am j clin nutr 1971 balogh 304 10

8/14/2019 Am J Clin Nutr 1971 Balogh 304 10

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30 4Th e A m e r ic a n Jo u r na l o f C lin ic a l N u trition : M A R C H 1971 pp . 304-310. Printed in U .S .A .

R andom repeat 24 hour d ie tary recalls

M iriam Balogh H arold A K ahn2 and Jack H M edalie3

T he presen t state of the art o f co llectingdietary data on individuals fo r ep idem iologicpurposes has been w ell sum m arized by M o-

jonnier and Hall 1 w ho report that directm easurem ent of food intake is feasible only

fo r sm all g roups; that food diaries m ay causethe subject to change his norm al eating

habits; that general histories are subject toproblem s of m em ory ; and that although 24-hr recall histories m ay be m ore objective than

general histories, they suffer because only 1day is m easured. A gainst this background the

present paper investigates the results obtained

in repeating a 24-hr recall interview on

several random dates.

jective

W e w anted to learn m ore about the 24-hrdietary recall as a tool for es tim ating dietary

in take, w ith particu lar atten tion to the size ofthe error in m easuring average intake in re-

lation to the num ber of days that data were

collected. In addition , w e w anted to com pare

the repeat 24-hr recall w ith thehistory ofusual dietary intake.

Method

O ne hundred volunteers were selected from them ale civil service em ployees who w ere taking partin the Israel Ischem ic H eart Disease Project 2and attending the Jerusalem Clinic for their thirdm edical exam ination early in 1968. For ease ins tudy operations subjects w ere lim ited to thoseinone of the three fo llow ing offices: the M inistry ofFinance, th e Custom s O ffice, and w orkers in theK nesset Israeli Parliam ent . M en in these officesare pr incipally cler ica l an d adm in istrative w ork ers .T hey w ere told th e ob jectives of the s tud y and

that, if included, we w ould contact them on arandom day once a m onth to inquire in detail w hatthey had eaten on the preceding day. W e specifi-cally d iscouraged those who felt unw illing or un-able to keep up th is schedule for a full year.

The persons w ho consented to take part w ereim m ediately questioned about their usual food in-take. The questionnaire used was the sam e shortquestionnaire that w as designed for the Israeli

lschem ic H eart D isease Pro ject in 1963 3 .Ceram ic food m odels in three sizes were used forfoods, the sm allest size w as counted as a standardunit, the m edium size was equivalent to twounits and the large size to three units. O ther foodm odels m ade use of natural products in threesizes nuts, olives, candy , seeds, chocolate, etcetera . Sim ilarly cu ps, glasses, p la tes, an d sp oon s

w ere also displayed in different s izes to m ake it

eas ier for th e sub jects. A food table based on thatused for th e Israeli Isch em ic H eart D isease Proj-ect 4 w as used in conjunction w ith m ultip liers

representing the num ber of standard portions ofeach food reported. U nusual foods or special re-cipes w ere hand calculated by the nutritionist in tobasic nutrients and these w ere then punched foraddition to the nutrients derived from the report o fstandard foods. Nutrients were calculated the sam eway for both the dietary history of usual in take andthe m onth ly 24-hr recall histories now to bedescribed. O n a random ly chosen day in eachcalendar m onth, the nutritionist asked for ap-pointm ents with several vo lunteers in a particu laroffice. In the arrangem ents for in terv iew s w e w ereassisted by a contact m an in each location. Sub-jects were asked to com e at an agreed tim e to thein terv iew room w here the food m odels were ondisplay. The interview proceeded through a recol-lection of the activities of the previous day w ith a

s t o p fo r details at each eating period. After th isquestion ing, the nutritionist repeated to the sub-ject the m enu for the whole day and cross-checkedhim with questions like: D idnt you eat any fruityesterday? D idnt you have any eggs at all?

If they were in the office, subjects were ques-tioned each m onth except A ugust during theyear beginn ing M arch 1968. Every effort was m adeto interview the subjects on the sam e day con-

Israel Ischem ic H eart D isease Study, P .O.B.2631, Jerusalem , Israel. H eart andLung Institu te, Bethesda, M aryland . D epart-m ent of Fam ily M edicine, Tel A viv U niversity,Israel.

