Innføring til forskningsmetode - fra spørsmål til design

Presentasjon om: "Innføring til forskningsmetode - fra spørsmål til design"— Utskrift av presentasjonen:

1 Innføring til forskningsmetode - fra spørsmål til design

2 Spørsmål Design Vi trenger ulike typer studier for å besvare ulike spørsmål Spørsmålet bestemmer hvilket design eller forskningsopplegg som bør benyttes The aim of this session is to look at the main study types so that participants have some idea of the advantages and disadvantages of the different kinds of study and which might be appropriate to look at a question. We’ll be looking at some questions later but for now want to tell you about the studies you will come across.

3 Cross section studies En tverrsnittsstudie En tverrsnittsstudie (eller prevalensstudie) er en studie der informasjon er samlet på en planlagt måte i en definert populasjon (helst et represetativt utvalg) på et tidspunkt. You have just devised a cross-sectional study. Relevant to here and now. Confirm that it is a snapshot of a population. Preparation is very important. Refer back to preparing to answer question for leg ulcers. Intrepid 6

4 Fordeler og ulemper med tverrsnittsstudier
Cross section studies Fordeler og ulemper med tverrsnittsstudier Fordeler: Relativt billig og enkel å gjennomføre Ulemper: Kan ikke avdekke årsaksforhold Confounding This is a descriptive study and may give rise to a hypothesis. Often a very good way of just finding out what is actually out there. Intrepid 14

5 Kvalitative metoder Systematisk tilnærming for å beskrive eller forstå ett eller flere fenomener eller sammenhenger. Målet er ikke å kvantifisere, men å beskrive verden gjennom det opplevde og erfarte Hva er forskjellen på kvalitative studier og de andre studiedesign vi har snakket om? Målet er ikke å kvantifisere, men å beskrive (verden gjennom det opplevde og erfarte ) Kvalitativ metode er en systematisk tilnærming for å beskrive eller forstå ett eller flere fenomen eller sammenhenger. Metoden brukes stadig mer innenfor helseforskning og dere kan lese mer om den i boken *Medisinsk kunnskapshåndtering’ av Arild Bjørndal. (Studien er rettet mot den intervjuedes livsverden sikter mot å forstå meningen i denne livsverden får tak i og bruker informantenes egne kategorier er fleksible og holistiske foregår i en mellommenneskelig interaksjon ) Eksempler på forskningsmetoder er Observasjon Intervju Fordypningsgrupper Dokumentanalyse Spørreskjemaer

6 Kohort studie Ekponert Utfall Utfall Uekponert Populasjon
This shows how a cohort study works. Cohort comes from the Latin word for one of the ten divisions of an acient Roman legion. And the cohort study is looked upon as the next most powerful study design after the RCT The essential element of a classical cohort or follow-up study is that you follow two (or more) groups forward in time, counting the events or outcome that occurs in each. A cohort study compares people exposed to a suspected cause and those not exposed. Some ex of classical, closed cohorts are: (also called inception cohort) National Birth Cohort everyone born in a week in March 1958 Whitehall – civil servants, Overhead Whitehall Nurses Health Study – American female nurses are followed every 2 year with questionnaires – 1998 n published articles – associations between lifestyles, estrogen therapy, oral contraceptives and ca/coronary health etc..Overhead nurces Utfall Uekponert

7 Kohort study Studiepopulasjonene er definert på bakgrunn av ekposisjonen Utfall sammenlignes i gruppene med og uten eksposisjon eller risikofaktor Vanligvis er prospektivt forløp You can also find cohort studies that are historical. A historical cohorts excist when the subjects are identified on the basis of records of previous exposure – eks association between birthweight and CHD – the day the researcher decide to find out about this question she will go to a birth registers to find the birthweight on a defind group or cohort that is assembled a long time ago when exposure have been previousley documented The studies which explored the assos between asbestos and the development of mesothelioma (se Brocklehurst s 1) Overhead appendctomy Swedish girls which had had appendictemoy between 1964 and followed to no asscos between perforeted appendix and further fertility - surprisingly they could not find any association between perforated appendix and further fertility problems Open or dynamic cohort – eks Rover occupational cohorts often include people who leave and enter the workplace – difficult to follow the people who leaves and you often include new workers Same in health administrative cohort studies occupational cohorts or health administrative system cohorts can be open (Rover).

8 Kohort study Fordeler Ulemper kan følge forandringer over tid
kan måle sykdoms-incidens kan undersøke effekten av sjeldne eksposisjoner kan se på mer enn et utfall kan avdekke sammenhenger og time sequence Ulemper lang tid for å se resultater, dyrt vanskelig å oppnå 100% follow up bias og confounding Few investigators are willing to spend 10 or more years following up people. Even if the investigator was willing if might be difficult to assemble a large number of people who would be willing to participate in a long term study, and even if the people were willing, - the costs of the research would be extremely high. In this sircumstances cohort research is very difficult to conduct, because too many people have to be assembled for too long time. So a cohort study is difficult to conduct and it is also a challenge to appraise these studies and interpret their findings - but often cohort studies is the best evidence we find and we therefor need appraising skills The aim of cohort study must be to minimise bias and confounding and to try to find an assoc that is as close to the true ass as possible. To aschieve this it is important that a cohort study is well designed and well carried out.

