Study Designs

Question 1

“research”

Answer 1

a rigorous and systematic investigation of any phenomenon

Question 2

rigorous

Answer 2

refers to quality of research - using appropriate methods and analytical techniques

Question 3

systematic

Answer 3

refers to the practice of conducting a research in a logical and orderly, disciplined manner

Question 4

Types of Study designs (8)

Answer 4

• ecological/correlation
• cross-sectional survey
• cohort study
• case-control study
• RCT
• clinical trial
• animal study
• systematic review or meta-analysis

Question 5

Descriptive/Exploratory Designs

Answer 5

• collected to ID potential associations
• useful to make recommendations for future research
• collect baseline data
• useful in developing hypothesis

Question 6

Nutritional Epidemiology

Answer 6

the study of the effect of nutrition on disease

⇒ ecological, case control, cohert

Question 7

Ecological/Correlation

Answer 7

• observation of a group of people usually within 1 geographical region and loo at diet with some outcome
• or compare a factor of interest among different groups and the estimates of the intake of food/nutrients for those groups

Question 8

Correlation strengths

Answer 8

• used as an exploratory tool
• yielded considerable knowledge about dietary factors and chronic diseases
• used to generate hypothesis

Question 9

Hard to establish causality

Answer 9

• most chronic diseases are multifactoral
• chronic diseases have long latency periods/ when do they start
• hard to accurately estimate intake
• multiple confounding factors

Question 10

Cross sectional Surveys

Answer 10

• a snap shot of an entity

- association between an indicator of nutrition and a health characteristic measured at the same time

Question 11

strengths of Cross sectional surveys

Answer 11

• snap shot of entire region
• used to ID factors that may affect the level of risk factor
• generates hypothesis

Question 12

Case Studies

Answer 12

• collect info on one or a few individuals
• collect comprehensive information about a cluster of characteristics
• usually do not manipulate the environment
• findings are very specific to the group you selected

Question 13

Surveys

Answer 13

• used to collect information on a larger group of individuals
• can be researcher or self-administered
• cross sectional surveys collected info at one point in time
  longitudinal surveys look at the issue over time

Question 14

Analytical Designs

Answer 14

exploratory/epidemiological ⇒ case control studies, cohort studies (next)
Explanatory - test ⇒ clinical trials, animal studies

Question 15

Case Control Studies (retrospective)

Answer 15

• a group of subjects with the disease is compared with a group without the disease and their exposure history is compared
• collect retrospective info on diet and lifestyle

Question 16

Strengths of Case Control Studies

Answer 16

• very useful for less frequent diseases
• cost and time efficient
• investigate hypothesis of causal relationship
• used to explore aetiology - very useful for strong relationships

Question 17

Cohert Study (prospective)

Answer 17

• a population of people are identified; measure baseline and then look at disease occurrence overtime
• people are followed over time, having a common characteristic or factors of interest

Question 18

Examples of Cohert Studies

Answer 18

Framingham studies 
Nurses Health Study
EPIC
Kadoorie Study 
APrON

Question 19

Strengths of Cohert Studies

Answer 19

• evaluation of time-related associations
• baseline info helps decrease recall bias
• examine possible causal factors exposures

Question 20

Cohert Studies (retrospective)

Answer 20

• looks backwards in time
• the outcome has occurred
• go back and collect data - can only include what has previously been recorded
• collect what might have contributed to the outcome

Question 21

Criteria for Distinguishing Association from Causation

Answer 21

Temorality ⇒ cause precedes effect
strength of association ⇒ large risk
dose-response ⇒ greater exposure - higher frequency of effect
consistency ⇒ repeatedly observed by independent investigators
biological plausibility ⇒ causal interpretation should fit with current science

Question 22

Randomized Clinical Trial

Answer 22

• subjects randomly assigned to diets and the development of the disease/risk factor for a disease is measured

Question 23

Strengths of RCT

Answer 23

• powerful design for evaluation practice and medical/dietary treatments
• proves feasibility and safety of treatments, compare one or more treatments

Question 24

Limitations of RCT

Answer 24

• Compliance
• can’t blind dietary or lifestyle factors
• what is the interpretation of negative findings
• problems with long term intervention

Question 25

Steps in Clinical Trial

Answer 25

- hypothesis - study designs and duration - subject selection ⇒ inclusion/exclusion, recruitment, screening - diet - study procedures ⇒ sample size, randomization, monitoring, compliance - statistics

Question 26

animal studies

Answer 26

critical to understanding mechanisms of cause and effect relationship proof to rationalize human trial biological plausibility

Question 27

PEN - practical based evidence nutrition

Answer 27

- series of knowledge pathways, each focussing on a topic | - developed from key practice questions and evidence-based answers

Question 28

Systematic reviews

Answer 28

keep up with evidence, resolve uncertainty of contradictory results, helps demonstrate lack of evidence, future research? - subjects are papers, not people

Question 29

Steps in a systematic review (8)

Answer 29

- formulate a question - choose a database - search/limitations - eligibility criteria - quality assessment (risk of bias) - data extraction - directly as is - synthesis of data findings - sensitivity analysis - which quality results are included?

Question 30

Types of Bias in Systematic Reviews (6)

Answer 30

selection bias (what was their reason for entering, sampling bias) outcome reporting bias (some outcomes not reported) citation bias (using one papers references for other reviews) publication bias (published only positive results) language bias duplicate bias