The study began w ith random ized dates as-signed to each participant but because of special

office conditions it was not practical to continuew ith random assignm ents. The actual dates selectedfor contact in any one office represented acom-plex interaction of all relevant facts regarding thethree offices e.g., subjects m ight be interview ed inone office because the in terv iew room inanothero ff i c e was unavailable that day . To the best ofou r kn ow led ge, in terview dates w ere not predict-

ab le b y the sub jects them selves.


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RA ND OM REPEA T D IETARY R E C A L L S 305

TA BLE 1

N u m b e r o f s u b j e c t s p r o v i d i n g s p e c i f i e d

n u m b e r o f 2 4 - h r d i e t a r y histories

N umber o f reports (or more) N umber of subjects

2 90

3 87

4 84

5 846 797 73

8 719 50

10 2811 (exactly) 12

tacted; if this w as impossible, no substitute dayw as chosen. Therefore, no report on the subjects

intake for that month w astaken. The study coversw orking days during all seasons of the year, in-cluding days of slight indisposition w hen subjectscomplained ofhaving a common cold, indigestion,or w ere not feeling too w ell. For each subjectan attempt w as made to include tw o interview sfalling on a Sunday orafter holidays so as tocomprise food eaten on the Sabbath or on a holi-day.

A comment on the use of vo lunteers may behelpful. If w e w ere try ing to estimate the diet o fIsraeli male civil service w orkers, w e w ould nothave chosen volunteers, but w ould have tried toselect at random members of that population. Butour objective is different. W e w ant to learn some-thing about how people vary in day-to -day nutrientconsumption and about the relation betw eenw hat they report eating usually and the average

of w hat they report eating on several specific days.Our efforts in this study are not directed tow ardmeasuring individuals representative of other per-sons in the population but to measuring dietary in-

TA BLE 2

take for specific days for an individual in an at-tempt to obtain data that are representative of theannual dietary intake for that indiv idual. A sknow ledge accum ulates and questions become moreprecise, randomization so as to permit generali-zation to the popula t ion sampled w ill become es-sential. A ll calculations of sam pling error in thispaper should be interpreted as applicable to popu-lations w ith parameters similar to our volunteergroup and are offered solely for rough guidance inplanning studies aimed at more specific measure-m e n t s . In the simplest terms, w e think the use ofvo lunteers is justified in getting started.

Results

Table 1 presents the num ber of personsw ith 24-hr dietary histories covering 2

m onths, 3 months, et cetera. The 10 personsw ho dropped out of the study before provid-

ing at least tw o 24-hr recall reports are ex-cluded. W e w ere successful in obtaining an

i n t e r v i e w i n each of the 11 months contacted

for only 12 people . For71 persons w e w ereable to obtain 8 or more months data. A l-though w e regret not being able to reportmore com plete coverage, w e are generallysatisfied in the light of ourrule that w he ne ve ra subject w as contacted andw as unable orunwilling to be interview ed thatsame day,no f urthe r efforts to i nte rv ie w him w ere madeuntil the fo llow ing calendar month.

Table 2 presents the basic data w ith re-

spect to how variable the 24-hr reports are

w ithin individuals. B ecause those w ith thelargest reported intakes also tend to be more

variable in day-to-day consum ption, the data

are presented as the coeffic ient of variation

Intraindividual variation: median values of the coefficient of variation w ithin individuals (Safter specified number of 24-hr die tary reports

N umber of

Number

subjects

Total

c a l o r i e s

Totalcarbo

h y d r a t eStarch Sugar A nimalprotein

Vegetableprotein

Totalfat

Oleicacid

Linoleicacid

Choles-terol

2345

67

8

91011

90878484

797 3

7 1

502812

0.130.160.160 . 1 7

0.200 . 1 9

0.180.180.210.22

0.160.190.200.200 . 2 2

0 . 2 1

0.230.210.220.20

0.250.280.280.290.290.290.280.270.280 . 2 7

0.270.290.330 . 3 4

0 . 3 2

0.290.310.300.320 . 3 3

0.290.290.320 . 3 4

0 . 3 4

0.340.340.330.380 . 4 3

0.170.230.240 . 2 5

0 . 2 4

0.240.250.270.240.20

0.250.260.260 . 2 7

0 . 2 7

0.260.280.300.320 . 3 3

0.240.260.260.290.270.290.310.300.3003 0

0.240.260.280.290.290.290.280.330.330.36

0 . 3 5

0.400.440 . 4 5

0.440.480.450.500.510.50

0 . 3 5

0 . 3 80.42

0 . 4 2

0.420 . 4 50.450 . 5 1

0.490.46


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30 6 BA LO GH ET A L.

