?
Proportion of individuals in the population who have ever manifested a disease who are alive on a given day.
What is lifetime morbid risk?
Probability of a person developing the disorder during the entire period of their life (often a specified period)
What does lifetime morbid risk include?
Entire lifetime of a birth cohort both past and future
Includes those deceased at time of survey
What is used to calculate lifetime morbid risk for low incidence disorders?
Summation of age-specific incidence rates live approximate LMR
What is baseline prevalence?
Usual prevalence of a disease in a community
When is a disease said to be endemic?
If baseline is low to moderate and continues without significant fluctuation
What is hyperendemic occurrence?
A persistent but high baseline
What occurrence are most psychiatric disorders classed as?
Low-level endemic
What is sporadic occurrence?
Irregular pattern of significant fluctuations from baseline
What is epidemic?
Occurrence within an area clearly exceeds expected level in a given time period
What is a pandemic?
An epidemic in wide geographical proportion
What is a crude rate?
Any rate applicable to a while population
What is a specific rate?
Any rate applicable to a subgroup of a population
What is a standardised rate?
A rate applicable to a hypothetical population with an adjusted variable e.g. age
What is crude mortality rate?
Ratio between number of deaths du to all-cause in a population and total population sie
What is case fatality rate?
Ratio between number of deaths from specific disease and number of people affected by the disease in population.
What is case fatality rate a measure of?
Fatal severity of disease studied
What is proportionate mortality rate?
Ratio between deaths due to specific cause and total number of deaths in a population
What is proportionate mortality rate a measure of?
Contribution of a disease to societal mortality burden
What is years of potential life lost?
Sum of the differences between some predetermined end point and ages of death for those who died before that end point
What is years of potential life lost a measure of?
Impact of premature mortality on a population
Most commonly used end points in years of potential life lost?
65 years
Average life expectancy
What do years of potential life lost give more weight to?
Earlier deaths
What is disability-adjusted life years (DALY)?
Health gap measure that extends the concept of potential years of life lost due to premature death to include equivalent years of healthy life lost in states of disability
What does one DALY represent?
Loss of one year of equivalent full health
What can be used to calculate DALYs?
3% time discounting and non-uniform age weights that give less weight to years lived at young and older ages
Calculation for DALY
Years of life lost due to premature mortality in population (YLL) + years lost due to disability for cases (YLD)
Calculation for YLL?
Number of deaths x Standard life expectancy at age of death in years (LE)
Calculation for YLD
Number of incident cases x weight given to disability x average duration of case until remission or death (life until death in years)
Define neonatal death
Liveborn that dies within 28 days
Define early neonatal death
Liveborn that dies within 7 days
Define late neonatal death
Liveborn that dies between 7-28 days
Define stillbirth
Fetus that dies before birth but after 24 weeks
Define perinatal deaths
Still births + early neonatal births
Define postneonatal deaths
Deaths from 1 month to 1 year
Define infant deaths
Deaths under 1 year
What does a frequency polygon show?
Frequency distribution
How does one create frequency polygon?
Mark number of observations within an interval with single point placed at midpoint of interval and then connect these points
What can population pyramids be helpful for?
Insight into trends in population over time
Types of population pyramids
Constrictive
Expansive
Stationary
What is a constrictive pyramid?
Fewer people in younger age categories.
Which type of countries have a constrictive pyramid?
E.g. USA - baby boom populations shift to more conservative birth dats
What is an expansive pyramid?
Greater number of people in younger age categories
High birth rates
Low life expectancy
Which type of pyramid is seen in developing countries?
Expansive
What is an expansive pyramid?
Equal numbers of people in all categories, tapering towards old age categories
Low, constant birth rate
High QoL
How many psychiatric-epidemiological studies belong to first generation?
16
What defines first psychiatric-epidemiological generation?
Studies carried out before World War II
What did first generation psychiatric-epidemiological studies focus on?
Health care agency registered prevalence of mental disorders in relation to community characteristics
How many studies in the second generation of psychiatric-epidemiological studies?
60
What did second generation psychiatric-epidemiological studies focus on?
Diagnostic criteria
Classification
Nomenclature of psychiatric disorder
What type of studies were the second generation psychiatric-epidemiological studies?
Field surveys in unstructured clinical interviews
When did the third generation of psychiatric-epidemiological studies start?
1970
What was the major objective of third generation psychiatric-epidemiological studies?
Increase reliability of psychiatric diagnoses
Obtain precise estimates of prevalence and incidence of MH disorders
What does fourth generation of psychiatric-epidemiological studies include?
Comprehensive sets of biological markers such as brain imaging, CSF, bloods etc
Large scale cross-sectional surveys e.g. H70 study
