DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09

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DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09 Understanding occupational health intervention studies Jani Ruotsalainen, MSc, BSc, etc.

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DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09 Understanding occupational health intervention studies Jani Ruotsalainen, MSc, BSc, etc. So who the f@#k is this guy?!?. NOT associate Prof Jos Verbeek, sorry about that Researcher at FIOH and member of COHF - PowerPoint PPT Presentation

Transcript of DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09

Page 1: DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09

DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09Understanding occupational health intervention studiesJani Ruotsalainen, MSc, BSc, etc.

Page 2: DPPH Seminar: Possibilities of various study designs, Lammi Sept. 28-29, 09

Understanding OH intervention studies / FIOH / Jani Ruotsalainen / 22.04.23 2

So who the f@#k is this guy?!?

• NOT associate Prof Jos Verbeek, sorry about that• Researcher at FIOH and member of COHF• Degrees from psychology and Ψ research methods• Published 4 Cochrane reviews in as many years• Currently working on 3 updates and a new protocol• Also in charge of the quality of COHF database of OH

intervention studies (1412 records, Sep 27th) available through: www.cohf.fi

This is why:• I know lots of stuff about intervention studies• my examples will come from occupational health

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Understanding OH intervention studies / FIOH / Jani Ruotsalainen / 22.04.23 3

Timetable for this evening

15:00 – 16:00 Lecture16:00 – 17:00 Group work17:00 – 17:45 Dinner17:45 – 18:45 Discussion19:00 – Sauna, refreshments

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Different kinds of medical research

• Incidence/prevalence• Aetiological• Prognostic• Diagnostic accuracy• Intervention

• Qualitative

• Each answers a different kind of question – Needs its own quality criteria

• Because of time constraints we concentrate on intervention research

domain of the Cochrane Collaboration

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Why do we need a separate database for OH intervention studies?

• OH intervention studies are hard to find– Occupational health covers a vast range of medical fields– No specific indexing like MeSH terms in Medline

• With an OH specialty database it is easier:– for researchers to conduct reviews and to find out what

has not yet been studied– for OH professionals to refer to current best evidence

• Classification helps in finding information:– about specific OH problems– a lot faster

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What is an acceptable occupational health intervention study? PICO(S)

1. Participants: workers or employed patients2. Intervention: purposely induced change3. Comparison: e.g. usual care (placebo in drug trials)4. Occupational health outcome(s)

• exposure• behaviour• occupational disease, symptoms or signs• work ability, disability, return to work• injuries• quality of OHS• public health in the workplace

5. Study design: preferably RCT to minimize risk of bias

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What is an (OH) intervention?

1. Any purposely induced change i.e. an active manipulation of the environment, disease or behaviour– Prima causa is either a researcher or– Some other instance (e.g. legislation) and a researcher is

there to measure the effects

2. With the aim to improve occupational health or safety– What is the aim in improving nurse hand hygiene?

What is NOT an intervention:• Correlation study (e.g. noise > hearing loss)• Other examples?

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Understanding OH intervention studies / FIOH / Jani Ruotsalainen / 22.04.23 8

COHF codes for OH intervention studies

Study designs (A1-A4)A1 Randomised Controlled Trial (RCT)A2 Controlled Before-After study (CBA)A3 Interrupted Time-Series (ITS)A4 Before-After study (BA)

OH outcomes (B1-B7)B1 Exposure (to e.g. chemicals, noise, stress)B2 Behaviour (e.g. wearing protective equipment)B3 Occ. disease and symptoms (e.g. eczema, asthma)B4 Disability, sickness absence, return to work B5 Injuries B6 Quality of OH services B7 Public health at the workplace

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Outcome measures

• Ideally validated questionnaires, tests, etc. (MBI, HADS)• Sometimes what authors report as their result is NOT

what they actually measured• E.g. better knowledge of safe work practices is NOT the

same as using safer work methods• E.g. in a review about the effectiveness of stress

interventions would you accept anxiety or depression measures as indicators of stress?

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What is high quality?

• Let's assume we have come up with 1) a nice intervention and 2) a bunch of valid outcome measures

• What is the best way to estimate the "truth" regarding the effectiveness of our intervention?

• In other words, what is a high quality intervention study?• What kind of evidence would you believe?

• Exercise:– In twos or threes make up your own hierarchy of study

designs starting from highest quality all the way to lowest quality

– You have 5 minutes

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Evidence hierarchy (one version)

SUNY Downstate Medical Center. Medical Research Library of Brooklyn. Evidence Based Medicine Course. A Guide to Research Methods: The Evidence Pyramid.

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Another version

1. Systematic literature review and meta-analysis of randomised controlled trials (RCT)

2. Narrative (unsystematic) review of RCTs3. Single well performed RCT4. Non-randomised, controlled trial5. Time-series study6. Uncontrolled before-after study7. Case study (N = 1)8. Expert opinion

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Exercise: study design

• Is a 4-hour stress management course effective in preventing stress in nurses compared to a booklet on stress management?

• Compare pros and cons of different designsDesign 1:

– Course: 100 nurses in Helsinki University Hospital in 2009– Book: 100 nurses in Turku Municipal Hospital in 2009

Design 2:– Kuopio University Hospital: 200 nurses randomly assigned

to course or book in 2008Design 3:

– Course: 100 nurses in Oulu in 2008– Book: 100 nurses in Tampere in 2004

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Randomised Controlled Trials

Randomisation reduces systematic error or bias

RandomisationI

C

Outcome +

Outcome −

Outcome +

Outcome −• At participant level or at dept./company/worksite level• Idea is that chance "evens out" confounding factors (age, BMI, etc.)• Any difference between random allocation and selection?• More experimental control ≠ better research, only more accurate!!!

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Controlled Before-After studies

• Prospective, controlled studies, quasi-experimental

I

C

Outcome +

Outcome −

Outcome +

Outcome −

Allocation done according to convenience e.g. by wards

Measured baseline similarity i.e. matching is NOT equal to randomisation

Same goes for adjusting for confounders in analysis

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Interrupted time-series

• At least three measurements before and after

O+

O−

O+

O−

Intervention

O+O+ O+

O− O− O−

O+

O−

Time

Inju

ry

coun

t

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Before-After Studies

• Before-after assessment of programme evaluations or quality of care studies

• Comparison with arbitrary or incomparable controls

O+

O−

O+

O−

programme

O+

O−vs. I²

O+

O−

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Thank you for your attention!