D ata cover at least a 9-month period for 71i n d i v i d u a l s prov iding eight or more 24-hr dietary histories.

(the ratio of the standard deviation among

daily re po rts for an individual to the average

of the daily reports for that individual). Thus ,

a value of 0.20 signifies astandard deviation(w ithin an individual) that is one-fifth as largeas the mean value for that individual. Thedata in Table 2 are the median values for the

entire group under study and show the firs t

2 m onths data for those w ith tw o or morereports, the first 3 months data for those withthree or m ore reports, et cetera. Only triv ialchanges w ould result ifTable 2 w ere to beres tric ted to just those subjects for whom

eight or more reports are available . Table 2

indicates a tendency for larger values of thecoeffic ient of variation to be associated with

additional months of data collection. This

means that for most nutrients tw o or three

monthly reports fairly close together do not

reflect as much variation w ithin the diet as

w ill be observed if additional months of data

are collec ted. Probably this reflec ts both sea-

sonal variation, which w ill be missed if the

data are collec ted w ithin the span of only a

few months, and also the effect of increasing

sample size in reducing the estimation bias

for the coeffic ient of variation. Starch seems

to be leas t affected by a short period of datacollec tion and our es timate of the median

coeffic ient of variation for starch w ithin in-

dividuals w as subsequently little changed

from that derived from only three months

data. On the other hand total fat, o le ic acid,

linoleic acid, and choles terol seem to reflec t

greater variability over the entire study periodthan w as ev ident in the first few m onths. Table2 suggests that unbiased estimates of most die-

tary elements are not likely to be derived

from data collec ted for less than about 6

months (in our study data for 6 months

covered at least a 7-month calendar period),

and for some nutrients almost a whole year

w ould be required. Of course, this, as all

other findings in our study, relates to the

particular subjects w e have studied and may

or m ay not have w ider application. How ever,it w ould seem desirable, before placing m uchre liance on 24-hr die tary data derived en-

tire ly w ithin a few months period, to investi-

gate seasonal variation to determine if it isin fact negligible . Because of these findings,

the remainder of this paper w ill re late only to

those 71 individuals for w hom w e have 8

or more m onths of data co llection. W e havechosen 8 months because of the sharp dropin number of individuals (only 50) for w homw e have 9 or more m onths data, but w e doso w ith full appreciation that our estimatesfor to tal fat, o leic acid, linoleic acid, andcholesterol may be somew hat biased.

Table 3 is based on the 8 to 11 recalls

available for the 71 subjects for w hom w e

have 8 or more months data. It show s both

the median and 90th percentile value of the

coeffic ient of variation within individuals for

each dietary element in our study. Exceptperhaps for total fat, ole ic acid, linoleic acid,

and cholesterol, the coeffic ients of variation

are all reasonable estimates of variability for

these items in our population. Given this de-

gree of variability the re lative s tandard error

of the mean estimated for an individual w ill,

of course , be a function of how many dietary

histories are included in the average. The

relative standard error of the mean is simply

the coefficient of variation divided by the

square root of the number of 24-hr reports.

For example , assuming that daily reports

are random ized throughout the year to elim i-nate or minimize effects of seasonal variation,on the basis of our study population, the

number of daily reports needed to estimate an

individuals die t w ith about 0 .95 probability

of being w ithin 20% of histrue value are

presented in Table 4. The probability and

range of sampling error specified above serve

TA BLE 3

Median and 90 percentile values of S

Totalcalories

Totalcarbo-

hydrateStarch Sugar Animalprotein

Vege-table

protein

Totalfat fat

Oleicacid

Linoleicacid

Choles-terol

Median9 0 t h percentile

0.190.29

0.220.31

0.280.48

0.330.48

0.320 . 5 2

0.250 . 3 6

0.280 . 4 8

0.300.46

0.310 . 5 4

0.480.66

0.440 . 6 7


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RAN DOM REPEAT D I ET AR Y R EC AL LS 30 7

simply to illustrate the number of replicatesrequired at those levels. In order to reachthis level of accuracy for those individuals

reporting more varied diets, it becomesnecessary to obtain more daily reports. Thus,

Table 4 shows the number of replicates

needed to achieve the specified accuracy for

a that half of the population with the leas tvaried die ts, and b 90% of the population,om itting only the 10% with the greatestvariation in day to day consum ption. It isapparent from the table that four reports

spread over the four seasons of the year pro-

vide inadequate precision for classifying in-

dividuals by nutrient intake. Of the nutrientsw e have studied, only total calories , to tal

carbohydrate, and vegetable protein seemreasonably practical for w idespread appli-

cation.

