Pediatrics 1990 Popkin 874 82

874 PEDIATRICS Vol. 86 No. 6 December 1990

Breast-feeding and Diarrheal Morbidity

Barry M. Popkin, MS, PhD*; Linda Adair, PhD*; John S. Akin, PhDt;Robert Black, MD, MPHt; John Briscoe, MS, PhD; andWilhelm Flieger, MA, PhD II

From the *Depment of Nutrition and tDepartment of Economics, University of NorthCarolina at Chapel Hill; epartment of International Health, Johns Hopkins University,Baltimore, Maryland; The World Bank, Washington, DC and IlOffice of PopulationStudies, University of San Carlos, Cebu, Philippines

ABSTRACT. This study used a unique longitudinal surveyof more than 3000 mother-infant pairs observed frompregnancy through infancy. The sample is representativeof infants from the Cebu region of the Philippines. Thesequencing of breast-feeding and diarrheal morbidityevents was carefully examined in a longitudinal analysiswhich allowed for the examination of age-specific effectsof feeding patterns. Because the work controlled for awide range of environmental causes of diarrhea, the re-suits can be generalized to other populations with someconfidence. The addition to the breast-milk diet of evenwater, teas, and other nonnutnitive liquids doubled ortripled the likelihood of diarrhea. Supplementation ofbreast-feeding with additional nutritive foods on liquidsfurther increased significantly the risk of diarrhea; mostbenefits of breast-feeding alone on in combination withnutritive foods/liquids became small during the secondhalf of infancy. Benefits of breast-feeding were slightlygreater in urban environments. Pediatrics 1990;86:874-882; breast-feeding, diarrheal morbidity, Philippines.

Diarrhea! disease, a major cause of infant mor-bidity and mortality, is the focus of extensive publichealth program efforts in numerous low-incomecountries. Most recent efforts to alleviate the prob-lems of diarrhea! disease have focused on promotingits case management primarily through the use oforal rehydration therapy. The value of preventivemeasures, such as the promotion of appropriateinfant-feeding practices, has been little empha-sized.1 There has been extensive documentation ofthe protective value of breast-feeding against diar-rhea in settings where poor hygiene is prevalent.

Received for publication Sep 29, 1989; accepted Jan 2, 1990.Reprint requests to (B.M.P.) Carolina Population Center, Uni-versity Square East, CB 8120, University of North Carolina atChapel Hill, Chapel Hill, NC 27516.PEDIATRICS (ISSN 0031 4005). Copyright 1990 by theAmerican Academy of Pediatrics.

Nevertheless, important issues related to the effectsof types of food supplements and the risks associ-ated with their use in different types of environ-ments remain largely unaddressed.

The vast majority of infants who are not exclu-sively breast-fed consume a wide variety of otherfoods, including various milks used as breast-milksubstitutes (commercial formulas and condensedsweetened and evaporated milk), other nutritiveliquids (eg, juices), and gruels, as well as a largenumber of nonnutritive liquids (teas, water,broths). Furthermore, the rapid and often subtleshifts in feeding regimens occurring throughoutinfancy make simplistic definitions of bottle andsupplemental feeding misleading.23 Nonetheless,previous research has generally categorized the in-fant as breast-fed, mixed-fed, or bottle-fed and,therefore, has failed to address the complexity offeeding patterns at any specific time and at differ-ent ages of the infant.4

Effects of a given infant-feeding method almostcertainly vary with the infants age. Not only do aninfants nutritional needs vary at different ages, butso does the infants vulnerability to the harm thatcan result from feeding-pattern changes. Whereasa 3-week-old neonate may suffer from being weanedcompletely from breast milk, a 9-month-old infantmay be minimally affected.

Thus, it must be recognized that a number ofpossible mechanisms exist for the lower frequencyof diarrhea found in breast-feeding infants and thehigher risk observed when other fluids and foodsare introduced. First, breast-fed infants have lessexposure to entenic pathogens transmitted by con-taminated fluids and foods. Second, breast-feedingmay offer protection against diarrhea because ofhumoral and cellular antiinfective properties in hu-man milk. Third, breast milk may promote an

ARTICLES 875

intestinal environment and micnoflora that inhibitsproliferation of entenic pathogens. Finally, breast-feeding can enhance the infants nutritional status,thereby reducing susceptibility to diarrhea.

