Evidence and Information for Policy Health as a multi-dimensional construct and cross-population comparability Colin Mathers (WHO) on behalf of Taskforce on Health Status Working Paper No.1 22 November 2005 STATISTICAL COMMISSION andSTATISTICAL OFFICE OF THE UN ECONOMIC COMMISSION FOREUROPEAN COMMUNITIES EUROPE (EUROSTAT) CONFERENCE OF EUROPEAN WORLD HEALTH STATISTICIANS ORGANIZATION (WHO) Joint UNECE/WHO/Eurostat Meeting on the Measurement of Health Status (Budapest, Hungary, November 2005) Session 1-Invited paper

Evidence and Information for Policy Background Previous meeting (Geneva May 2004) –Broad agreement on approach –Taskforce set up to develop proposals for instrument –Also to further articulate the arguments supporting the conceptual approach Taskforce has prepared three papers –on conceptual approach –criteria for choice of domains, and –proposals for items This talk will give overview of paper 1

Evidence and Information for Policy Outcome of Geneva 2004 meeting Focus is on measurement of health states of individuals in surveys This requires a multi-dimensional approach: a focus on a core set of domains of functioning rather than on a single global question Measurement focus is on an individual's capacity to function in each domain.

Evidence and Information for Policy Rationale for further articulation To support the instrument development process, it is important to have: –a clear conceptual framework for defining and choosing health domains –clear and unambiguous definitions of what it is intended to measure in health domains

Evidence and Information for Policy Overview of issues addressed Health status and health states Multi-dimensional approach ICF as the framework What should be measured in domains Distinguishing health states from determinants and consequences Health states as attributes of individuals Cross-population comparability

Evidence and Information for Policy Health status and health states

Evidence and Information for Policy Health status and health states Health states: functioning in a set of domains "right now" Health states may potentially include some or all ICF categories, not just the parsimonious set chosen for measurement Health status: includes health states, diseases and injuries, mortality risks, physiological risk markers and POSSIBLY health prognosis, resilience, risk factors.

Evidence and Information for Policy Health trajectories and health states B Physically fit, unipolar depression during younger adult ages A smoker, atherosclerosis from age 45, later heart disease C HIV positive

Evidence and Information for Policy Mobility AffectPainCognitionSelf-Care Usual Activities Domains of health

Evidence and Information for Policy Mobility AffectPainCognitionSelf-Care Usual Activities Overall level of health Domains of health Health state valuations

Evidence and Information for Policy Summarizing the measurements v = f (c 1, c 2, c 3, ……., c n ) summary index of health state + indicators for mortality risks by cause, age, sex etc + indicators for disease and injury causes + indicators for risk factors and determinants + indicators for health interventions + indicators for other aspects of well-being/quality of life + ….. Mobility AffectPainCognitionSelf-Care Usual Activities Domains of health (c 1, c 2, c 3, ……., c n ) Health state profile Health status

Evidence and Information for Policy Multi-dimensional approach During the last three decades, there has been general acceptance of an approach to describing health states and disability of individuals in terms of multiple domains of health, and in developing self-report instruments that seek information on each of these domains

Evidence and Information for Policy Examples of health domains

Evidence and Information for Policy Health State Descriptions Mobility AffectPainCognition Vision Hearing VitaityDigestion Core health domains – common to most instruments Other potential health domains Skiing Inter- personal

Evidence and Information for Policy Challenge for the development of a health state interview instrument Identify the most parsimonious set of health domains with the highest explanatory value. Mobility Vision Hearing Communi cating Universe of health domains Cognition Interpersonal relationships ???? Skiing?

Evidence and Information for Policy International Classification of Functioning and Health ICF

Evidence and Information for Policy ICF as the framework Provides conceptual underpinning (universe of domains, plus impairment, capacity and performance) Provides a starting point for identifying a parsimonious set of domains These may be domains, subdomains or items in the ICF classificatory framework Does not provide guidance on which domains are core 'health' or parsimonious

Evidence and Information for Policy What should be measured in domains Body functions and structures  impairment Activity/participation domains  Capacity OR Performance Measurements of these quantities must at minimum be for ordered categorical values Quantity should map to a unidimensional scale (observed or latent, ordinal or cardinal) not mix two or more dimensions

Evidence and Information for Policy Capacity versus performance Performance measures difficulty in doing domain tasks in the current environment Capacity measures difficulty in doing domain tasks in a standardized environment eg. for seeing a standard environment might involve clear air and normal levels of good lighting Performance changes with changes in the environment, whereas capacity does not How far does a questionnaire need to go in defining normative environment?

Evidence and Information for Policy Determinants and consequences Important to distinguish health states from determinants and consequences The same determinant may be associated with different health states in different individuals The same health states may be associated with different levels of well being and quality of life in different individuals

Evidence and Information for Policy Environmental factors Causes of health states Mobility AffectPainCognitionSelf-Care Usual Activities Underlying disease and injury causes according to ICD rules HIV/AIDS Diabetes Panic disorder Road traffic accident Health state

Evidence and Information for Policy Environmental factors Causes of health states Mobility AffectPainCognitionSelf-Care Usual Activities Risk factors HIV/AIDS Diabetes Panic disorder Coronary heart disease Disease and injury causes Health state Unsafe sex Smoking Physical inactivity Overweight Road traffic accident

Evidence and Information for Policy Attributes of individuals Health states are individual attributes Measured at individual level (not at level of body parts, or of groups such as families, households, cities etc) Aggregated across individuals to produce summary information for population groups (eg. prevalence rates for difficulties in domains, average levels of domain capacities etc)

Evidence and Information for Policy Cross-population comparability Same measurement set (domains, capacities, scales etc) Same questions and instruments - cultural and translation issues Addressing the fundamental problem of comparability of use of response categories eg. does 'moderate difficulty' in mobility mean the same thing to a 80 year old and a 20 year old, to an American and a Chinese? Addressed in more detail in later session

Evidence and Information for Policy Operational issues Time frame for questions on current health state How explicit do we need to be in survey questions on distinction between capacity and performance? What about aids and appliances, eg. hearing aids, glasses, contact lens

Evidence and Information for Policy Terminology Health status -- used generally to refer to all measures related to health (diseases, health states, mortality risks, risk factors?, prognosis? ) Health state – capacities of an individual in all important domains of health Health profile -- a vector of capacity scores for important domains of health Health state valuation -- a preference based single cardinal number summarizing the health profile Quality of life measure -- refers to a broader class of appraisal measures that may relate to health status, wellbeing, satisfaction or utility

Evidence and Information for Policy Agreement on a common framework for measuring health status Health states are an multi-dimensional attributes of individuals Measurement of health states  determining capacities of individuals on multiple domains of health Functioning within health domains is conceptually distinct from overall well-being or quality of life Health states must be kept distinct from determinants and interventions