National health interview surveys for health care policy

sot .Scl Me-d Vol 26 No 2, pp 223-233 1988

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NATIONAL HEALTH INTERVIEW SURVEYS FOR HEALTH CARE POLICY CRI KARS-MARSHALL.*YVONNEW SPRONK-BOON?and MARJAN C Department

of Pubhc

Health

and

Socxal Medlcme,

Erasmus

Umverslty.

P 0

POLLEMANS:

Box

1738

3000

DR

Rotterdam, The Netherlands Abstract-Eleven Natlonal Health IntervIew Surveys (NHIS), from rune countnes

are reviewed to describe their objectives, topics and methods The NHIS-data are evaluated m terms of their vahdlty and rehablhty as well as their usefulness for health care pohcy decisions With some modlficatlons m design and methods, NHISs have potential for collectmg recent and pohcy-relevant data Suggestions are offered to improve the usefulness of NHIS-data for health care policy Key words-health use and non-use

mtervlew of data

survey,

health

indicators,

INTRODUCTION Policy declslons about health care must be based on recent data about health and sickness m a populatlon Routme data come from admmlstratlve data sources Apart from mortality statlstlcs, most of this mformatlon orgmates m health care and related mstltutlons and thus refers to a selection of the population To overcome this and other hmltatlons of this kmd of data, often additional mformatlon 1s collected through a National Health Interview Survey (NHIS) By means of a NHIS, information 1s collected from d representative sample of a country’s population to obtain subjective data on aspects related to health and dlness This paper reviews 11 NHISs with the followmg objectives 1 to descnbe these NHISs m terms of then ObJectlves, topics and methods, 2 to evaluate NHIS-data m terms of validity and rehablhty, 3 to evaluate NHIS-data m terms of their usefulness for pohcy declslons MATERIALSAND

METHODS

health

care pohcy

decision

makmg,

health

needs,

to 11 nationwide health interview surveys (in nine countries) The mformatlon for this review was collected through a computer search (VIZ Medlars, Psych Abstracts, Social Sciences Research and ERIC), consultations of the Current Contents (‘Medical Practice’ and ‘Social Behavloural Sciences’) and letters and vlslts to health interview mvestlgators m several countnes First a selectlon was made of NHISs based on the literature This resulted m a hst of mainly Western countnes where one or more NHISs were designed and conducted Then, from this group, those surveys were selected that have been recently designed and conducted (wlthm a penod of ten years) or are still ongoing m 1983 (Table 1) The results of the study were documented m a comprehensive report ‘Feeling the Nation’s Pulse A Study of National Health Interview Surveys’ [l], m which the surveys are described m terms of background, content, methodological aspects and pohcy-related aspects 0 OBJECTIVES OF NHISs

Each NHIS was started because It was felt that the existing sources of health data could not meet the great variety of needs of mformatlon about health, illness and dlsablhty Current mformatlon m most cases

In many countries, NHISs are conducted m addltlon to the existing health mformatlon system To assess the usefulness of NHIS-data for pohcy decision making, the general hterature on health interview surveys has been reviewed with particular attention

-satisfies mformatlonal needs of a purely medical nature alone, -mostly originates from medical sources and medical professionals, -does not include non-users of health services and their needs, -provides little Insight mto reasons for medical consumption, -does not provide mformatlon on life-style and environment, -does not relate sufficiently to social, economic and demographic variables

*Currently at the Institute of Cultural Studies, Umverslty of Leyden tTo whom all correspondence should be addressed $Currently at the Department of General Practice, Umverslty of Utrecht §Revlews of the surveys were sent to all NHIS mvestlgators whose studies are descrllxd m this article, with the request for comments Their reactions-mcludmg corrections and additions-have been incorporated m the final version of the report Thus article 1s essentially a summary of the revised report Since we did not receive comments from several NHIS mvestigators, we must acknowledge the posslblhty that this review article may contain mmor errors

Despite differences m content and form, all rnterview surveys, which have been investigated, have the same general objective to obtain health related 223

224

CRI KARSLMARSHALL et al

Table I The mvest~gatedNHISs m chronological order from the year of proJect development and first survev ProJect admmlstratlon

Year of proJect development

Year of tirsr survev

Stud\ frequency

Method of data collectlo”

Survey

Country

Nattonal Health Interwew Survey (NHIS) Deutsche Mlkro census (DMZ) Micro-l?conomle de la Consommatlon Medlcale (MECM) Health and Social Secunty Survey (HSSS) General Household Survey (GHS) Leefsltuatle Survey (LSS) Canada Health Survey (CHS) Austrahan Health Survey (AHS) CBS-Gezondhelds Enquete Medlsche Consumptle (GEMC) Erhebung uber den Gezundheltszustand der Eevolkerung (EGB) Socto-Medical Indtcators System (SMIS)

USA

NatIonal Center for Health Statlstlcs

1955

1957

A”“U&

West-Germany-l

Statlstlsches Bundesamt INSEE and CREDOC

1957

1957

Annuallv

I960

Ten-)cXlv

Interwe* + questmnnalres

Fmland

SOCldl,nsurance Instltutlo”

1964

I964

Irregular

Interwew

Umted Kmgdom

Office of Population Censuses and Surveys Social and Cultural Plannmg Office Statlstlcs Canada

1971

Annuallv

IntervIew

1974

I974

Three-yearlv

Intervtew

1975

1978 1971

Once (aim WdSannually) Once only

Interwew + exammatmn IntervIew

1981

Annually

IntervIew

France

Netherlands-l Canada Austraha Netherlands-2

-

-

-

Austrahan Bureau of statlstlcs Central Bureau of Statlstlcs

1977

IntervIew (sometlmes exammatmn) Interweu

West-Germany-2

Bureau lnfratest

1979

-

Once only?

