Epidemiology Flashcards
Descriptive epidemiology
-deals with describing the pattern of diseases
Analytical epidemiology
-attempts to make associations of observed patterns in order to make inferences in a hypothesis driven manner
Genetic epidemiology
-the epidemiological evaluation of the role of inherited causes of disease in families and in populations
Incidence
- number of newly diagnosed people in a specific time interval for a specified size of the population at risk
- measured against time
Cumulative incidence
- most common measurement of incidence
- valid in cohort studies where attritition is low
- due to attrition, incidence density (incidence rate) is aused
Incidence density
- aka incidence rate
- expresses the number of new cases per person-year of observation
- measured in time-1
Prevalence
-the number of existing cases in a specified population for a period of observation
Point prevalence
-cross sectional observation of prevalence (at any one time)
(No of existing (both new and old-dead and cured))/ cross sectional population of that area on that date
Period prevalence
- prevalence over a specified time frame
- number of existing (both new and old- dead and cured)/ mid year population at an area
Prevalence and incidence
incidence x duration of illness
Lifetime prevalence
- proportion of individuals in the population who have ever manifested a disorder who are alive on a given day
- has someone ever in their life had the illness- prone to recall bias
Lifetime morbid risk
- LMR
- probability of a person developing the disorder during their entire life period
- includes the entire lifetime of a birth cohort both past and future and includes those deceased at time of survey
Baseline prevalence
-usual prevalence of a disease in a community
Endemic
- if baseline is low to moderate and continues without significant fluctuation then the disease is endemic in the community
Hyperendemic
- a persistent but high level of the baseline
- most psychiatric disorders are low level endemic disorders
Epidemic
-occurrence within an area clearly exceeds the expected level in a given time period
Pandemic
-epidemic in wide geographical proportion
Crude rate
-rate applicable to whole population
Specific rate
-rate applicable to a subgroup of a population
Standardised rate
-a rate applicable to a hypothetical population with an adjusted variable e.g age
Crude mortality rate
-ratio between number of deaths due to all-cause in a population and total population size
Cause-specific mortality rate
- e.g alcohol specific mortality
- refers to the ration between number of deaths due to alcohol in a population and total population size
Case fatality rate
- ratio between number of deaths due to a specific disease and number of persons affected by the disease in a population
- measure of fatal severity of the disease
Proportionate mortality rate
- measure of the contribution of a disease to the societal mortality burden
- ratio between deaths due to specific cause and total number of deaths in a population
Years of potential life lost (YPLL)
- a measure of the impact of premature mortality on a population
- calculated as the sum of the differences between some predetermined end point and the ages of death for those who died before that end point
- most common end points are age 65 and the average life expectancy
- measure gives more weight to an earlier death than later deaths
Disability adjusted life years
-DALY
-one DALY represents the loss of one year of equivalent full health
DALY= YLL+ YLD
YLL= years of life lost due to premature mortality in the population
YLD= years lost due to disability for cases
YLL
-years of life lost due to premature mortality in the population
-YLL= Nx LE
N= number of deaths
LE= standard life expectancy
YLD
-years lost due to disability for cases
-YLD= Ix DWxLD
-I= number of incident cases
DW= weight given to the disability
LD= average duration of the case until remission or death (life until death in years)
Neonatal death
-a liveborn that dies within 28 days
Early neonatal death
-live born that dies within 7 days
Late neonatal death
-liveborn that dies between 7 and 28 days
Stillbirth
-foetus dies before birth but after 24 weeks of gestation
Perinatal death
-still births+ early neonatal births
Postneonatal deaths
-deaths from 1 month to one year
Infant deaths
-deaths under 1 year
Constrictive pyramid
-fewer people in the younger age categories e.g US
Expansive pyramid
- large number of people in a younger age categories
- typical of developing countries
Stationary pyramid
- roughly equal numbers of people in each category but tapering towards older categories
e. g Sweden
First generation epidemiological studies
- before world war 2
- 16 studies looking at prevalence of mental disorders in relation to community characteristics
Second generation epidemiological studies
-looked at diagnosis, classification and numenclature after world war 2
Third generation epidemiological studies
-started in 1970 with more effort into increasing the reliability of psychiatric diagnoses
Fourth generation studies
- current phase
- includes studies into biological markers, csf etc in large cross sectional surveys e.g H70 study
