Study designs

Question 1

Nutritional epidemiological studies:

Answer 1

made up of a risk fcator or exposure, the outcome or disease, the study is designed around a research question

Question 2

Things to consider for a study design

Answer 2

Need to consider
* Population
* Strength and limitations of design
* Ethical issues
* Cost and time

Question 3

How to represent a desired population

Answer 3

Once the reference population is identified, methods for selecting subjects should be developed
* Goal is to enroll a study group who will represent this identified population

Question 4

confounding

Answer 4

example is “High Processed Food Diet and Heart Disease
confoundings are age smoking excericse

Question 5

a test hypotheses

Answer 5

enabling testers to test a hypothesis is a further goal allows comparisons of subjects with different levels of independent variables. different methods that show comparison groups are shown the same way

Question 6

independant variable

Answer 6

Independent variable
* The variable that is changed in a scientific experiment – “the input” * Examples: exposure to nutrient, physical activity levels
MAY BE MANIPULATED BY EXPERIEMENTER

Question 7

dependent variable

Answer 7

The variable that will be measured in the scientific experiment – the “output”
* Often a disease e.g. occurrence of bowel cancer, CVD, hypertension, renal failure
CAN BE MEASURED

Question 8

evidence of causation

Answer 8

Identifying the cause of disease to prevent it or cure it is a primary goal of epidemiology.

Question 9

the six key criteria of causation

Answer 9

1. Strength of Study Design
2. Strength of Association
3. Consistency of Association
4. Temporal Relationship between Cause and Outcome
5. Dose Response Relationship
6. Biological Plausibility

Question 10

evaluate the intervention

Answer 10

relevent to the study with the goal of evaluating an intervention eg drug treatment , surgical procedure

Question 11

primary data collection methods

Answer 11

where the investigator is the first to collect the data
sources include medical eximnations and interviews

Question 12

secondary data collection

Answer 12

DATA IS COLLECTED BY OTHERS

Question 13

Types of primary studies

Answer 13

1.Descriptive studies : designs the occurance of an outcome
2. Analytic studies describes the association between exposure and outcome

Question 14

observational studies

Answer 14

cross sectional, case series, case-control studies, cohort studies
- identify participants
- observe and record characteristics
- look for associations

Question 15

experiemental studies

Answer 15

before and after studies, comparative trials, randomised trials
- identify participants
-place in common context
-intervene
- observe/evaluate effects of intervention
22

Question 16

ecological study

Answer 16

compares rates of exposures and diseases in different populations using aggregate data not individual data
may compare data on diet and disease across countries
important for differentiating between genetic and environmental issues.

Question 17

cross sectional studies

Answer 17

carried out in a single point in time, often used to assess prevelence of a situation, to describe a current situation
unlike ecological studies it is known those with the disease is due to exposure

Question 18

case control study

Answer 18

People with a disease (cases) are compared to similar people without a disease (controls) to determine if the cases are more likely to have particular exposures that the controls.
* A case-control study is always retrospective because it starts with an outcome then traces back to investigate exposures.

Question 19

cohort studies

Answer 19

Follow a group of individuals over time to assess the incidence of a disease (or some other outcome)
* Are used to describe the effect of exposure to one or more factors of interest (potential risk factors) on the incidence of the outcome
* Can be prospective or retrospective/historical

Question 20

What is a randomized control trial

Answer 20

randomised= ensures that treatment groups are similar, at the start of the trial

controlled=control group allows us to conclude that any improvement in outcome is due to the test treatment rather than some other factor
Comparison is usually between a new regimen/ intervention and an existing standard of care or placebo
* Provides most convincing evidence of relationship between exposure and effect

Question 21

Types of RCT
1. Parrell group :

2. Crossover trial

Answer 21

1.each patient is randomised to recieve only one of the two different strategies

each patient recives one stratgey first and then the other randomised
2.