Epidemiology Terminology
Define epidemiology.
The study of the distribution and determinants of disease frequency in human populations.
True or false: Risk and incidence rate are the same metric.
False - risk refers to incidence proportion which uses population-level data and is divisible by the total population at-risk for disease, while incidence rate evaluates individual-level data and is divisible by the total person-time at-risk for disease
Define crude mortality rate.
The total number of deaths for all causes out of the total population in a specific time period.
True or false: causation and association mean the same thing.
False - association means that X and Y are related, while causation means that X leads to Y
Define prevalence.
The proportion of individuals with new and existing disease in a population in a specific time.
Define primary prevention.
A type of prevention that aims to prevent disease before it occurs.
What is the incidence proportion, or risk, of stroke over the course of this 5-year study?
7 new cases over 5-year study / 200 at-risk participants = 0.035 x 100 = 3.5%
There is a population of 100,000 people in a country in 2020. In this year, 250 people died: 100 from heart disease, 75 from cancer, and 75 from all other causes. In this population in 2020, there were 6,000 people who had heart disease and 3,500 people who had cancer.
What is the crude mortality rate in 2020?
250 total deaths / 100,000 total population = 0.0025 x 10,000 = 25 deaths per 10,000 (or 250 per 100,000)
Two examples of disease determinants.
Two of: demographics, lifestyle factors, psychological factors, genetics, epigenetics, pathogens, chemicals, environment, societal factors
Define incidence.
The proportion of individuals with newly developed disease in a population in a specific time.
Define case-fatality.
The proportion of people with a disease who will die from that disease.
How much person-time was contributed by each of the following groups:
*Participants who had a stroke?
*Participants who were lost to follow-up?
*Participants who did not have a stroke nor were lost to follow-up?
*Stroke cases = (2.5 + 1.5 + 3.5 + 4.5 + 0.5 + 3.5 +4.5) = 20.5 person-years
*LTF = (0.5 + 2.5 + 1.5) = 4.5 person-years
*Non-cases/non-LTF = (200 total participants - 10 with stroke or LTF) = 190 * 5-years of follow-up = 950 person-years
There is a population of 100,000 people in a country in 2020. In this year, 250 people died: 100 from heart disease, 75 from cancer, and 75 from all other causes. In this population in 2020, there were 6,000 people who had heart disease and 3,500 people who had cancer.
What is the case-fatality of cancer in this population in 2020?
75 deaths from cancer / 3,500 people with cancer = 0.02 x 100 = 2%
Difference between epidemiologic & clinical perspectives.
Epidemiologic perspective evaluates populations, disease determinants, and makes recommendations for public health.
Clinical perspective evaluates individuals, diagnosis of disease, and treats disease.
A study of 100 individuals was recruited in 2013. At the beginning of 2013, 40 of these individuals were identified as having high cholesterol. At the beginning of 2014, the researchers readministered cholesterol tests and found that 5 people had developed high cholesterol.
What is the prevalence of high cholesterol in this population in 2013?
40 existing cases / 100 total population = 0.40 = 40%
Define tertiary prevention.
Prevention that aims to reduce the impact of clinical disease.
If the risk of stroke in a 5-year study is 4%, what is the odds of stroke?
Odds = 0.04 / 1-0.04 = 0.04 / 0.96 or (when divided, ~0.04)
There is a population of 100,000 people in a country in 2020. In this year, 250 people died: 100 from heart disease, 75 from cancer, and 75 from all other causes. In this population in 2020, there were 6,000 people who had heart disease and 3,500 people who had cancer.
What is the cancer-specific mortality rate in 2020?
75 cancer deaths / 100,000 total population = 0.00075 x 10,000 = 7.5 cancer deaths per 10,000 (or 75 per 100,000)
What is the necessary cause in this sufficient-component cause model?
A
A study of 100 individuals was recruited in 2013. At the beginning of 2013, 40 of these individuals were identified as having high cholesterol. At the beginning of 2014, the researchers readministered cholesterol tests and found that 5 people had developed high cholesterol.
What is the incidence proportion of high cholesterol in this population in 2014?
5 new cases / (100 - 40 existing cases) =
5 / 60 = 0.0833 = 8.33%
Define proportionate mortality.
What is the incidence rate of stroke in this 5-year study?
Incidence rate = 7 new cases / 975 person-years or
7 per 975 person-years (or, 7.18 per 1000 person-years)
There is a population of 100,000 people in a country in 2020. In this year, 250 people died: 100 from heart disease, 75 from cancer, and 75 from all other causes. In this population in 2020, there were 6,000 people who had heart disease and 3,500 people who had cancer.
What is the proportionate mortality attributable to heart disease and cancer?
(100 deaths from heart disease + 75 deaths from cancer) / 250 deaths =
175 / 250 = 0.7 x 100 = 70%
Name five of Hill's Criterion for Causality.
Five of: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment, and analogy.
What belongs in each column of the blank table and how do we obtain each of those pieces of information?
Column 3: The total population in Community A (or, standard population) in 2015 - taken from original Community A table
Column 4: Age-standardized (or age-adjusted) mortality rates of Community B in 2015