Of course, short cuts are possible and inmeasuring an individuals die t, each indi-

vidual is a separate population, so to speak.

In order to measure saturated fat intake w ith

about 95% probability of lim iting sampling

error to 20% of the mean value for 90% ofthe individuals in a population, it should not

be necessary to collec t 22 24-hr recall inter-view s on everyone. A s Table 4shows, nine

interview s are adequate for that half of the

population eating a less varied die t, and it

should be possible to discontinue data col-

lec tion for such individuals long before ob-taining 22 reports.

Table 5 contrasts the results of our 24-hr

dietary history findings with the data obtainedin the interview about usual dietary intake

that preceded the series of 24-hr recalls. Con-

sidering group averages, it is notew orthy thatnot one of the usual diet averages exceeds

the average derived from 24-hr recalls. In the

case of starch the averages are equal. For all

other nutrients the averages based on 24-hr

recalls are slightly larger.

The corre lation coeffic ients betw een nutri-

ents estimated from usual die t history and

the same nutrients estimated from an averageof 24-hr recalls range from 0.56 for s tarch to

0.83 for oleic acid w ith that for total calories

about midway between these values at 0.69.

Clearly w ith corre lation coeffic ients in thisrange w e are likely to get substantially dif-

ferent results in epidemiologic studies con-

cerned w ith class ifying individuals if we

TA BLE 4

Approximate number of random 24-hr reportsrequired for 20% accuracy of individual mean

N u t r i e n t

A pp r ox im at e n u mb er of r an do mreports required fo r 95% probability

that the sam ple aver age iswithin 20 of t he t ru e i nd iv id ua l m ea n

For half ofpopulation

For 90% ofpopulation

Total c alo rie sTotal c arbo hy drateStarchSugarA nimal proteinVegetable proteinTotal fatSaturated fatOleic acidL in ol ei c a ci d

Cholesterol

4

5

81111

7

89

1023

20

9

1023

232713

23

223044

45

were to use die tary data from one of thesemethods as compared with the other. W hich,

if either, is correct? The simplest and truestansw er is that w e dont know , but w e dothink it is almost an axiom that most peoplemust remember w hat they ate yesterday

better than they can remember w hat they

usually eat.

TABLE 5

Comparison of data from usual die tinterview

w ith the average ofeight or more24-hr dietary reports

Item

G ro up m eans1

Averageof e i g h tUsual

diet o r more24-hrhisto ry dietary

histories

Correlationcoefficient

b e t w e e nu sual diet

a nd a ve ra geof eight ormore 24-hr

reports

T ot al c al or ie s

Total carbohy-drate, g

Starch, g { 176}Sugar, gA nimal protein, gV egetable protein, g

Total fat, gSaturated fat, gO l e i c a c i d , gL i n o l e i c a c i d , g

Choles terol, mg

2 , 3 9 0

33 319 013 5

544173252 615

42 4

2 , 5 7 7

34 419 014 5

6042842830

18

47 0

0.69

0.610.560.610.690.630 . 7 8

0.810 . 8 3

0 . 7 0

0.82

D ata from 7 1 s ub je cts . 1 Expressed inu n i t sof daily consumption. C M ore exactly carbo-hydrate from cereal, rice, potatoes, and legumes.


5/7

30 8 B ALOGH ET A L.

In order to investigate whether our ob-

served corre lations are low simply because

the variables have a large component of

m easurem ent error, w e estim ate the truevalue of the corre lation betw een the variables

measured w ith error according to the fol-

lowing formula rearranged slightly from that

given in 5

where

e X\ eY \= r* 2 i - w w

r = observed correlation coefficient= true corre lation coeffic ient

Ve X = e r r o r variance of X (similarly forY

VX = total variance ofX s i mi la rl y f or Y

The data are as follow s: variance among

individuals for average calorie intake, 320,-500; average variance of the individuals

mean, 32,300; and percentage of varianceamong individuals represented by the aver-

age variance of the individuals mean, 10%.W e have no replicated data for the usual

die t interview in this study and simply as-

sume its error variance is of the same order

as that fo r the 24-hr average and estim ate itat 10% of the total. Carrying out the cal-

culation w e obtain 0.77 (instead of0.69) asthe true corre lation betw een caloric intake

estimated from a history of usual intake and

calo ric intake estim ated as the average of

eight o r m ore 24-hr recall interv iew s.

