2. Measures of Disease Learning Objectives
Measures of Disease: Learning Objectives
1.Understand different types of populations as conceptualized in epidemiology and the relevance
of population types to measures of disease
2. Understand concept of disease occurrence in time
a.Understand and be able to define concepts of disease occurrence in time at a population level
(age, period, cohort effects)
b.Understand and be able to define concepts of disease occurrence in time at an individual level
(i.e., latent period, lead time), and their implications for measuring disease at the population level
3.Understand and be able to define and contrast prevalence and incidence
4. Understand and be able to define and contrast risks and rates
5. Calculate and interpret prevalence (this includes knowing the formula)
6.Understand, define, calculate, and interpret cumulative incidence (this includes knowing the
formulas)
a.Know different methods for calculating cumulative incidence and the assumptions and purposes
of each
7. Understand, define, calculate, and interpret incidence density (knowing the formulae)
a. Understand and calculate person-time
8.Define and interpret a hazard rate
9.Understand and be able to convert between prevalence, cumulative incidence and incidence
density (this includes knowing the formulas)
10. Direct and indirect standardization
` a. Perform both and understand when each is appropriate (know the formulae)
b. Know what data are required for each
3. Measures of disease outline
– Big picture
– Illustration/discussion of measuring disease in time
– Populations
– Time scales affecting disease in populations
– Epidemiologic measures
• Basic concepts
• Measuring diseases
• Prevalence
• Incidence density (incidence rate)
• Cumulative incidence (risk)
• Relations among measures
– Standardization
4. Big picture
• In epidemiology, one of our major goals is to
measure occurrence of disease
– Tool for surveillance (the “distribution” of disease;
descriptive epidemiology)
– Tool for etiologic/risk factor research (the
“determinants” of disease; analytical epidemiology)
5. Big picture
• Critical part of etiologic research
– We compare measurements of disease between
groups of people (e.g., exposed and unexposed)
because we are interested in associations between
exposures and outcomes and, ultimately, effects
(causal) of exposures on outcomes
6. Big picture
• Reminder: we compare disease occurrence
between groups of people that have different
exposures because we do not observe the
counterfactual outcomes for each person in the
population
– Comparisons of disease occurrence covered in next
module – measures of association
• Key step in etiologic research process is
accurate measurement of disease occurrence