IntervIew + examrnatmn

Swtzerland

SWISSNatmnal Sctence Foundatmn

1980

-

NA

Interwew+

and Kantonssprtal

mformatlon from the specific obJectIves, are

general

population

More

-to

descnbe the hvmg condltlons of the population and how these are experienced (e g Netherlands-2 [2]). -to identify high nsk areas for further studies (e g U S A [3,4], West-Germany-l [5] and Australia [6]), -to provide mformatlon about the medical consumption pattern (e g Netherlands-2 [2]. West-Germany-l [5], France [7]), -to give pohcy-makers data to help allocate resources (e g United Kmgdom [S] and WestGermany-2 [9]), -to provide social and health mdlcators based on mformatlon concernmg social and perceived needs (e g Fmland [IO, 1I], Canada [12, 131, Switzerland [ 14]), -to prepare trend analyses of disease (e g Netherlands-l [ 1S]), -to support preventive measures (e g Canada 112, 1311, -to evaluate health programmes, medlcal mterventrons and quahty of care-such as access to provlslons (e g U S A [3,4], West-Germany2 [9], Fmland [IO, 1I], Switzerland [ 141, Netherlands-l [ 151)

TOPICS

Concepts, defimtlons and operatlonahzatlons vary widely between the various countries lmplementmg a NHIS It turns out that there are as many different types of surveys as there are countries conductmg such an mtervlew survey In this sectlon. a descrlptlon

of 11 NHISs IS presented with respect to their topics, definrtlons and operatlonahzatlons The NHISs which have been Investigated are mainly descrlptlve allowmg a broad range of topics, concepts and operatlonahzatlons At the same time, most surveys have no exphclt conceptual framework from which the choice of concepts 1s derived Therefore. the content of the different surveys IS sytematlcally categorized m the global hst of topics. which IS dlvlded mto seven mam sectlons NHISs are mostly executed perIodIcally (Table I) In penodlcal data collections, new topics can temporanly be added to the core interview schedule This procedure 1s especially relevant m regularly (e g yearly) recurrmg surveys For example, addltlonal topics such as tobacco and alcohol consumption have m the past been mcluded m the American and the Bntlsh survey Sometimes when a topic becomes fashionable-smokmg m the late 70s or physlcal actlvlty m the 80s~-It IS Included m the surveys Global list of topics included In NHISs I Socro-demographic Age Gender C Income D Education E Occupation F Ethmc group G Marital status H Household/famdy I Rehglon J Dwelling K Military service

background

A B

characterlstlcs

II Health status

A General B MedIcally 1 General

defined condltlons condltlon

NHISs

for health

2 Acute/recent condltlons -behavloural effects (e g health problems causmg bed, work loss days, --specific causes (e g sickness because of pregnancy. accident), -specific (perceived) symptoms 3 Chrome/long standmg condltlons -behavloural effects (e g causmg activity hmltation, use of medlcme), -dlagnosls and doctor’s contact, *omplamts and perceived symptoms (e g type and duration) 4 Measurements (e g blood pressure, pulse, urine. weight) C Socially defined condltlons 1 Llmitatlon of activity +apaclty to function (e g reduction of performance. duration), -soaal consequences (e g bed days, effects of school, work, housework loss), -moblhty hmltatlon, and need for help (e g changes m house, need for special servlces) 2 Impairments and handicaps -general -visual impairments, -speech lmpauments, -hearing lmpamnents, -other physical handicaps (e g absence of extremltles, cause of handicap) D Mental health and well bemg (feelings, satisfaction) III Lifestyle and ruk factors A

B

Behavlour Dnnkmg (e g frequency, self-image, problems) Smoking (e g frequency, type, age started) Diet (e g type of meals on work days, changes m eating habits) Physical actlvlty (e g partlclpatlon m sports, number of hours walkmg/blcychng each day) Leisure time (e g frequency and type of leisure time activities) Preventive actions (e g seatbelt use, breast exammation) &sk factors I Physical charactenstlcs 2 Family history (e g diseases and causes of death m family) 3 Pregnancy (e g outcome last pregnancy, complaints) 4 Accidents (e g number and kmd of accidents) 5 Occupational hazards (e g working environment, noise, pollution) 6 Environmental hazards (e g transport, housmg) 7 Stressful hfe events (e g drvorce, financial problems)

IV Health A B C

knowlledge. arrltudes, opmons

Medical knowledge Attitudes towards health and disease Satlsfactlon with own health