Discussion

The need for improved die tary measure-

ment techniques to classify individuals for

epidemiologic s tudies has been frequently

stated (1 , 6-8, 20). Because replications of a24-hr die tary recall interview offer some

promise as a practical tool for research in

this area, w e felt it w ould be valuable to de-termine how much daily variation exists as

a guide to the number of replications needed

for estimates w ith a specified range of sam-

pling error. In particular, w e thought itnecessary to introduce a random element in

the selection of the date of interview to

avoid w hatever problems might exist because

the data are serially correlated, or are other-

w ise not randomly distributed even though

w e found one report stating that daily die t

data for individuals can be considered as

independent variables (9). W e w ere also in-

terested in avo iding w hatever special effectsm ight ex ist fo r a day of know n dietaryrecord as opposed to a nonrecord day.

Our data are summarized in the form of

coefficients of variation for an individual.

These data clearly and sim ply present how

much variation there is w ithin an individualin re lation to his own mean value. Unfor-

tunate ly, the authors w hose reports in the

literature w e w ish to use for comparison with

our findings do not present their data in the

f o r m of coeffic ients of variation. Tw o studies

(10, 11) present analysis o f variance tablesfrom which w e were able to calculate pooled

w ithin person sum of squares and, in com-bination w ith additional data reported on

mean values, w ere able to derive coeffic ientsof variation. One study (12) presented the

detailed data for individual subjects and w e

calculated the coeffic ients of variation. The

comparisons are show n inTable 6 . S ix of theseven values w e have for comparison are

reasonably similar to the data in our study.

Considering the range of populations studied,

Israeli m en, Japanese-A merican m en in San

Francisco (10), B ritish cadets (12), and N ewY ork State U niversity staff almost all of

whom w ere w omen (11),it is quite surprisingto find so much agreement. Of course it may

be coincidental and real differences may have

been offset by procedural or sampling dif-ferences. The one statistic not in agreementw ith our ow n is a coeffic ient of variation of

0.07 for daily caloric intake of the U niversitystudy (11). The three other measures w e have

of coefficients of variation for daily caloric

intake within individuals are 0.16, 0 .19 and

0.20, so the 0.07 value is som ew hat of anoutlier and so low as to raise a questionw hether there is not something peculiar in

that population to lead to such uniformity in

daily caloric intake.B ecause of the seem ing consistency in our

data w ith those reported from other popula-

tions it may be satisfactory to use our data,w hich cover a w ider spectrum o f nutrie ntsthan elsew here , for rough planning purposes

prior to obtaining repeat 24-hr recall data

in other populatio ns.

W e w ere able to locate one report in the

literature corre lating the averages of repli-

cated 24-hr recall interviews (3 consecutive


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RAN DOM REPEA T DIETARY RECA LLS 30 9

TA B LE 6

Coefficient of variation of daily dietary intake w ithin indiv iduals (S5/X )

Nutrient

This study Hankin et al. (10) Young et al (ii) Edho lm et al. (12)

Median value amongthose individuals with

eight or more dailyreports

7 -day food reco rdsfor 93 men5

28 -day fo od recordsf or i S a dul ts { 1 76 }

14-day records for1 2 c ad et s1

To tal calorie sTotal c arb oh yd ra teAnimal proteinV egetable pro teinTotal fat

0 . 1 9

0.22

0.320.250 . 2 8

0 . 2 0

0.22

0 25

0 . 3 2

0 . 0 7

0 22

0 . 1 6

P o o l e d v a r i a n c e w i t h i n i n d i v i d u a l s f r o m a n a l y s i s o f v a r i a n c e t a b l e d i v i d e d b y a v e r a g e . 1 Calcuated S,/X d i r e c t l y f r c m d a t a r e p o r t e d .

days) w ith results obtained from an interview

of usual dietary intake (13). A correlationcoefficient of 0.67 for total prote in (the only

nutrient com parable to those in our study)w as quite similar to the 0.69 and 0.63 w eobtained as correlation coefficients for ani-

mal and vegetable prote in, respectively.

