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INTRO TO EPIDEMIOLOGY
CHAPTER NOTES
TABLE OF CONTENTS
Chapter 1 – Page 2-
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Chapter 1:
Epidemiology: the study of the distribution and determinants of health-related states or events
in specified populations, and the application of this study to control health problems
- Based on word epidemic
o Hippocrates 400 BCE
Public Health: organized community effort to prevent disease and promote health, one of the
efforts organized by society to protect, promote, and restore the people’s health
Health: the absence of disease
- A state of complete physical, mental, and social well-being, not merely the absence of
disease or infirmity
Epidemic: occurrences of disease in clear excess of normality
Pandemic: an epidemic that affects several countries or continents
Endemic: a disease that is consistently present in the environment
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Chapter 2:
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Chapter 3: Epidemiologic Measures
3.1 Measures of Disease Frequency
- Quantifies how often a disease or conditioners occurs within a given population
(measures of occurrence)
- Main measures: incidence proportion, incidence rate, prevalence
- Closed populations (cohorts): Gain no new members after established, lose members
bc of death and not at risk of becoming a case
- Open populations: add new members through birth and immigration/lose through
death and emigration
- Incidence Proportion: a longitudinal measure of disease occurrence in which the
numerator consists of the number of disease onsets that occurred during the period of
observation and the denominator consists of individuals at risk
- Only in cohorts
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑜𝑛𝑠𝑒𝑡𝑠
𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑐𝑒 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛 =
𝑛𝑜. 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣. 𝑎𝑡 𝑟𝑖𝑠𝑘 𝑎𝑡 𝑏𝑒𝑔𝑖𝑛𝑛𝑖𝑛𝑔 𝑜𝑓 𝑓𝑜𝑙𝑙𝑜𝑤 𝑢𝑝
- Interpretation: an incidence proportion is the average risk of developing condition for
period of observation
- Incidence rate: the number of disease onsets divided by the sum of person-time in the
population
𝑛𝑜. 𝑜𝑓 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑜𝑛𝑠𝑒𝑡
𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑐𝑒 𝑟𝑎𝑡𝑒 =
𝑠𝑢𝑚 𝑜𝑓 𝑝𝑒𝑟𝑠𝑜𝑛 − 𝑡𝑖𝑚𝑒 𝑎𝑡 𝑟𝑖𝑠𝑘
- Person-time unit: amount of time a person is observed during the study
- Incidence rates in open populations
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑖𝑠𝑒𝑎𝑠𝑒 𝑜𝑛𝑠𝑒𝑡𝑠
o 𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑐𝑒 𝑟𝑎𝑡𝑒 = 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑖𝑧𝑒 𝑥 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑜𝑏𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑜𝑛
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Prevalence: the proportion of individuals in a population that have a disease or
condition at a specific point in time
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 𝑤𝑖𝑡ℎ 𝑡ℎ𝑒 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛
𝑝𝑟𝑒𝑣𝑎𝑙𝑒𝑛𝑐𝑒 =
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 𝑐𝑜𝑛𝑠𝑖𝑑𝑒𝑟𝑒𝑑
𝑛𝑜 𝑡ℎ𝑎𝑡 𝑒𝑥𝑝𝑒𝑟𝑖𝑒𝑛𝑐𝑒𝑑 𝑡ℎ𝑒 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑑𝑢𝑟𝑖𝑛𝑔 𝑎𝑛 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
𝑝𝑒𝑟𝑖𝑜𝑑 𝑝𝑟𝑒𝑣𝑎𝑙𝑒𝑛𝑐𝑒 =
𝑡𝑜𝑡𝑎𝑙 𝑛𝑜. 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 𝑐𝑜𝑛𝑠𝑖𝑑𝑒𝑟𝑒𝑑 𝑑𝑢𝑟𝑖𝑛𝑔 𝑡ℎ𝑒 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
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Assignment
Due Date
When To Do
Read Chapter 11
Due Sunday
Saturday 11:50 p.m.
Chapter 11 Quiz
Due Sunday
Sunday 12:40 a.m.
Read Chapter 12
Due Sunday
Sunday 1:00 a.m.
Chapter 12 Quiz
Due Sunday
Sunday 1:45 a.m.
Read Chapter 3
Due Sunday
Saturday 10:45 p.m.
Chapter 3 Questions
Due Sunday
Saturday 11:30 p.m.
PS Week 1
Reading/Practice/HW
Due Sunday
Sunday 2:30 p.m.
PS Week 2
Reading/Practice/HW
Due Sunday
Sunday 6:30 p.m.