P Health care urrllzation Consultations (doctor, nurse, dentist, other) Hospltahzatlons (e g frequency of admlsslon, duration) Use of medicines (e g frequency of prescribed or nonprescribed drug purchase and use, avadablhty of medicines at home) tests D Dlagnostlc E Maternal and child health care 1 Immumzatlons (e g timing and type of lmmunizations) 2 Use of special clinics F Preventive care 1 Check-ups 2 Specific exammatlons (e g ECG, Pap-smear, X-ray) G Use of special aids

A B C

225

care pohcy VI Health care erpenences,

A B C D E F G

arrlrudes. opmons

Avadablhty of care (e g faclhtles m vlcmlty sources of Information) Usual source of care Doctor’s delay (e g duration before doctor s contact. reason for this) Waiting-times (e g time spent in waltmg rooms opmion about this) Distances (e g travel time, problems relatmg to travelhng) Fmanclal accessibility Predictors of health care mvolvement I Attitudes toward care 2 Opmlons about care 3 Satlsfactlon with received care 4 Blood donorship (e g frequency. reasons for giving blood)

VII Health related expenses and msurance Expenses for health care (e g expenses for medlcmes. for each family member) Health care insurance (e g insurance coverage reasons for not bcmg insured) Income effects of disease (e g loss of income durmg illness) Sickness benefits and social security (e g benefits from dlsablhty insurance) Table 2 illustrates the choice of core topics meluded m the various NHISs All NHISs mvestlgated collect mformatlon on age, gender, education, mcome and occupation Information obtained m some NHISs on additional soc& and demographic uarrables allows more m-depth analyses of the relatlonshlp between background vanables and other health aspects This link between the social and health related aspects IS one of the charactenstlcs and strengths of the NHISs The measurement of health status (see global hst of topics and Table 2) 1s an important issue m the investigated NHISs Typical for NHISs IS that health status 1s formulated both m terms of the medically defined condltlons and m terms of the socially defined condltlons In the medlcal definition, health 1s conceived as the absence of physical disease The socro-medical definitions refer to the capacity to perform roles and tasks for which the person has been soclahzed [16] Most NHIS mvestlgators have avoided measuring stress and other aspects of mental health m a population Since the obJectives of NHISs rarely specify mental health this topic has only been included m four of 11 NHISs When mental health questions are however included m a NHIS (e g West-Germany-2, Canada), the mvestlgators ordmarlly employ existing questionnaires (e g the Bradburn scale of feelings) and/or questlonnalres on general well bemg and satisfaction with hfe [9, 171 There appears to be no consensus about whether and how to measure mental health status with an NHIS The evaluators of the U S A survey, as recent as 1980 were uncertain how to go about obtammg mental health data This doubt 1s lmphed m their tentative recommendation that “perhaps some data on mental health could be collected usmg a hst of symptoms related to common mental diseases and by mqulrmg about visits to ” [18] Pernon-physlaan therapists, psychologists haps the infrequent measurement of mental health status 1s a result of the lack of a short and rehable

CRI KARS-MARSHALL

226

Table 2 Core topics mcluded

m the various

Health status Socm-demographic background NHIS (USA) DMZ (West-Germany-l) MECM (France) HSSS (Fmland) GHS (Umted Kmgdom) LSS (Netherlands-l) CHS (Canada) AHS (Australta) GEMC (Netherlands-2) EGB (West-Germany-2) SMIS (Swttzerland) x = mcluded. -

er al health lnterwew

surveys

Mental health

Life-style and nsk factors

Health knouledge attitudes oplnlons

Health care utlllzatlon

Health care expenences attitudes

-

-

-

x

-

Medically and soctally defined

x

x

x

x

x

)i

x

x

x

x

x

x

x

x

x

I(

*

x

x

x

x

x

x

x

x -

x x

x

x

x

x

x

x

x

x

x x

x -

x -

Health related expenses and msurance

x -

x

x

x

x

x

x

x

x

x

x

x

x

x

x

*

x

x

x

x

x

x

x

x

x

x

= not mcluded

data-collectmg Instrument, by the difficulty of trammg mtervlewers for this addItIona task. and by the nsk that questlons about mental health could Jeopardlze the mtervlewers’ report with the respondent The shift away from curative care towards preventlon m health care pohcy declslon makmg has gradually influenced the topics chosen m NHISs For example, the number of operatlonahzatlons of health status 1s decreasing m the more recent surveys L&estyle and toprcs concernrng knowledge and attitudes

have received more attention m recently developed NHISs The defimtlon of life-style (vanables on personal behavlour) gets sometlmes broadened with nsk factors and other possible causes of disease, such as occupatlonal and envlronmental hazards, accldents and stress These factors are Important mdlcaters of changes m the utlhzatlon of preventive health care as well as curative health care Knowledge, attztudes and opmons about health are considered to be determmants of utlhzatlon of medlcal care [19] In the EGB of West Germany [9] as well as m the HSSS of Fmland [20] attitudes towards and satlsfactlon with one’s own health are considered as parameters mfluencmg access to (and use of) medlcal care and the health status of the population Measurement of utdrzatlon of health care m NHISs has at least three important charactenstlcs 1 The types of health services used (hospitals. physlclans, dentists) 2 The purpose for which they were used 3 The unit of analysis with which the use of the service 1s measured number of contacts with doctors, volume of services, episodes of illness etc [19, p 1011 Next to questlons on utlhzatlon of care, m a number of NHISs, mfonnatlon IS collected on knowledge, experrences, attmdes, and opmons concernmg health care In two surveys it IS defined m terms of the degree of access to medlcal care, the posslblhty to