How ever, this report did no t agree w ith our

finding that the 24-hr data averaged tohigher levels than the usual die t history.

A special and potentially very valuable useof replicated 24-hr dietary interviews is in

studies in w hich particularly high orders ofprecision are required for individual data.

Epidemiologic s tudies have shown that in-

dividual dietary data and serum cholestero lare very poorly corre lated (14-16). This

seeming contradiction of strong experimental

association betw een die t and cholesterol (17,

18) has been explained by Keys (19) prin-

c ipally on the basis of error inmeasurementof individual die ts. Repeated 24-hr recall

interview s on random dates offer a tool for

controlling the degree of error in individual

dietary intake to a level sufficient to dem on-strate w hether or not corre lation between

specific nutrients and serum cholesterol in-

creases to substantial levels w ith improved

precision in die tary estimates for individuals.

Looking at our ow n data from this view-

point we find that the 62 subjects, for w hom

we have both eight or more 24-hr die tary

recalls and a 1968 serum cholesterol meas-

urement, show correlation coefficients be-tw een serum cholestero l and saturated fatintake as follow s: 1 based on usual diet his-tory, -0.00; 2 based on average of tw o

24-hr reports, -0.00; 3 based on average of

five 24-hr reports, -0.06; and 4) based onaverage of eight 24-hr reports, +0.00.Simi-lar calculations of the corre lation coeffic ient

betw een serum cholesterol and linole ic acid

intake results in -0.09 , -0.11 , - 0.06 and+0.00 for data based on usual diet, tw o 24-hrreports, five 24-hr reports and eight 24-hr

reports, respectively. On thebasis of only 62subjects these values are subject to sub-

stantial sampling error but w e do not seeany ev idence of correlations approachinglarge values w ith increasing precision of

die tary m eas ure me nt.

Our overall conclus ion is that repeated

24-hr recall histories are valuable aids in thedifficult and complex area of classify ing in-div idual dietary intakes and should be usedmore frequently , particularly for those popu-

lations and for those specific nutrients for

w hich the range of variability is not ex treme.

W hen daily variation is extrem e, the m ethodof replicated 24-hr recall interv iew w ill revealthis situation and point tow ard the hard factthat no method short of extensive daily sam-

pling is likely to be successful in accurately

categorizing large numbers of individuals

w ith respect to dietary intake.

Summary

Follow ing an initial interv iew on usualdietary intake, volunteers w ere contacted ona random day each month and given a 24-hrdietary recall interv iew . For 71 subjects dataw ere obtained from eight or m ore monthlyinterv iew s. The variation w ithin indiv iduals


7/7

31 0 B A L O G H E T A L .

is reported for specific nutrients, and nu-trients w ith seasonal variation are identified.The num ber of 24-hr interv iew s required toobtain estimates of individual mean values

within an approximately 20% margin of

sampling error is presented for each nu-

trient. Correlation coeffic ients are reported

betw een the data obtained in the interview ofusual intake and the average of eight or more

24-hr recall interviews..

Corre lation betw een serum cholesterol and

selected nutrients is presented fordietarydata based on usual diet and also the averageof tw o, five , and eight 24-hr reports.fl

References

1. M oJON N IER, L., A N D Y. HA LL. The nationaldiet heart study-assessment ofd i e t a r y ad-h e r e n c e . I. Am . D ietet. Assoc. 5 2 : 2 88 , 1 9 6 8.

2. GROEN, J. J., J. H. M rjuE, H. N . NEUFELD,E. Riss, C . A . B A C H R A C H , F. W . MOUN T A NDH . SM ITh. A n epidemio logic investigation ofhypertension and ischemic heart disease withina defined segment of the adult m a l e populationo f Is ra el . Israeli. M ed. Sci.4: 177 , 1968 .

3. B A L O G H M . J. H . MEDALIE, H . Stnm AN D

J. J. GROEN. The development of a die taryq u e s t i o n n a i r e f o r a n i s c h e m i c heart disease

survey. Israel I . M ed. Sci.4: 195 1968.4. B A L O G H M . J. GROEN, B . Tzua, C . BACHRACH,

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