We present a study of the dynamic relationshipbetween infant-feeding patterns and diarrhea! dis-ease. Data were collected through a longitudinalsurvey in the Philippines, designed specifically tostudy the relationship of diet and health. The se-quencing of breast-feeding and diarrhea! morbidityevents is carefully examined. Longitudinal statis-tical methods allow for the examination of the age-specific effects of different feeding patterns on diar-rheal morbidity. Because the work controls for awide range of environmental causes of diarrhea, theresults can be generalized to other populations withsome confidence.

MATERIALS AND METHODS

Study Design

The study site was metropolitan Cebu, whichincludes the cities of Cebu, Mandaue, and LapuLapu; coastal Cebu towns; a number of villages inmountainous and coastal areas of Cebu; and inhab-ited areas on some smaller islands. We used astratified two-stage sampling procedure to select arandom sample of 33 communities or barangays (17urban and 16 rural).

Households were surveyed to collect data on allbirths between May 1, 1983, and April 30, 1984.Baseline pregnancy surveys were obtained for 3327pregnant women who gave birth during this 12-month period. Ofthese women, 1.1% had stillbirths,0.4% had miscarriages, 0.8% had twin births, 4.6%either migrated before the infants birth or refusedbirth interviews, and 0.7% represented observationswhose data files had faulty information (such asbaseline interview data obtained after birth). Forthis analysis of infant health, the sample consistedinitially of the 3080 women who had single livebirths and for whom baseline and birth informationwere available. An additional 57 women in thesample communities gave birth during the 12-month period but either did not live in the com-munities during pregnancy on were somehow missedduring the screening for pregnant women.

Data on the mothers and infants came frombaseline surveys of the mothers in their sixth orseventh month of pregnancy, from anthropometnicand gestational age information obtained at birthand in the birth information survey, and from ion-gitudinal surveys repeated bimonthly. Communityprice and health facility data came from a set ofhealth personnel, health facility, and food market

surveys. Additional details on the survey design anddata appear eisewhere.57

Variables

Diarrhea! morbidity is represented by a set oftime-varying dichotomous variables that reflect themothers report of whether her infant had an epi-sode of diarrhea in the 7 days before each longitu-dna! survey. This variable is responsive to theindependent variables of interest, was measuredwith a high degree of reliability, occurs with suffi-cient frequency in the sample, and is commonlyused in the literature. The percentages of infantswith diarrhea in the 7 days before each survey were7, 12, 20, 24, 24, and 23 for ages 2, 4, 6, 8, 10, and12 months, respectively. The percentage of studychildren who experienced at least one diarrhea!episode at some point during the first year was 60.3,a number comparable with the rate of 52.9% re-ported for the whole nation of the Philippines for1983.8

Infant feeding data were obtained by trainedinterviewers using survey instruments designed togather precise information on patterns of feedingand food processing. Interobserver reliability stud-ies, preceded by a 2-week dietary data collectiontraining course, were used to ensure high-qualitydata. Additional training and reliability tests wereconducted several times during the survey period.Using food models and measuring aids, trainedinterviewers recorded the frequency of breast-feed-ing and the types, amounts, and feeding frequenciesof all liquids, semisolids, and solids fed to the infanton the day preceding the survey. Information wasalso obtained on the frequency of breast-feedingand whether infants were given foods in specifiedcategories (eg, water, breast milk substitutes, semi-solid or solid foods, etc) 7 days before each survey.

For this analysis, infants were grouped into a setof mutually exclusive feeding categories, reflectingbreast-feeding and consumption of other foods andliquids. An infant was considered to be exclusivelybreast-fed if its entire intake consisted only ofbreast milk from its own mother. This definitionexcluded consumption of any foods or liquids thatcould potentially introduce pathogens to the infant.A second category included breast-feeding in corn-bination with nonnutnitive liquids such as waterand herbal teas. More than 95% of the infants inthis category were fed water. A third category en-compassed breast-feeding in combination with nu-tritive liquids (eg, juices, milks) or foods (sernisolidsor solids). The fourth category represented nobreast-feeding at all.