consult a doctor of personal choice at his surgery and charactenstlcs of the most recent consultation such as waltmg times, satlsfactlon with the consultation and duration of the vlslt [7, 211 Reason for this IS the argument that “ use (of health care) IS dependent on the predlsposltlon of the mdlvldual to use services, his ablhty to secure services and his illness level” [ 19, p 1071 Anancral factors are consldered to be a maJor determmant of the use of health services One survey (The HSSS of Fmland) was actually mltlated to explore the relation between economic precondltlons for use and the actual use of medlcal services The mtroductlon of a national health insurance almed to establish a “ greater equity m the use of the health services among various population groups ” [lo, p 31 The natlonal health Insurance scheme only contributes to the social secunty through economic means, 1e by lowenng the price for health services and by compensatmg for the loss of Income In a number of NHISs, questions are asked about the family’s own funds which are spent on health care and reimbursement paid by Insurances [22] METHODOLOGY

Design

Most NHISs have a simple design They are descnptlve and are not intended for testing hypotheses The Fmland and West-Germany-2 studies are exceptions The Finland survey IS more testing m nature m view of the hypotheses that have been formulated In addition It has an evaluative component, assessmg the success of the sickness insurance scheme, and measuring the long-term Impact of the Public Health Act, m Fmland [23] In the West-Germany-2 both a hypothesis-testing (m relation to an mterventlon study) and a descnpttve approach (for supplying background mformatlon for mterpretatlon of data) are used [9]

NHISs for health care pohcy

NHIS mvestlgators have not yet tried to mcorporate a quahtatlve approach, for example addmg mformatlon from m-depth mtervlews and/or case-studies Such an evolution however, would follow the current trend m social pohcy research, where quantitative data are mcreasmgly bemg supplemented by quahtatlve data [24] One of the reasons for not mcludmg case-studies and m-depth interviews 1s that they are highly labour intensive and thus expensive

127

Data collectlon

The face-to-face interview 1s currently the most common technique m NHISs However this approach 1s often complemented with questlonnalres that are left at sampled households by the mterviewer In France. for example. a booklet 1s left behind with the request for respondents to fill out all medical expenses, mcludmg all medicine and pharmacy expenses, for a penod of three weeks between visits of the interviewer [7] Also m Switzerland a questionnaire 1s left behind to be filled out after the Samplmg mam interview, with questions focussmg on resThe NHISs fall mto two categories those surveys pondent’s partner and two youngest children, if using the cross-sectional approach and those using present [14] Alternative approaches to data colthe panel-approach In most NHISs, the crosslection also deserve attention, especially if they are sectional approach of collectmg data at one point m much less expensive than the face-to-face interviews time 1s employed The panel approach IS seldom The telephone interview 1s one such alternative, but mentioned m the literature on health interview has not been used m the surveys. which have been surveys The West-Germany-2 though, 1s a panel investigated However, m a U S A -pubhcatlon of study, comparing the same measurements for the 1979 the mltlatlon of the THIS (telephone health same sample at several different points m time interview survey) was revealed by the National There 1s not much literature available, evaluating Center for Health Statlstlcs (NCHS) Such a survey the sampling strategies employed m NHISs In one of would enable the NCHS to quickly satisfy demands the few cases that literature 1s available, an evaluation from the Public Health Services about issues rereport of the U S A study [18], no changes m qun-mg instant attention, such as use of saccharine, the sampling strategy are considered necessary All hquld protein diets and changmg patterns of cigarette NHISs employ a household sample selection with the smoking [25] In addrtlon to advantages wrth regard mdlvldual as the unit of observation and analysis to costs, flexlblhty and reduction of the non-response Generally (e g the survey of Switzerland excluded) from people who refuse to let mtervlewers mto their NHISs exclude the mstltutlonahzed groups within the homes because of a mounting fear of intruders, the population such as people hvmg m hotels, large telephone interview 1s considered to have the advanboarding houses, hospitals, boardmg schools, halls of tage of identifying mdlvldual errors more quickly and residence, military barracks, pnsons This can be the accurately than other methods [25] On the other result of the sample procedure which 1s used m health hand people without a telephone will be excluded and interview surveys, e g use of an electoral register or people over 65 years old may be overrepresented telephone book to establish the samphng frame It 1s because they are more likely to be at home to answer generally acknowledged that by excluding the mstltuthe telephone In addition, issues such as alcohol, tlonahzed part of the population an overall picture of tobacco and drug use may be too sensltlve to ehclt the total population can never be obtained data m a telephone dlscusslon The sampling strategies vary among countries In Many NHIS mvestlgdtors allow proxy interviews, the U S A a multistage highly stratified probability usually held with a member of the household to sample 1s drawn of approx 40,000 households. obtain mformatlon on other members of the same approx 110,000 respondents are interviewed yearly household Provlslons for proxy interviews are taken For a smaller country hke Switzerland, the represenwhen selected persons are not at home or incapable tatlve sample (through the voter’s register of the of responding or are children under a certam age The Swiss population) of 4000 people 1s chosen m prodecision to allow proxy interviews depends largely on portion to the dlstrlbutlon of the Swiss population the use thdt 1s expected to be made of the data Given m German (66%), French (18%) and Italian speakthe large amount of other NHIS data, a separate mg (15%) Roughly one m every 1250 people 1s analysis of proxy data may not be considered worth interviewed [14] the effort The philosophy about proxy use differs by country While m the United Kingdom proxy mterTlmrng views are only accepted as a last resort, m France they are used as a standard practice Next to the perlodlcal execution of NHISs (as Most NHISs use structured questions with prementioned before), another aspect of timing can be coded answers This requires an extra effort in the dlstmgulshed m NHISs The data collection can be design phase of the interview schedule to prepare either contmuous (I e 52 weeks during the year) or The advantage, non-contmuous The U S A study and the study of exhaustive response categories though 1s that respondents’ answers are lmmedlately the United Kingdom are examples of a contmuous recorded m appropriate categories A few questions data collection. an approach which ehmmates bias m allow open responses, which permits the collection of the data caused by seasonally or perlodlcally varying more and richer data than preceded questions would condltlons However, the non-contmuous approach ehclt, and gives the respondent more freedom in 1s chosen more frequently The non-contmuously answering But this means more work and sklll for executed studies can collect data on a one-shot basis the mtervlewers-writing down the answers veror on several occasions In France, for example. data batim, and for the mvestlgators-interpreting and were collected from the same respondents five times. within a period of three months classlfyrng the answers

