Assessing the occurrence of disease: morbidtiy and mortality Flashcards
Global Burden of Disease
Study that was used to predict the future burden of disease.
Study examined mortality data and impact of premature death and disability on a population
Disability adjusted life year
Index that combined factors in global burden disease
What is a cohort?
A group of people who share the same experience
Differences in mortality over time or between populations may be:
Artificial or real
Artificial
numerator: errors in diagnosis, errors in age, changes in coding rules, changes in classification
denominator: errors in counting population, errors in classifying by demographic, errors in characteristics (age,sex, race) and differences in % of population at risk
Real
change in survivorship w/out change in incidence
change in incidence
change in age composition of the population
a combination of the above factors
Standardized mortality ratio (SMR)
resultant ratio from indirect age adjustment calculation
= observed no. of deaths per year/ expected no. of deaths per year
Mortality increases with old age
What are the two approaches used to account for age differences in two populations
Direct age adjustment
Indirect age adjustment
Direct age adjustment
a hypothetical standard population is created. This is then used to reduce the effects of any age differences between two or more populations being compared.
Indirect age adjustment
The no. of expected deaths in each age group in the population of interest is calculated and added together. The no. of deaths that were actually observed in the same population are likewise added together.
Problems with mortality data
most of the info comes from death certificates. On death certificates, deaths are coded according to underlying cause of death. Unfortunately the underlying cause of death does not contain info on the immediate cause of death or contributing causes of death
Why consider mortality?
It is an index of severity and risk of a disease. Is only a good measure of risk or incidence of disease when: case fatality is high and duration of disease is short
Morbidity: disease is mild and not fatal good incidence of disease
Years of potential life lost
measure of premature mortality or death reference age= 85 85-20=65 85-80=5 95-50=35 total=105YPLL
What are the two steps used to calculate years of potential life lost
1: for each cause, each deceased persons age at death is subtracted from the predetermined age of death ( generally 65 years)
2: The YPLL for each individual are then added together to yield the total YPLL for a specific disease
Proportionate mortality
ratio: no. of deaths from a specific cause per 100 or 1000 deaths from all causes in the same period
Gives indication of major cause of death
Formula for proportionate mortality
no. of deaths from certain disease/ total deaths overall
Case fatality rate
measure severity of disease
date of diagnosis used as surrogate for date of disease onset
Formula for case fatality rate
no. of people who die during a period after disease diagnosis or onset/ no. of people with the specific disease x1000