In Table 1 we present the prevalence of infant-

876 BREAST-FEEDING AND DIARRHEAL MORBIDITY

TABLE 1. Breast-feeding Patterns During Infancy, Metropolitanpines, 1983_1985*

Cebu Area, Philip-

Infants by Ageand Residence

Bre ast-feeding Patterns.

Breast Milk.

Breast Milk +. -

Breast Milk + Nutritive No Breast nOnly Nonnutritive foods,t Maybe Nonnu- Milk

Liquids Only tnitive Liquids

2 moRural 53.3 17.3 23.1 6.3 698Urban 24.0 19.4 38.0 18.7 2186Both 31.1 18.9 34.4 15.7 2886






* Based on feeding behavior on the day preceding the survey. Horizontal columns total

100%.t Nutritive liquids including other milks or semisolid and solid foods.

feeding patterns for urban and rural infants frombirth to 12 months. Urban and rural patterns wereexamined separately because previous analyses ofthe Cebu data have found important differences inhealth-related behaviors and their determinants be-tween these samples, justifying their separate con-sideration.67 Even though many continued tobreast-feed, infants were introduced to other foodsand liquids, particularly nonnutritive ones, veryearly. At 2 months, approximately 19% of infantswere fed breast milk in combination with nonnu-tnitive liquids and 34% were fed breast milk andnutritive foods or liquids (possibly in combinationwith nonnutnitive liquids). Expressed in anotherway, approximately 63% of breast-fed infants hadtheir diets supplemented with some other liquid orfood by the age of 2 months. By 8 months essen-tia!ly all breast-fed infants were receiving otherliquids and foods.

We note several points related to the measure-rnent of breast-feeding in this study. First, mothersmay move in and out of exclusive breast-feeding.They may exclusively breast-feed their infants atone age, add foods at a later age, and then, evenlater, return to exclusive breast-feeding. For ex-ample, 116 urban (5.3%) and 25 rural infants (3.6%)

made transitions from more complex feeding pat-terns at 2 months back to exclusive breast-feedingat 4 months (Bisgrove EZ, Popkin BM, Barba C.,1988. Unpublished manuscript). Most infants re-ceived teas, water, and other nonnutnitive broths,or some gruels, juices, or other foods or liquids withnutritional value at an early age. However, manyinfants received these non-breast-milk items onlyon a sporadic basis, and in those cases the con-sumption is not likely to have a long-term effect oninfant morbidity.

Second, some infants were fed by a wet nurse. Ateach 2-month interval, 2% to 4% of the infantswere nursed at least once in the day preceding thesurvey by a woman other than their mother. In nocase in the data, however, did an infant receivebreast milk from a wet nurse without also receivingbreast milk four or more times that day from itsown mother. The possible effects of wet nursing arenot considered in this study. Third, most breast-feeding is initiated in the third to fifth day afterbirth. Before this, the liquids fed to newborns areboiled, and no effect on neonatal health seems toresult from their consumption; thus prelacteal feed-ing is not considered in the definition of feedingpatterns.9

ARTICLES 877

Statistical Controls

To understand the precise relationship betweenfeeding and infant morbidity, it is necessary tocontrol for various biologic and behavioral variablesthat affect susceptibility to illness and exposure topathogens. We used longitudinal multivariatemethods designed for analysis of behaviors in hu-man populations. These methods are appropriatein cases where either it is not possible (for ethicaland financial reasons) to conduct experimentalstudies, or the research must be conducted in nat-ural settings to observe behaviors in a realisticcontext. These methods allow for the evaluation ofa number of important susceptibility and exposurefactors considered to be significantly related todiarrhea during the first year of the infants life.Susceptibility variables capture information aboutthe infants biologic endowments, including healthstatus at birth (measured by gestational age andbirth weight) and subsequent healthiness (meas-ured by weight velocity and weight velocity inter-acted with weight). Sex of the infant is an exoge-nous variable that may represent susceptibility dif-ferences because of genetic endowments of theinfant or the effects of different health-related be-haviors of the mother when dealing with males vsfemales.