CRI KARS-MARSHALL

228

The Interview schedules developed for most NHISs contam large numbers of questions (between 80 and ISO), because of the many topics that the mvestlgators feel should be covered Selecting and tramng the mteruewer

On the whole the NHIS hterature pays httle attentlon to selecting, trammg and supervlsmg the mterviewers Exceptions are four reports of studies by Cannell [26] conducted m connectlon with the survey of the U S A The cntena for selecting mtervlewers vary somewhat among the 11 NHISs reviewed for this paper In the United Kmgdom and U S A studies, the mtervlewers are required to be females, m the France survey no sex preferences are stated, but interviewers should be professionals, speclahzed m the field of medicine [7] In Australia, the criteria were said to be mtelhgence, potential for commumcatlon and a willmgness to work at night [6] In the West-Germany-2 study, a special group of younger mtervlewersbetween 12 and 18 years old-was selected and tramed to mtervlew respondents m the same age group [91 Most interview schedules are accompamed by mterviewer instructions Specific information on mterviewer trammg IS lacking, however, for example on mtroducmg the study and reassunng the respondents Cannell and Kahn emphasize that respondents require early reassurance about ‘the Interviewers’ Identity, the legltlmacy of the research, the process by which they were chosen for the Interview, the protection which they may expect as respondents, the extent of the demands which are to be made upon them and their own adequacy to meet those needs ” [27] VALIDITY

AND RELIABILITY

VahdltJ

Few studies explicitly assess the validity of data which are obtained m large scale mtervlew surveys on health and health related topics among the total population The vahdlty-studies which have been published relate either to very small groups of persons [28], to hospital or other patient populations [29] or to one specific topic [30] To Illustrate this, various articles focussmg on topics which can be included m a health interview survey are summarized m the review of NHISs [I] Some of the observations are reported below Crzterlon vallduy The vahdatlon studies which have been published mostly assess the vahdlty of interview data by comparmg data from interview surveys with data from medical records, from medical exammatlon surveys or from doctor’s reports This type of vahdlty 1s commonly called LLcrlterlonralrdIt)“’ [31-331 The medical records, findings of medical exammatlon surveys, or doctor’s reports serve as cntenon for assessing whether the mtervlews really measure what they intended to measure In several studies the interview score on physical performance [34] on acute and chrome diseases [35-371 on dlsabllIty and lmpamnent [37], and on use of health faclhtles [36,38, 391 showed a slgmficant agreement with medical records, doctors statements and/or medical

