Lecture 2, part 5 Flashcards
Possible interpretations for incidence increasing but prevalence decreasing
Dz duration is reduced
Dz is becoming more fatal
Possible interpretations for incidence stable but prevalence increasing
Slow recovery
Fatality reduced
Immigration of cases from other area
Possible interpretations for incidence stable but prevalence declining
Recovery time reduced
Immigration of cases outward to another area
What do we need to know for all measures?
Number of ppl affected by the dz
Size of the pop from which the cases arise
Length of time that the pop is followed
Definition of incident cases
All individuals who change in status from one state of health to another (such as non-dz to dz) over a specific period of time
Definition of prevalent cases
All individuals living with the health outcome of interest within a specified timeframe, regardless of when that person was diagnosed or developed the health outcome
What type of measure is mortality rate?
Incidence
Numerator of mortality rate
Deaths d/t a specific cause (or all causes)
Denominator of mortality rate
Total pop (at risk, but everyone is at risk of death)
What type of measure is cause fatality rate?
Cumulative incidence
Numerator of case fatality rate
Deaths d/t a specific cause
Denominator of case fatality rate
Number of cases of that specific dz
Type of measure of attack rate
Cumulative incidence
Numerator of attack rate
Number of cases of a dz
Denominator of attack rate
Total pop at risk (or exposed) for a limited time period
Type of measure for birth defect rate
Prevalence
Numerator of birth defect rate
Number of defects at birth
Denominator of birth defect rate
All live births
Type of measure of survival rate
Cumulative incidence
Numerator of survival rate
Number of living cases
Denominator of survival rate
Total number of cases of that specific dz
Definition of years of potential life lost (YPLL)
Estimate of the avg yrs a person would have lived if they had not died prematurely (measure of premature mortality)
Aspects of YPLL
Measure of the overall health of an area
All-cause mortality or cause-specific mortality
Places additional emphasis on deaths of younger persons (mathematically weights the total deaths by applying values to death at each age)
Formula for YPLL
YPLL = (avg life expectancy) - (age at death)
How is YPLL calculated for a pop?
The YPLL for all individuals who died in that pop is summed
How to calculate the YPLL for age groups
Use the midpoint
How to use scale in period prevalence
If dz is common, present as percentage
If dz is rare, present as per 1,000, per 10,000, etc.
Risk (cumulative incidence definition)
The proportion of an at-risk pop that develops a specific health outcome within a specified amt of time
Rate (incidence rate) definition
The frequency of incident cases per unit of person-time at risk, measures how rapidly events are occurring
