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Human nutrition and physiology > Epidemiological studies and biomarkers > Flashcards

Epidemiological studies and biomarkers Flashcards

1
Q

What is epidemiology used for?

A

Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in defined populations.

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2
Q

What can observational studies be divided into?

A
  • Prospective/retrospective
  • Survey, case-kontroll. cohort
  • longitudinall/cross-section
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3
Q

What defines a cohort study?

A

A cohort study is a particular form of longitudinal study that samples a cohort (a group of people who share a defining characteristic, typically those who experienced a common event in a selected period, such as birth or graduation), performing a cross-section at intervals through time.

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4
Q

Which type of study can you see a general effect?

A

Observational

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5
Q

Which study can be used to get more causal connections?

A

Intervention/Experimental

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6
Q

What can experimental/intervention studies be divided into?

A

Parallell/ cross-over

longitudinal

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7
Q

Which sort of study is good for looking at risk factors?

A

Experimental

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8
Q

During a intervention/Randomized control trial, what are important factors to avoid bias (= systematic errors)

A

Controlled
Balanced (as many in different groups)
Randomized (critical part)
Blinding (single and double blinding)

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9
Q

What is internal validity and external validity?

A

Internal validity = if high – subjects will follow what they have been told to do – retention – datakvalitet – study will be able to answer the question

  • External validity – be able to translate the study into a broader population – You then need a very diverse group - but because of that can also end up failing what you want to measure …
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10
Q

How does a cross-over study work?

A

It is intrapersonal - every individual is measured in comparason to herself.
First one treatment then wash-out period to cleanse (expected to go back to regular diet) then the other treatment.

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11
Q

What are some negative aspects with cross-over?

RCT

A

Risk of carry-over effect. Can “spill” between the treatments
Only reversible effects can be studied
Takes a long time

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12
Q

Positive aspects of cross-over?

A

Because intrapersonal effects - don’t need to take as many parameters into consideration - need way less people !
Also because there are more check ups –> more compliance !

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13
Q

How is a paralell RCT performed?

Positive vs negative aspects

A

By dividing the participants in different groups with different people and then measure the effects.
+ no risk of carry-over between treatments
+ shorter time than cross-over
- Alot more people needed (because of interpersonal variations) –> more money

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14
Q

What is CONSORT?

A
  • Made to reduce problem following false rapporting of data from randomised trials
  • Standardised way to rapport data
    Need to write the protocol in beginning and register –
  • Have to adhere to the hypothesis
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15
Q

What groups can observational studies be divided into?

A

Descriptive and analytical

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16
Q

What are the different Descriptive observational studies?

A

Prevalens: nr of cases right now
Incidens: nr of cases per time period

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17
Q

How is analytical observational studies made?

A

Mapping reasons through associatonal studies
Use statistical analysed data
- what is causing the diseases – typical routes – causative agents etc.

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18
Q

What are prospective observational studies?

A

When the participants are choosen, or a randomized selection of the entire population, before the “endpoint” occur.
- Risk that the choice of participants can lead to bias!

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19
Q

What are retrospective observational studies?

A

A group is choosen after the endpoint.
(ex. focus on a rare disease)
Risk: memory can be sensitive for measuring errors as “recall bias”

20
Q

Epidemiological studies are often….?

A

Analytical

21
Q

Describe a Kohort study?

Observational

A
  • Use a group of individuals with “something in common” that has been followed over a period of time.
    frequency of endpoint between exposure and no-exposed is measured and compared as a relative risk.
22
Q

What are the calculation used in a Kohort study?

A

Relative risk = RR = Re/Ru
Re= Nr cases under that period of time/total nr people in the exposed group
Ru= Nr cases under that period of time/total amount of people in the un-exposed group
RR = 1 –> no differense in risk
RR > 1 –> higher risk of exposure
(1.9 = 90% higher risk)

23
Q

What does longitudinal studies mean?

A

A longitudinal study (or longitudinal survey, or panel study) is a research design that involves repeated observations of the same variables (e.g., people) over short or long periods of time (i.e., uses longitudinal data).

24
Q

Cohort studies are longitudinal and prospective. What are some negative aspects?

A

Long follow up–> expensive and results take time
Problem with
- choice of participants -ex. in a certain area
- people quite
- Assume people have same habits during the long time - but people may change work and therefore are exposed to other risk factors

25
Q

What kind of study is a case control study and what does it do?

