Nutrition Epidemiology

The Objectives

– Make up an independant opinion, give advice – Analyse a situation– Set up studies– Analayse and interprete the results– Compare with other studies– Communicate results

Learning objectives– Skills required:

• Find literature• Critically appraise a scientific document• Present findings to pears• Set up a study, data input, analysis

– Kowledge required• Basics of epidemiology• Evidence based • Specific nutrition epidemiology• Some knowledge about what science is

Course structure– Self learning, problem based learning– Critical reading and presentation of papers– Search literature– Set up a study– Analyse the results– Basic epidemiology– Operational analysis

What is Evidence Based Health Care ?

Recent development: last ten years Central question was: what is the best treatment

for my patient? From the individual level to a population based

analysis : clinical epidemiology. Is what I am doing the best strategy? What

alternatives are there and how do they perform? Make an informed choice.

What is Evidence Based Health Care ? 2

"Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research." (Sackett et al, 1997)

conscientious: profesional values and ethics, explicit : effective communication and judicious: context for the decision

What is Evidence Based Health Care ? 3

The practice of evidence-based medicine is a process of lifelong, self-directed, problem-based learning in which caring for one's own

patients creates the need for clinically important information about diagnosis, prognosis, therapy and other clinical and health care issues, in which its practitioners:

What is Evidence Based Health Care ? 4

Convert these information needs into answerable questions Track down, with maximum efficiency, the best evidence

with which to answer them (making best use of the increasing variety of sources of primary and secondary evidence)

Critically appraise that evidence for its: validity (closeness to the truth), importance (size of effect), and

usefulness (clinical applicability) Integrate the appraisal with clinical expertise and apply the

results in clinical practice Evaluate their own performance.

Why is it important? Unanswered questions. Information explosion: doubling of information in

19 years, In 1900 10.000 journals, in 1990 100.000 journals Less than 1% of info is rigorous for EBM uses Practitioners need to be able to sort the “wheat

from the chaff”. EBM provides a toolkit Life long learning: continuous increase in info,

the development of new capacities, need to adapt Clinical effectiveness

Clinical effectiveness

"The extent to which specific clinical interventions, when deployed in the field for a particular patient or population, do what they are intended to do [outcomes] - i.e. maintain and improve health and secure the greatest health gain possible from the available resources.

Worthwhile benefit of an intervention, efficacy: clinical studies

Effect in practise: effectiveness : real life situations, operational analysis and effectiveness studies

The process of Evidence Base: 5 Steps

Convert information needs into answerable questions Track down, with maximum efficiency, the best evidence

with which to answer them (making best use of the increasing variety of sources of primary and secondary evidence)

Critically appraise that evidence for its: validity (closeness to the truth), importance (size of effect), and

usefulness (clinical applicability) Integrate the appraisal with clinical expertise and apply the

results in clinical practice Evaluate their own performance".

Identify the Question Who is affected? What is being done? How are the effects measured? Compared to What?

Look up information

Standard text books: old , not evidence based Scientific literature Use help tools

– Commercial data bases in libraries: abstract searches, articles

– Internet data bases: MEDLINE, – Internet search engines, Altavista, yahoo, google,

Mamma. Com

Types of evidence

Determining natural history/prognosis: Cohort studies

Determining test characteristics: Cross sectional studies

Determining the effect of interventions: Randomised controlled trials

Where to search?

Who is affected? "explode PREOPERATIVE CARE" Patientsundergoing either a surgical operation or anotherinvasive procedure

What is being done? "explode PATIENT EDUCATION" OR "patientinformation" OR "leaflet$" or "pamphlet$"

How are the effects measured? "explore STRESS, PSYCHOLOGICAL" OR"explode ANXIETY" OR "explode PATIENTSATISFACTION" OR "LENGTH OF STAY"

Compared with what? Not being given a leaflet, being given usual verbalinformation

Hierarchy of evidence

IStrong evidence from at least one systematic review of welldesigned RCTs

IIEvidence from at least one properly designed RCT ofappropriate size

IIIEvidence from well designed trials without randomization:single group pre-post, cohort, time series or matched casecontrolled studies

IVEvidence from well designed non-experimental studies frommore than one centre or research group

VOpinions from respected authorities, based on clinicalevidence, descriptive studies or reports from expertcommittees

VI Someone once told me

Evidence versus Decision

Evidence relates to the study type and quality Decision takes the local context into account.

– A is more effective but ten times more costly: for the same amount of money we can reach more people

– Can these interventions be organised in the local setting? Need to be flexible, because the setting can change. Justify your decisions: context based. Guard against rapid changes: effective monitoring and evaluation.

Evaluate your performance Were my questions answerable? Did I find good evidence quickly and efficiently? Did I appraise the evidence effectively? Did my integration of the appraisal with my own

expertise and the unique features of the situation lead to a rational, acceptable management strategy?

Critical appraisal of Primary research

Appraise papers for their validity (closeness to the truth and usefulness (applicability).

80% of what you want to know can be found in 20% of the literature.

Primary research: original studies Secondary research: compilation of primary research:

putting all evidence together, variability and context dependence of studies give varying results.

Types of Clinical Question

Therapy, i.e. how to select treatments that do more harm than good (e.g. is aspirin effective in the treatment of migraine?)

Prevention, i.e. how to screen and reduce the risk for disease Is regular weighing useful?

Diagnosis, i.e. how to select and interpret diagnostic tests (What is the best test to identify iron deficiency?)