9 Kasus-kontroll studier
Tid Forskning Utsatt Ikke Utsatt Ikke Usatt Kasus (personer med sykdom) Her er et diagram som viser det samme….. Populasjonen definert på bakgrunn av personer som har et utfall/sykdom (cases) og de uten utfallet/sykdommen (kontroller). Graden av eksposisjon eller risikofaktorer blir målt i de to gruppene som sammenliknes bakover i tiden. Kontroller (personer uten sykdom)

10 Kasus-kontrol studie Studiepopulasjonene er definert på bakgrunn av utfallet/sykdommen Graden av eksposisjon eller risikofaktorer blir målt i de to gruppene som sammenlignes Retrospektivt forløp You can also find cohort studies that are historical. A historical cohorts excist when the subjects are identified on the basis of records of previous exposure – eks association between birthweight and CHD – the day the researcher decide to find out about this question she will go to a birth registers to find the birthweight on a defind group or cohort that is assembled a long time ago when exposure have been previousley documented The studies which explored the assos between asbestos and the development of mesothelioma (se Brocklehurst s 1) Overhead appendctomy Swedish girls which had had appendictemoy between 1964 and followed to no asscos between perforeted appendix and further fertility - surprisingly they could not find any association between perforated appendix and further fertility problems Open or dynamic cohort – eks Rover occupational cohorts often include people who leave and enter the workplace – difficult to follow the people who leaves and you often include new workers Same in health administrative cohort studies occupational cohorts or health administrative system cohorts can be open (Rover).

11 Kasus-kontrol studie Fordeler Ulemper billig og rask
kan undersøke sjeldne sykdommer med lange latensperioder kan undersøke flere eksposisjoner Ulemper Kan ikke bevise en årsak/virkning Kan ikke undersøke sjeldne eksposisjoner Hva kom først; eksposisjonen eller sykdommen? Kan vanligvis ikke måle forskomst (insidens) Bias og confounding The biggest problems for case-control studies are finding accurate data on previous exposure Case-control studies are not difficult to conduct but are difficult to appraise and interpret. The aim of case-control study is to minimise bias and confounding and to try to find an association between cases and several exposures.

12 Kohort studie Ekponert Utfall Populasjon sykdom
This shows how a cohort study works. Cohort comes from the Latin word for one of the ten divisions of an acient Roman legion. And the cohort study is looked upon as the next most powerful study design after the RCT The essential element of a classical cohort or follow-up study is that you follow two (or more) groups forward in time, counting the events or outcome that occurs in each. A cohort study compares people exposed to a suspected cause and those not exposed. Some ex of classical, closed cohorts are: (also called inception cohort) National Birth Cohort everyone born in a week in March 1958 Whitehall – civil servants, Overhead Whitehall Nurses Health Study – American female nurses are followed every 2 year with questionnaires – 1998 n published articles – associations between lifestyles, estrogen therapy, oral contraceptives and ca/coronary health etc..Overhead nurces

13 Årsak eller sammenheng
Mange faktorer kan vise seg å ha en sammenheng med hverandre, men det behøver ikke bety at det ene er årsak til det andre We often use the word association in observational studies to indicate a relationhip. An association mean that the exposure and outcome variables changes together. Causation is a stronger word and observational studies seldom can identify a causal relationship It is not strictly possible to show causation in case-control studies are you are looking backwards in time. In order to show causation one needs to first see the exposure and then the development of a case. However, sometimes the weight of evidence from case-control studies becoming so great at you can accept their findings e.g. The association between lung cancer and smoking.

14 Kriterier for årsaksforhold
Tidssekvens (høna før egget) Dose-respons (mer eksposisjon = forøket risiko) Biologisk mulig Støtte av annen doumentasjon (Austin Bradford Hill, 1971) There are some “rules” of evidence that can be applaied to evidence of causation - they are put together from different methodologists, but mostly from . Dr Here are four of them and the ones you most often find

15 Tverrsnittsstudie Tverrsnittstudie med en representativt utvalg, hvor en test sammenlignes med en ”gullstandard”

16 Randomisert kontrollert forsøk (RCT)
utfall nytt tiltak gruppe 1 populasjon gruppe 2 utfall kontroll

17 Effekt av behandling eller fore-
Kunnskap om … Studiedesign Kjerne-spørsmål Diagnostikk Tversnittsstudie (med en gull- standard) Hvordan kan vi avgjøre.. Prognose Kohortstudie Hvordan går det.. Årsaker (etiologi)    Kohortstudie Kasus-kontrollstudie Hvorfor får noen… Effekt av behandling eller fore- bygging 1.   RRandomisert kontrollert studie 2. Kontrollert studie Hva kan vi gjøre.. Erfaringer Kvalitativ studie Hvordan oppleves det?