A

Retrospective study
- Risk factors are estimated backwards in time

  1. Cases are identified (ex. cases of heart attack)
  2. Controls are taken out (people that hasn’t had heart attack but are similar in other ways)
  3. Comparason by exposure of riskfactors
26
Q

How are case control studies measured?

A

By association between exposure and disease

being measured as “odds ratio” (OR)

27
Q 
What does 
OR = 1
OR = 1.9
OR = 0.9 
mean?
A

1 = no connection

  1. 9 = 90% increased risk
  2. 9 = 10% decreased risk
28
Q

Positive and negative aspects with case control studies?

A 
\+ Cheap and easy
\+ good study for rare diseases
- Big risk bias in comparason between case and controls
- cases can affect riskfactor --> bias
- hard to select representative controls
29
Q

What is a cross-sectional study and when can it be used?

A

is a type of observational study that analyzes data from a population, or a representative subset, at a specific point in time
- Can only get correlation between those measurments
- But can’s say anything about what comes first – exposure or outcome
- Very cheap – can be used in first investigation –
can then move on with more complicated design
- Hypothesis generated design

30
Q

What are some general problems with observational studies?

A

Bias
- Bias leads to wrong interpretation of the results

Confounding

  • Collection of factors that affect the disease
  • When another riskfactor is correlated to the one you observe affect the disease seperately
31
Q

Give example of confounding

A

Coffee’s association with lung cancer

- coffee connected to smoking –> lung cancer

32
Q

What are the 6 criteria that can be used as epidemiologic evidence of a causal relationship between a presumed cause and an observed effect

A
  1. Statistical power
  2. Biological plausability
  3. Relevant control group
    4) Time of exposure
    5) Dose response
    6) Reproducability
33
Q

What is a meta-analysis?

A

Meta-analysis is a quantitative, formal, epidemiological study design used to systematically assess the results of previous research to derive conclusions about that body of research. Typically, but not necessarily, the study is based on randomized, controlled clinical trials.

34
Q

Positive aspects of meta-analysis?

A
  • Many studies are too small to descover a effect (too low statistical power) - but can be used when combined with several
    Get an overview so don’t have too read every paper
    Can indicate publicationbias
    more general reflection of the results
35
Q

What are the consequenses of the problems in estimation of food in nutritional epidemiological studies?

A
  • Lack of precision and accuracy
  • Bias as a cause of randomized errors (as memory etc)
  • Hard to esimate long time consumption
36
Q

What are biomarkers and what can they be used for?

A

A molecule that reflects the intake and can be analysed in biological samples

37
Q

Where can biomarker be sampled from?

A

urine, whole blood, plasma, serum, adipose tissue, saliva, hair

38
Q

Serum vs plasma?

A

Serum (coagulated) = plasma minus proteins which were captured in the coagulation.

Plasma have not been coagulated only centrifuged.

(Serum can be seen as a bit cleaner)

39
Q

What are the three types of biomarkers?

A

“Recovery biomarker” -
“Concentration biomarker” - huge diversity
“Prediction biomarker”
- strongly correlated – very clear relation o intake – not effected by bioavailability in same extent

40
Q

Biomarker of whole grain?

A

Alkylresorcinoler DHPPA, DHBA

Plasma, urin, adipose tissue, short-long

41
Q

Biomarker for protein?

A

Nitrogen
24-Urin
Short time

42
Q

What can biomarkers be used for?

A
  • Can be used as ranking tool - can rank into different groups depending on intake
  • Include difference in bioavailability and denaturing in cooking - reflects internal dose
  • Can be used to validate other methods - also in combination to other methods
43
Q

What are the criteria fpr the perfect biomarker?

A
  • Needs to be specific molecule
  • Stable thorughout cooking
  • Known ADME (absorption, distribution, metabolism, and excretion)
  • SMall inter-individual variation of ADME
  • Easy to analyse in biological tests
  • Plausibelt dose respond relationship
  • Nothing else should effect results
  • Stay stable in biological tests
  • Reflect intake at specific time period (can calculate the half life – to know if it is reflecting what you have yesterday or last months)
44
Q

What affect the biomarker concentration?

A
  • Absorption
  • Distribution (to tissues)
  • Elimination (metabolism, excretion)
45
Q

Top down vs bottom up?

A

Top down:
- whan to analyse certain food with already known biomarkers - can use that
Bottom up -
Approach to find new biomarkers of food and diets. Feed people a food and then look for new biomarkers

46
Q

What method is used to find biomarkers?

A

Metabolomics

Human nutrition and physiology (17 decks)

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