Aetiology/causation/harm, i.e. what are the risk factors associated with a particular condition (e.g. is there a link between tomato consumption and decreased risk of cancer? Do dietary fibers protect against Gastro intestinal cancer? Does vitamin A supplement in children decrease mortality rates?)

Prognosis, i.e. how to anticipate the patient's likely course (e.g. what is the average survival time for a patient with congestive heart failure)

Issues to consider when appraising any study 1.Are the results of the study valid?

(VALIDITY)

2.What are the results? (RELIABILITY)

3.Will the results help locally? (APPLICABILITY)

1. Validity

Are the results of the study valid?

Are the conclusions justified by the description of the methodology and the findings?

Is the methodology sound, have the authors made reasonable assumptions, are there confounding factors they have failed to consider?

If they are using a sample, have they selected this to avoid bias?

2. Reliability

.What are the results? What are the findings of this article? Is the effect demonstrated large enough to be of

significance? How confident are we that the results fall within the

bounds of reasonable expectation and are not a mere fluke?

3. Applicability

Will the results help locally?

Are the problems I deal with sufficiently like those in the study to extrapolate the findings?

Can I generalise from this study to my work place?

Checklist VALIDITY Screening questions1. Did the trial address a clearly focused issue (in terms of

the population studied, the intervention given, and outcomes considered)?

2. Was the assignment of participants to the intervention(s) randomized? (Hint: was an appropriate randomization method used, such as sealed envelope)?

3. Were all of the participants who entered the trial properly accounted for at its conclusion? (Hint: look for the completion of follow up, whether participants were analysed in the groups to which they were randomized)

Checklist VALIDITY 2.

Detailed questions 4. Were participants, professionals and study personnel

‘blind’ to the intervention(s)?

5. Were the groups similar at the start of the trial? (Hint: think about other factors that might affect the outcome, such as age, sex, etc.)

6. Aside from the experimental intervention, were the groups treated equally? (e.g. were they reviewed at the same time intervals?)

Checklist RELIABILITY

7. How large was the treatment effect?

8. How precise was the estimate of the treatment effect? (Hint: look for confidence intervals)

Checklist APPLICABILITY

9. Can the results be applied to the local population?

10. Were all important outcomes considered?

11. Are the benefits worth the harms and costs?

The journal club

In the journal club recently published scientific papers in the field of nutrition are presented and critically discussed by all participants. The club is spread over a number of sessions so that all participants can present a paper on rotation

Objectives of the journal club :

Learn how to perform a search for scientific literature in databases of libraries and on the internet.

Learn to read a scientific paper and critically analyse it in terms of relevance, design, internal coherence and validity of conclusions.

By presenting a paper, participants will acquire skills in presenting a topic to an audience with respect to clarity, respect of time, coherence and synthetic valour.

The different topics presented and discussed also document the classes given and broaden the knowledge of

the students in the field of nutrition.

Organisation of the journal club Every week one two papers Recent literature use pdf (electronic versions)

– J of Nutrition

– Am J Clin Nutrition

– Eur J Clin Nutrition : pkolsteren ICFSN

– Br Med J Topics to chose a the beginning: question

How to make a presentation Prepare well Respect the timing!!!! Exercise with friends, comment each other Keep It Short and Simple (KISS) In average one overhead takes 1 to 2 minutes. An overhead should contain just key topics, tables and

graphs (pictures) avoid long texts. Use supports: Overheads, powerpoint, don’t overdo it! Don’t put too much on an overhead

NO Guidelines for reading research papers

Reading research papers is partly a matter of experience and skill, and partly learning the specific vocabulary of a field. If you approach it step by step, even an impossible-looking paper can be understood.

1. Scan. Scan the paper quickly, noting basics like headings, figures and the like. This takes just a few minutes. You're not trying to understand it yet, but just to get an overview.

2. Vocabulary. Go through the paper word by word and line by line, underlining or highlighting every word and phrase you don't understand. Don't worry if there are a lot of underlinings; you're still not trying to make sense of the article.

Now you have several things you might do with these vocabulary and concept questions, depending upon the kind of question each is. You can

• a. Look up simple words and phrases. Often the question is simply vocabulary--what's a lateral malleolus, or a christa, or the semilunar valve. A medical or biological dictionary is a good place to look for definitions. A textbook of physiology or anatomy may be a good source, because it give more complete explanations. Your ordinary shelf dictionary is not a good source, because the definitions may not be precise enough or may not reflect the way in which scientists use a word (for example "efficiency" has a common definition, but the physical definition is much more restricted.)

b. Get an understanding from the context in which it is used. Often words that are used to describe the procedures used in an experiment can be understood from the context, and may be very specific to the paper you are reading. Examples are the "lithium-free control group" in a rat experiment or the "carotene extraction procedure" in a biochemical experiment. Of course, you should be careful when deciding that you understand a word from its context, because it might not mean what you think.

c. Flag this phrase as belonging to one of the major concepts of the paper--it's bigger than a vocabulary question. For example, a paper about diet and cancer might refer to "risk reduction," which you would need to understand in context and in some depth.

3. Comprehension, section by section. Try to deal with all the words and phrases, although a few technical terms in the Methods section might remain. Now go back and read the whole paper, section by section, for comprehension.

In the Introduction, note how the context is set. What larger question is this a part of? The author should summarize and comment on previous research, and

you should distinguish between previous research and the actual current study. What is the

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