Lecture 10- Descriptive Epidemiology

Question 1

What is descriptive epidemiology

Answer 1

Classifies the occurrence of disease according to following variables:

Person, place, time

Question 2

What are study designs in descriptive epidemiology

Answer 2

Case report, case series, cross-sectional

Question 3

Case report

Answer 3

In-depth study of one case, no comparison group

Question 4

Case series

Answer 4

Three or more cases involving patients that were given similar treatment, no comparison group

Question 5

Cross-sectional

Answer 5

Looks at data at a single point in time, participants are not selected based on outcome or exposure status, just based on inclusion/exclusion criteria

Question 6

What is an ecological study

Answer 6

Special type of cross-sectional study. Study in which the units of analysis are populations or groups of people rather than individuals

Question 7

What are some examples of ecological studies

Answer 7

Incidence of disease following vaccination programs

How tobacco taxes effect tobacco use

Certain occupations and hearing loss

Cancer rates and dietary practices by country

Question 8

What are the descriptive epidemiology measures

Answer 8

Count
Ratio: proportion, percentage, rate

Question 9

Count (descriptive epidemiology)

Answer 9

Refers to number of cases of a disease or other health phenomenon being studied

Question 10

Ratio (descriptive epidemiology)

Answer 10

Ratio is a relationship between two number

Question 11

Proportion (descriptive epidemiology)

Answer 11

Comparison of a part to a whole, type of ratio in which the numerator is part of the denominator

Ex: proportion of deaths among men, proportion of lung cancer due to smoking

Question 12

Percentage (descriptive epidemiology)

Answer 12

Proportion that has been multiplied by 100

Question 13

Rates (descriptive epidemiology)

Answer 13

Compares 2 numbers, measures the frequency where event occurs in a defined population over a specific period of time

Ex: rate of breast cancer/1000 women or number of births/year

Question 14

Population at risk (PAR)

Answer 14

The members of the overall population who are capable of developing disease or condition being studied, usually the denominator in rate calculation

Question 15

Crude rate

Answer 15

Summary rate asked on the actual number of events in a population over a given time period

Ex: prevalence, incidence, morbidity rate, mortality rate

Question 16

Specific rate

Answer 16

Based on particular subgroup of the population defined

Ex: race, age, sex, specific case

Better indicator of risk than crude rates especially for conditions specific to defined subsets of population

Question 17

Adjusted rate

Answer 17

Measures where statistical procedures have been applied to remove the effect of differences in population distributions. Allows comparisons between groups having different population distributions for certain variables

Question 18

Prevalence

Answer 18

Measure of the number of affected persons, number of persons with disease of interest, number of cases/number of people in population

Question 19

Incidence

Answer 19

Number of new cases of diseases during a specific end time period, number of new cases/number of persons in population

Question 20

What are factors that cause prevalence to icnrease

Answer 20

Increase in incidence, longer duration of the case, in-migration of cases, prolongation of life of patients without a cure

Question 21

What factors cause prevalence to decrease

Answer 21

Decrease in incidence, shorter duration of disease, influx of healthy people into the population, improved cure rate of disease

Question 22

Morbidity rate

Answer 22

Numerator is the total number of illness in a population over a specificed time, denominator is the average population at risk over the same time period

= number of illness due to the disease in the time period/average number in population during the time period

Can multiply by 10000 to get per 1000 rate of target population

Question 23

Mortality rate

Answer 23

Numerator is the total number of deaths in a population over a specified time period, denominator is the average population at risk over the same time period

= number of deaths due to disease in the time period/average number in population during the time period

Can multiply by 1000 to get per 1000 rate of target population

Question 24

What are limitations of crude rate

Answer 24

Sex, age, race

Question 25

Adjusted rates- direct method

Answer 25

Used when you know the age-specific rates of mortality or morbidity in all populations under the study

Question 26

Adjusted rates- indirect method

Answer 26

Only need to know the total number of deaths (or cases) and the age structure of the study population, preferable when there are small numbers in particular age groups

Question 27

Limitations of adjusted rates

Answer 27

Are artificially created so can lead to misinterpretation, based on assumptions, should only be compared to another rate that was computed in the same way