intro to epidemiology

Question 1

what is public health?

Answer 1

science & art of preventing disease, prolonging life & promoting health through the organised efforts of society

Question 2

what is the difference between medical health & public health?

Answer 2

clinicians treat people and diseases 1 at a time whereas in public health researchers, practitioners & educators prevent disease and injury at the community and population level

Question 3

how does public health contribute to:
(a) health protection?
(b) improving people’s health?
(c) health services?

Answer 3

(a) researchers, practitioners & educators prevent disease and injury at the community and population level

(b)action to improve health & well being. to reduce health inequalities

(c) ensuring our health services are most effective, efficient and accessible as they can be

Question 4

what is epidemiology?

Answer 4

science that underpins public health medicine & helps directs action

-study of the distribution of disease and the study of causes of disease and application of this study to control health problems

Question 5

how is epidemiology used? (what do you find out with it)

Answer 5

• study the natural history of diseases
• searching for causes & risk factors
• surveillance of disease (frequency, mortality rate, lead to disability?)
• investigate outbreaks, epidemics & pandemics
• study prognostic factors (clinical cause of condition - why some people have worse prognosis than others)
• studying effectiveness of diagnostic modalities
• planning & evaluation of health services
• developing health policies

Question 6

what is meant by exposure?

Answer 6

any factor that may be associated with an outcome of interest (e.g. risk factor or a therapy (medicine)

Question 7

what is meant by cases?

Answer 7

usually refers to patient

Question 8

what is meant by outcome of interest?

Answer 8

events that may occur as a result of the exposure or an intervention (e.g. development of a disease or resolution of a disease)

Question 9

what is prevalence of disease?

Answer 9

proportion of the population that has disease at a particular time (new & existing cases), usually expressed as %

Question 10

what is incidence of a disease?

Answer 10

new cases of disease in a population over a particular period of time. usually expressed as a rate

Question 11

what is relative rate?

Answer 11

incidence of disease in those who are exposed to a factor/incidence of diseases in non exposed to a factor (the ratio of the risks for an event for the exposure group to the risks for the non-exposure group)

Question 12

what is primary data?

Answer 12

data collected directly from first-hand experience, usually for the purpose of particular research project

e.g. interviews, surveys, questionnaires, field observations, case studies

Question 13

what is secondary data?

Answer 13

data that have already been collected for another purpose, often routine collected data

e.g. previous research, health records, government reports, official statistics

Question 14

what are a few examples of secondary health data?

Answer 14

• hospital discharges & outpatient data
• primary care data
• deaths
• births
• prescribing data
• performance data
• registries
• lab data
• surveillance of infectious diseases & organisms

Question 15

what are types of epidemiology studies?

Answer 15

observational & interventional

Question 16

what are the types of interventional epidemiology studies?

Answer 16

• randomised control trials
• controlled clinical trial
• community intervention study

Question 17

what are the types of observational epidemiology studies?

Answer 17

descriptive & analytical

Question 18

what are the types of descriptive observational epidemiology studies?

Answer 18

• case report
• case series
• cross sectional studies
• ecological studies

Question 19

what are the types of analytical observational epidemiology studies?

Answer 19

• cross sectional studies
• case control studies
• cohort study

Question 20

what is descriptive observational study?

Answer 20

examining the distribution of disease in a population, and observing the basic features of it’s distribution

Question 21

what type of questions are you looking at in descriptive observation?

Answer 21

look at what, who, when & where

= what problem?
= what magnitude?
= where and when did it happen?
= who is affected?

Question 22

what is analytic observational study?

Answer 22

investigation of a hypothesis about the cause of disease by studying how exposures relate to disease

Question 23

what type of questions are you asking in analytic observation studies?

Answer 23

= why/how? = causes, risk factors, modes of transmission

Question 24

what are ecological studies?

Answer 24

= type of descriptive observational study

-look at high level data at population level (rather than individual level) - looking for associations between an outcome & an exposure
e.g. levels of air pollution in different cities compared to n.o of hospital admissions with respiratory diseases

Question 25

what are strengths and weaknesses of ecological study?

Answer 25

strength = rapid & inexpensive, use existing data & generates hypotheses

weakness = not individual data - we don’t know if any of the individuals with the outcome were actually exposed to risk factor

Question 26

what is cross sectional observational study?

Answer 26

study where you assess prevalence of disease and/or risk factors at the same point in time
->snapshot of diseases & risk factors simultaneously in defined population

Question 27

what is the strength & weakness of cross sectional observational study?

Answer 27

strength = better for chronic diseases
weakness = which came first? prevalence of disease or risk factor? you can’t tell from this study

Question 28

what are cohort studies?

Answer 28

= type of analytical study
= group(s) of individuals are defined on the basis of presence or absence of the exposure to a suspected risk factor of a disease, then followed for a period of time to assess the occurrence of disease

• participants should be free from disease at start of exposure

Question 29

what are the 2 types of cohort studies?

Answer 29

1. prospective = looking now
2. retrospective/historical = looking back

Question 30

when are cohort studies problematic?

Answer 30

• outcomes being investigated are rare
• there’s a long time period between the exposure of interest & the development of the disease
• or it is expensive or very difficult to obtain exposure information from a cohort

Question 31

what are case control studies?

Answer 31

= compare 2 groups of people: those with the disease or condition under study (cases) and a very similar group or people who do not have the disease or condition (controls)

→involves 2 populations: cases & controls

Question 32

what are 3 distinct features of case control study?

Answer 32

• both exposure & outcome have occured before the start of the study
• the study proceeds from outcome /disease to cause
• it uses control or comparison group to support or refute (prove) an interference

Question 33

what are strengths & weaknesses of case control study?

Answer 33

strengths:
- quicker & less expensive (compared to cohort)
- smaller sample size required
- useful for rare diseases/outcomes
- can evaluate multiple exposures

weakness:

• can’t determine incidence or prevalence or causality
• not useful for rare exposure
• prone to recall & selection bias