et 01

exammation In other studies the percentages of agreement on the prevalence of chronic diseases vaned widely [30,40,41] In addition data of health interview surveys were rather considered as accurate predictors of issues m which health planners are interested (e g utlhzatlon), than as mdlcators of real health status 1401 Those studies have concluded that questions on chronic diseases are generally non-valid and that interview surveys are an unsuitable means for measunng chronic diseases m terms of dlagnosls Exceptions are the Rose questionnaire on lschaemlc heart disease [42] and the British MRC questionnaire on respiratory condltlons [43,44] Those questlonnarres appeared to be highly specified and reasonably sensitive [42-451 Concerning life-style (e g dnnkmg and smoking hablts, use of drugs), with a few exceptions [46,47], the studies only concern assessing the rehablhty of the data No clmlcal tests have been carned out m order to assess the vahdlty [48] Non-response Failure to obtain mformatlon on selected persons Identified by the samphng scheme 1s a problem confronting all NHISs and has consequences for the vahdlty of data In the literature on health interview surveys this non-response problem IS often mentIoned The reported percentages of response vary sigmficantly among countries [from 95% m U S A (1974) to 83% in the United Kingdom (1971) and 72% m France (1970)] This IS probably caused by different defimtlons of response-rate As the Bntlsh study reports [8], response-rate can be defined as The mmlmum response rate, including only those members of the household who fully cooperate The maximum response rate, counting all partially cooperating members of the household The middle rate, including all partially cooperating members of household, wtth the exception of those households where no proxy mtervlewers could be held with members who were absent or refusing the interview In most reports of this study, the latter response-rate 1s used It IS not clear which definition IS used m the other NHISs In theory, if accurate estimates on non-respondents’ answers could be obtained, this vahdlty problem could be dealt with easily But such estimates are llluslve As Banks and Frankel state “m most data collectlon there IS no practical way to find out what would be the responses of all non-respondents, so there IS no way to determine the Improvement m the estimates caused by non-interview adJustment” [49] Investigators’ bias Although not described as such m the NHIS literature, mvestlgators from various dlsclplmes may introduce a validity problem m the analysis and interpretation of the NHIS data The health interview survey method has been adopted because of users’ dlssatlsfactlon with existing mformation sources-focussmg on oblective data-on health and uses of health care Thus subjective data have been collected about perceptions, attitudes, values, practice, but also about complamts and symptoms The medical and non-medical mvesttgators involved m interpretation of the data (as well as of course less knowledgeable users of the data) may fall

229

NHISs for health care pohcy

mto the trap of treatmg subJectlve data as if they were obJectlve, and may be tempted to draw conclustons about incidence of health and disease based on subjective data Rehabdrty Reprodmbdtty IntervIew data, m order to be rehable. at least have to be reproducible In some studies the rehablhty of mtervlew data proved to be sattsfactory These studies concerned the topics headache [SO], chrome condltlons [37] and acttvlty hmltatlon [Sl] The rehablhty of data may depend on vanatlons m answers of the respondent, m the measurmg Instrument Itself or m the interviewer [31,X1 Recallperroak Smce most NHISs are retrospective, mvolvmg recall periods of one week up to one year, collectmg accurate data can be a problem For each topic there seems to be a different penod to which the respondent should refer m answermg the questions Little mformatton exists m the NHIS literature about the optimal recall penods But others have studied the issue For example, for the recall of the motor vehicle acctdents the opttmal penod was found to be three months [52] The best data on the use of health servtces by chtldren were obtained by havmg the parents keep a health calendar for four weeks, smce this was an expensive method, the second best solutton was a two week recall period. followed by one of 12 months (531 Proxy zntemews Most survey designs allow proxy mtervlews, but for instance m the Umted Kmgdom a proxy interview IS a last resort and a number of questtons are not asked when the proxy sltuatton IS hkely to influence the rehablhty of the answers To obtam consistency m the data of the dtfferent household members and to allow stmphctty m the analysis, It seems advtsable to follow one strategy, e g only proxy or only personal mtervtews However, m proxy data some bias IS hkely to occur A study of the late fifties showed that when an mdtvldual was personally interviewed It was twice as likely that certain diseases were mentioned than when a proxy respondent was mtervlewed On the other hand some diseases were mentioned more often m the proxy mtervtews than by the respondents themselves [54] Wtth regard to data of Importance for mother and child care, Kosa et al (551 reported that the mformatton from the mothers IS useful but mostly mconststent Accordmg to Schach and Starfield [56] mothers tend to mention only certam diseases and the moment of onset of the Illness, prevalence and senousness would be mlssed Question related aspects Various attempts are made to achieve an opttmum response, even when the respondent has actually agreed to the mtervtew Three methods for mcreasmg the response m a survey have been mvesttgated [57] The methods concerned

1 the amount of mformatlon on the content of the study presented to the respondent m the mtroductlon to the mtervlew, 2 the guarantee of confidentlahty given to the respondent, 3 the request to the respondent to sign a form which contamed mformatlon on the study It turned

out that only the latter request

for a

signature appeared to have a significant effect on the response rate for the interview schedule as a whole, because those who refused to sign appeared to be more mclmed to give either unsatisfactory or no answers to some personal questlons The best effect on the response rate was obtained when the respondent was Informed, prior to the mtervlew. about the request for a signature after the mtervtew was over The answers of respondents may be distorted by two kmds of questions 1 questions iour), 2 questions

ehcltmg fear (e g on Illegal behavon socially desirable behavlour

[58]

