MEASURES OF MORTALITY AND OTHER DISEASE IMPACT Flashcards
Morbidity
presence of disease in a population.
Mortality
The state of being susceptible to death
• Measure of the number of deaths in a particular population per unit of time
• Serves as a measure of “disease severity”; surrogates for incidence rates
Mortality Rate
MORTALITY RATES
- Annual death rate (mortality rate) from all causes
- Specific death rate (annual death rate w/restriction)
- Case-Fatality Rate
- Proportionate mortality (proportion,not a rate)
Annual death rate from all causes formula
Total no. of deaths from all causes in 1 year/ No. of persons in the population at mid-year (x1000)
Specific death rate(annual death rate w/restriction)
• Age-specific mortality rate
• Disease-specific mortality rate
• Cause-specific mortality rate
• Other demographics:gender, race, etc.
Case-Fatality rate
• Percentage of people who have a certain disease and who die within a certain time after disease diagnosis
• Use date of diagnosis as a surrogate measure for date of
disease onset
Case Fatality Rate Formula
no. of individuals dying during a specified period of time after disease onset or diagnosis/ no. of individuals with the specified disease (x100)
Numerator of Mortality Rate
Number of death from all causes or number or death from specific cause of death.
Numerator for Case Fatality Rate
- Restricted to deaths only from specific disease.
- Technically not a rate, but a percentage.
Denominator for Mortality Rate
Entire population at risk of dying from the disease.
Denominator for Case Fatality Rate
Limited to those who already have the disease of concern (Measure the severity of disease).
Proportionate mortality (proportion, not a rate)
• Describes the proportion of deaths in a specified population over a period of time, attributable to different causes
• Each cause is expressed as a percentage of all deaths
• Sum of the causes must add to 100%
Formula for Proportionate Mortality
no. of deaths/ total deaths(x100)
MORTALITY INDICES
- YPPL
- DALY
YPLL
Years of Potential Life Lost = 75 years;
• Measure of premature mortality, or early death
• U.S.A (and most developed nations) = 75 years of age
• Philippines (as of 2020) = 72.12 average years of life
DALY
Disability-Adjusted Life Year (DALY)
• Another index of disease burden
• 1DALY=1 lost year of healthy life
FORMULA FOR DALY
• Formula: years of life lost to premature deaths + years lived with a disability of specified severity and duration
Risk
Proportion of persons who are unaffected at the beginning of a study period, but who experiences a risk event DURING the study period
Cohort
Constitutes the people at risk for the event at the BEGINNING of the study period
Case fatality ratio
proportion of clinically ill persons who die
Pathogenicity of the organism
proportion of infected
persons who are clinically ill
Infectiousness of the organism
proportion of exposed persons who become infected
Force of mortality (FOM)
•Represents the instantaneous rate of mortality at a certain age measured on an annualized basis
•Force of mortality:greatest in A,lowest in B,intermediate in C
Rate
• Number of events that occur in a defined time period divided by the average number of people at risk (ideally: midyear) for the event during the period under study
• Often used to measure risk
Crude Death Rate
• Number of deaths occurring among the population of a given geographical area during a given year, among a population of 1,000 people
• “Crude” because all ages are represented
Instantaneous death rate /hazard rate
When death rate is expressed as describing reality at an instant in time (probability of death over a short period)
A rate is a good approximation of risk if the:
• Event in the numerator occurs only once per individual during the study interval
• Proportion of the population affected by the event is small (e.g.<5%)
• Time interval is relatively short
Incidence density
if event in the numerator occurs
more than once during the study
SPECIFIC TYPES OF RATES
- Incidence rate
- Prevalence rate
- Incidence density
