Mid term Flashcards
Descriptive studies are primarily ..
hypothesis formulating
Studies that fall under descriptive studies
- ecological or correlational studies
- case reports & case series
- cross sectional studies or surveys
Analytic studies are primarily…
hypothesis testing
Studies that fall under analytic are
- observational
- intervention
Types of observational studies
- case control
- cohort
Types of intervention
randomized clinical trials (RCTs)
Descriptive design strategies
- who, what , where, when
- describe characteristics
Descriptive studies definition
primarily useful for formulation of hypothesis to be subsequently tested in analytic studies
Analytic design studies
-why
- search for factors associated with or predictive of outcome
Analytic studies definition
among individuals with appropriate comparison group, with appropriate time sequence
observational studies exposures…
are self selected
case control initial selection…
on basis of exposure status
Interventional studies exposures…
are allocated by investigator
Mortality in 90s
- pneumonia
- tuberculosis
- diarrhea & enteritis
- heart disease
- chronic nephritis
- unintentional injury
- stroke
- disease of early infancy
- cancer
- diphtheria
Mortality today
- heart disease
- cancer
- accidents
- chronic lower respiratory disease
- stroke
- Alzheimers disease
- diabetes
- influenza & pneumonia
- kidney disease
- suicide
measure of disease frequency are
- prevalence
- incidence
The measure of disease frequency is the
number of different measures of frequency of morbidity & mortality but most fall into : incidence & prevalence
Incidence is
the DEVELOPMENT of a disease among those who are free of disease (at risk) over a given time period
Prevalence is
like a snapshot of the proportion of who EXIST with the disease at a point in time.
two primary measures of incidence
- cumulative incidence
- incidence rate
Cumulative incidence
the proportion of those who are disease free, who become diseased by the end of a specified period of observation
Cumulative incidence formula
CI = number of new cases developing in a specific time period / tot pop at risk
CI ( total pop at risk )
free of disease of interest & at risk of development
CI (specific time period )
- CI not interpretable unless time period is indicated
- everyone is followed for the same time period
Incidence rate
rate at which new cases of disease occur in a pop at risk for the disease
Incidence rate formula
IR = # of new cases developing over the study period / tot person time of observation
IR ( pop risk )
initially free of disease being studies
IR (new cases)
measure incidence of change in status from non case to case
IR (rate )
- time is intrinsic to measure
- true rate of development of disease
Prevalence formula
P = # of persons existing w disease / # of persons in tot pop
prevalence (tot pop)
denominator composed of diseased & non diseased
prevalence ( existing cases)
could be new cases, could be pre existing
prevalence cases
provides information about a populations current disease status
prevalence (point in time )
- time point must be indicated when reporting prevalence
- could be chronological; life event , life period
Prevalence keys
existing & proportion
Prevalence combined formula
P= I x (average duration)
- under steady state