With regard to formulating questtons on hfe-style (alcohol, drug use), these tssues should be taken into conslderatlon Internewer bras To learn how to muumlze bias that may be created by mtervtewers’ behavlour, studies were undertaken m conJunctIon with the U S A study [59] They focussed on 1 the behavlour of the mtervlewer and his/her mteractlon wtth the respondents durmg the Interview. 2 differences m behavlour of the vartous mterviewers, with related tmphcatlons for supervmon and trammg, 3 the use of verbal remforcement by the mtervtewer durmg the mtervlew One expenment examined feedback given to the respondent by the mtervtewer-an encouragmg smile, thankmg hrm for mformatton or clanfymg a questlon The research showed. that by butldmg feedback circumstances mto the survey, more complete mformatlon can be gathered with the approprtate feedback, both of a posltlve and a negative nature 1591 USE AND NON-USE OF NHIS DATA It IS not always clear what tt means to ‘use’ survey the data Is ‘use’, as Weiss and Bucavalas ask, “ adoptton of research recommendattons m fact, the nudging of a declslon m the dtrectlon suggested by research findmgs, the reinforcement of a likely decision by research, the conslderatton of research findings, rethmkmg the nature of the pohcy Issues, redefining mformatlon needs? What kmd of ‘use’ IS real use? And how much IS enough?” (601 For this dlscusslon we wtll refer to use of NHIS data as the constderatlon and apphcatton of research findmgs for health pohcy declslons But there are virtually no records of how health pohcy dectstons have been made, or what mformatlon went mto the polsymakers’ dehberatlons Thus it 1s not easy to determme how, or even If, NHIS data have been used In some cases, however. It IS clear Finland drafted a Pubhc Health Law, butldmg on NHIS data and claims that health mdlcators have been developed usmg the survey data [IO, 611 The U S A federal government, usmg (among other thmgs) estimates of the use of health care services from the U S A -survey, formulated the leglslatton for both the Medicare and Medtcald programmes [I81 For other

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KARS-MARSHALL ef al

examples of ‘use’ given m the literature, It 1s less clear what the data have contributed to pohcy decision makmg, e g a statement such as, “the addltlon of a senes of questlons relatmg to smokmg hablts has provided the Office of Smokmg and Health with estimates on the smokmg status of persons m the USA” [18], implies use of the data for statlstlcs, but does not provide an mdlcatlon about any decision made as a result of these data No evidence could be found m the literature that other NHISs have been Instrumental in pohcy or programme formulations, few studies have attempted to assess the use of NHIS data [exceptions are 62,631 What can be the reasons for non-use of NHIS data? As Woolsey and Pernn [63] have pomted out, “Too often statlstlcal systems are deslgned and operated by statlstlclans who have not established channels for real commumcatlon with the planners, pohcymakers and programme managers expected to use the statIstica results The tables of results from the systems become an end m themselves ” Two factors seem to pomt at reasons for potential non-use of data

been developed m close collaboration with pohcymakers-may not be famlhar to all potential users In such cases special efforts are needed to alert pohcymakers at all levels about the existence of the data Presentation of the NHIS data to the users Vanous approaches to make the mformatlon accessible are found among the NHISs In France and England a smgle volummous report 1s produced, while m Austraha and m the U S A various smaller reports are pubhshed No mformatlon seems to exist. however, about policy-makers preferences for the most efficient and effective manner of commumcatmg the results For example, It IS not clear whether pohcymakers are given a choice about the way they prefer to receive their data The mvestlgator could provide raw data for further analysis, or frequency tables, a monthly report or an overvlew of avallable data that could be further analysed upon request Woolsey and Perrm [63, p 31 have recommended for the U S A study “to tram admmlstrators m the use of statlstlcs and to index the avallable data m order to Improve the effectiveness of the data system, the plannmg process and the usefulness of statlstlcs” This suggestlon recogmzes that also on the recelvmg end the 1 the data collected are Irrelevant, necessary preparations are still needed, to use data 2 the data collected may be relevant, but users effectively have no access to it Another issue m this context seems the role of the The collection of irrelevant data can be the result of mvestlgators Is the objective of the study to make a lack of commumcatlon between mvestlgators and pohcy recommendations or to merely provide sepotential users about pohcy questions that need lected data? In most NHISs It appears that the answers To Improve this commumcatlon, m an mvestlgators have chosen for the latter objective evaluation study of the survey of the U S A , It IS Therefore NHIS data are destmed to be presented suggested to develop a standard procedure for dataand treated as an ‘Encyclopedia’ [65], rather than as requests which should supply mformatlon on “the recommendations for health care pohcy develpurpose, geographic unit of representatlveness, prosopment pcctlve users and expected uses of data, the desired Avadabdlty of up-to-date mformatlon The more frequency of mcluslon m the NHIS, the reason why frequently conducted NHISs (e g annually) have a other methods of collectmg the data are less satlsgreater chance to provide users with up-to-date mforfactory than the use of NHISs” [ 18, p 171 matlon than those NHISs undertaken with longer Only m five mtervlew surveys does a regular conperiods m between However, even then delays with tact exist with departments and other pohcy mstltudata analysis caused by large amounts of data may tlons to discuss data needs which may lead to the prevent the mformatlon reachmg the pohcy-makers mcluslon of certam topics m the surveys This contact at the appropriate moment takes form m inter-departmental commlttees (Umted Fmally, Coleman’s suggestion that “It 1s better to Kingdom) [8], general advisory commlttees (U S A ) have partial mformatlon available at the moment [4], a ‘consultative task force’ supervised by parhathat actlon should be undertaken, than complete ment and department(s) (Finland) [lo] or a ‘Jomt mformatlon afterwards” [66], seems a valuable sugproject team’ of department and research/statlstlcal gestlon, and d followed up should help prevent bureau with shared responslblhtles (Canada) [ 121 non-use of NHIS data For the Dutch GEMC a task force has been appointed conslstmg of the executmg orgamzatlons and CONCLUSIONS AND SUGGESTIONS some pohcy agencies This team was assigned to adv:se the executmg orgamzatlon (m case the Central Obviously, if a NHIS IS expected to be of practical Bureau of Statlstlcs) on design and content of the use, Its objectives should be developed by the mhealth mtervlew survey [64] In the other mtervlew vestlgators m close collaboration with the users and surveys a more autonomous posltlon has been adopits data should have been exphcltly mvestlgated on ted m relation to pohcy officials theu vahdlty and rehablhty In general however, the research obJectIves are very broad and not duected at Non-use (or use) of data IS also. m part a function of the access the user has to the mformatlon Access answering clearly defined pohcy questlons If pohcymvolves awareness of data, that IS m an accessible makers are Involved, they often have dlfficultles m format and up-to-date ldentlfymg problems and mdlcatmg the specific needs for data The result IS that frequently mvestlgators m Awareness of the ewtence of the data For most NHISs that have been gomg on for several years lsolatlon decide on the choice of concepts, their already, e g the U S A and the England study, the defimtlons and operatlonahzatlon, the data-analysis potential users are hkely to be aware of this source and mterpretatlon of data Newly deslgned NHISs--lf they have not The aim of a NHIS should be to provide recent,

