MODELS OF REHABILITATION RESEARCH

John Whyte, MD, PhDMoss Rehabilitation Research Institute

&Thomas Jefferson University

The ICF & Related Models Body structure (disease) Body function (impairment) Activity (disability) Participation (handicap)

Biomedical Research Deals primarily with body structure &

function Assumes that functional ability is directly

related to resolution of body structure/ function abnormalities

What about….. Improvement in function w/o improvement in

pathology? Improvement in pathology w/o improvement

in function?

SustainedAttention

WorkingMemory

LanguageComprehen-

sionBalance

MotorCoordination

DiffuseAxonalInjury

ContusionSensori-neural

Hearing Loss

DiabeticNeuropathy

DrivingPublic

Speaking

ParentingEmploymentB

ody

Stru

ctu r

eB

ody

Func

tion

Act

ivit

yPa

rtic

ipat

ion

Levels of Intervention

LEVEL OF OUTCOME

Body Structure

Body Function

Activity Participation

Body Structure Body Function Activity

LE

VE

L O

F

TR

EA

TM

EN

T

Participation

Implications for Research Ideally, research should clarify the

causal links among levels in the enablement/disablement process

Most NIH-funded rehabilitation research to date stays primarily at one level (and mostly at body structure/function levels)

Distinction between enablement/ disablement research and rehabilitation research

2 Case Examples The effects of oral antispasticity

medications (Whyte & Robinson, 1990)

The effects of cognitive remediation (Carney, et al, 1999; Cicerone, et al, 2000)

Implications for Training Investigators will need to work in

interdisciplinary teams Having in-depth knowledge regarding a

level above or below the “target” level can be ideal

Researchers need to build quantitative and testable models of these interrelationships

Who mentors the linkages?

Using Theory In Rehabilitation Research Is there an overarching theoretical

framework for rehabilitation? What focused theories are useful

for focused domains? How can these theories be applied

specifically to treatment research?

Key Elements in Efficacy Study Design

Defining the appropriate study sample

Defining the “active ingredients” of treatment

Defining the study outcomes Determining the overall study design

What do we mean by “treatment theory”? A proposed specification of the

“active ingredients” of treatment A proposed specification of the

mechanism of action of those active ingredients

Why do we need a treatment theory? Many rehabilitation treatment

interventions are multifaceted and interactive – what elements or processes make a difference?

Candidate active ingredients are infinite; we need to constrain them for study

Results of theoretically-driven treatment studies not only provide an empirical result; they support theory development and refinement

Multifaceted Treatments May consist of a set of tasks and

activities delivered by specific disciplines in a particular dose or schedule and according to a particular protocol

Which of these are important determinants of treatment outcome?

Reducing the Infinite Given multifactorial treatments, how do

we select which aspects to “manualize” in defining the treatment of interest? The color of the walls? The gender of the therapist?

Theory, rightly or wrongly, points to the indispensable, defining aspects of the treatment

We always have at least covert theories

Theory Development An empirical comparison of 2 treatments

simply establishes that one is better than the other; it provides no guidance how the better treatment could be improved upon, or what components of it could be sacrificed without losing potency.

A theory-based comparison eliminates a whole family of unsuccessful treatments and provides a dimension along which the better treatment can be tuned (e.g., reaching training in motor-lesioned monkeys)

Treatment Theory Can Inform Other Aspects of Study Design

Selection of appropriate study participants

Selection of appropriate outcome measures

Selection of the optimal experimental design

Study Participants

Given the proposed mechanism of action, who can realistically benefit? Ability to understand and participate in

the critical aspects of treatment (e.g., learn to use an assistive device)

Requirement for preserved cognitive or motor capacities (e.g., ability to dorsiflex on command)

Requirement for social support (e.g., if treatment primarily targets family support skills, employer acceptance)

Study Participants (cont.) Choose participants that vary in the the

hypothesized “treatment responsive” characteristics to clarify the mechanism? individuals with and without declarative

memory deficits in a study of errorless learning

Individuals with different degrees of social support in a study of telephone care management

Characterizing the Participants Once selected, one must ask

whether the participants in different treatment groups are “comparable” – comparable in what way(s)? Balance achieved between randomized

groups Statistical adjustment of differences in

observational studies Need prior data on prognostic factors

Comparability & Adjustment Comparability and adjustment in

terms of prognosis on the outcome measures chosen (will discuss later)

Comparability and adjustment in terms of the characteristics that predict responsiveness to the treatment under study

Outcome Measures Given the proposed mechanism of

action of the treatment, where would you expect to see treatment impact? The most “proximal” impact (as

evidence for the proposed mechanism) A more “distal” impact (as evidence

that the change achieved has clinical meaning, ecological validity)

What other factors are likely to modify the chosen outcomes?

Outcome Measures (cont.) The same treatment may be

judged effective or ineffective, depending on the outcomes chosen, e.g. case examples mentioned earlier: Oral antispasticity medications Memory remediation treatments

Outcome Measures (cont.) Should a cognitive rehabilitation

intervention have impact on: Patterns of brain imaging associated

with specific tasks? Neuropsychological test scores? Real-world activities similar to those

used in treatment? Real-world activities different from

those used in treatment? Real-world activities, performed under

distraction?

Overall Study Design Does the proposed mechanism of action

suggest a permanent effect of intervention? (parallel group vs. crossover design)

Does the proposed mechanism of action suggest “localized” or “generalized” treatment impacts? (feasibility of multiple baseline across behaviors design; utility of multiple outcomes)

Study Design (cont.) Does the proposed treatment

capitalize on neurologic recovery (early vs. late enrollment)?

Are there important covariates that might affect treatment response that should be measured?

Summary Published rehabilitation research

frequently fails to clearly describe who should benefit from which treatment ingredients, with respect to what outcomes

Theory-based treatment research has many benefits, but among them is the ability to optimize the selection of participants, outcomes, and study design

Specifying the mechanism also leads the way toward conceptualizing interrelationships among treatment outcomes

Summary (cont.) ICF provides a “meta-theory” for all

treatment research, though this theory needs to be refined into a quantitative model.

ICF predicts where we will see impact of treatments that are effective but it doesn’t give us effective treatments.

Summary (cont.) Focused domain-specific theories

provide tools for implementing change at the organ, person, or societal level.

Only programmatic research can refine the interrelationships among measurement of patient characteristics, therapy ingredients, and meaningful outcomes.