231

NHISs for health care pohcy relevant, valid and rehable data to health pol~ymakers that ~111 help them make decwons Three mam obstacles to achlevmg this aim are that -the data are not available, -the data collected are mapproprlate or madequate, -the data are good. but poorly commumcated What can NHIS mvestlgators do to overcome obstacles? We have three suggestlons

these

1 Work closely with the users (pohcv-makers) the NHIS data

of

a Identlfv data needs m advance Before the survey IS designed, estabhsh close contacts with pohcymakers to -help them state health problems clearly and ldentlfy data they need for answermg specific pohcy questlons, -obtam their mput m plannmg the design, analySIS and reportmg phases of the NHIS Declslons should be made collectively example. such Issues as

regardmg,

for

-will the study be descnptlve or hypothesis testing’ -are contmuous or non-contmuous data desired? -what core or ‘speaal Interest’ topics should be mcluded m the NHIS? -what are pnonty topics for health care pohcy declslon makmg? -wlthm which time frame are the data needed, and 1s this feasible? Help mitlate the development of an ongoing feedback system through which pohcy-makers can regularly Inform mvestlgators about their data needs b Determme data presentation Before the data are analysed and reported -the audtences for the data should be defined, and If necessary the data should be presented m different pubhcatlons, -the presentation of the data should be determmed, e g should have the form of an ‘Encyclopedla’ (rough data on computer prmt-outs, tables with or without mterpretatlons which people can consult any time) or only recommendations for pohcy declslon making should be made (e g reports focussmg on specific pohcy questtons, supplemented by recommendations for action)? 2 Include tlahdrtv and rehabdrtv checks rn each NHIS Users of NHlS should know the degree to which the data 1s rehable and vahd Investigators shouldas part of their reports-descnbe how vahdlty and rehablhty have been assessed Moreover, mvestlgators should dlfferentlate clearly between sublective and ObJectlve data, and treat them accordmgly m the data analysis and mterpretatlon 3 Acotd re-wwentlng the NHIS n?heel Make systematic NHIS mvestlgators

efforts to build a network among around the world, so they can

exchange expenences about research methodology, specifically about

design

and

-formulation of obJectIves. -sampling strategies, -concepts, defimtlons and operatlonahzatlons. -appropriate date collection Instruments. --Interviewer selectlon and trammg. -data vahdatlon. -new topics for which no reliable methods are yet avaliable (e g drugs use) Countries consldenng the lmplementatlon of a NHIS need to know If such a NHIS 1s the appropriate method to obtam mformatlon for health care pohcy development The answer seems ‘yes’ If -currently existing sources of mformation are not sufficient or vanous small local surveys could be replaced by one larger national study, -NHIS mvestlgators and data users can get together and collaborate closely m all phases of the study, -hmltatlons of NHIS data are acknowledged and thus expectations of the outcome are realistic, -costs of the survey are reasonable, dlssemmatlon of the data 1s planned in advance, and allows potential users easy access Acknowledgements-First of all, we would hke to thank the researchers from the various NH& reviewed. for their help m provldmg us with the necessary literature and useful comments wlthout which our study could not have been carned out Furthermore we are grateful to Paul .I van der Maas and John F Marshall, who have made constructive comments on drafts of this article This research was supported by the Muustry of Health and Envxonment and by the Erasmus Umverslty, Rotterdam At the time of the study all three mvestlgators were affiliated with the Department of Public Health and Social Medlcme Erasmus Umverslty, Rotterdam, The Netherlands REFERENCES

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Consumptle

van

de

Ge:ondheuisenquCte

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