Exposure variables reflect an infants chances ofcoming into contact with pathogens. These includemeasures of personal hygiene (use of soap), waterquality, excreta disposal practices, food hygiene,and the mothers concern with preventive measures(evidenced by use of preventive health care). Diar-rhea tends to follow distinct seasonal patterns as aresult of varying exposures to the contaminatedenvironment. In this case study, seasonality wasrepresented by a measure of rainfall in the 14 daysbefore each survey because this varies more season-ally than temperature or other variables. Othercontrol variables represent crowding in the corn-munity or within the household, either of whichmay affect the probability of person-to-person con-tacts, and the resultant transmission of pathogens.The presence of animals (chickens, livestock, pets)in or under the house also represents exposure toadditional pathogens that can be transmitted fromanimals to humans.

Modeling Methods

The model presents the probability that an infantwill have diarrhea as the result of feeding practicesand of the full set of susceptibility and controlvariables described above. To understand the pre-cise total effect of breast-feeding on diarrhea, whenit is and is not combined with various other foods,

a number of relationships must be considered. Theanalysis of the relationships in this study was basedon a coherent behavioral and biomedical model,discussed in detail elsewhere.#{176} In general the modeldisaggregates a set of health-affecting processesinto a series of logical relationships, beginning witha set of community and household socioeconomicconditions and progressing through their effects ona set of intermediate behavioral and biologic van-ables (eg, food processing and birth weight) tohealth outcomes.

Inasmuch as breast-feeding may not only directlyreduce the incidence of diarrhea, but also increasethe infants nutritional status, in turn reducing theseverity and incidence of diarrhea,3 these mdi-rect effects must also be considered. Prior growthvelocity (grams per day during each measurementperiod) and growth velocity interacted with priornutritional status (the interaction term is includedbecause a given growth velocity may have differenteffects on health according to the childs nutritionalstatus when the growth began) are included in thediarrhea analysis to capture the indirect nutritionaleffect of breast-feeding on diarrhea! morbidity. Itis also possible that exclusive breast-feeding couldhave direct and indirect effects in opposite direc-tions, particularly at older ages when exclusivebreast-feeding may be associated with growth fal-tering.

The procedure we used for estimation of thediarrhea model is a longitudinal probit. This mu!-tivariate procedure allowed us to calculate the neteffect of each independent variable in the model onthe probability of diarrhea can be accounted for.Because it is a longitudinal model, the timing andsequencing of the biologic and behavioral processesaffecting each diarrhea can be accounted for. Forexample, infant feeding is recorded and modeledfor a time period just before the observation of thepresence or absence of diarrhea. The other biologicand behavioral controls also are modeled with con-sideration of the likely timing of their effects (CebuStudy Team. 1989. Unpublished manuscript).10

The longitudinal probit procedure also accountsfor several normally encountered statistical prob-lems, in particular the endogenity of certain behav-ions and outcomes (mothers may recognize threatsto their infants health and take measures to reducethem), and the effects of correlation of unobservedfactors over time, (Cebu Study Team. 1989. Unpub-lished manuscript).15

RESULTS

Results are derived from the model representedin detail in the Appendix. The coefficients are

U Only breast milkD Breast milk + nonnutritive liquidsU Breast milk + nutritive foods I liquidsri No breast milk

Adjustedprobability

of 20having

diarrhea

.10

4 6 8 10Age (in months)

. Only breast milk Breast milk + nonnutritive liquidsD Breast milk + nutritive foods I liquidsLI No breast milk

2 4 6 8Age (in months)

Fig 1. Breast-feeding and diarrhea! morbidity, Cebu,Philippines, 1983 to 1985: urban sample.

10 12


maximum likelihood estimates of the effect of eachvariable on the probability of having diarrhea. Anegative coefficient means that the probability isreduced by that variable, with the T statistic mdi-cating the statistical significance of the effect.

Diarrhea was strongly affected by mode of feed-ing. For both the urban and rural samples, exclusivebreast-feeding (no other liquids or foods given) 7days before a survey significantly decreased theprobability that an infant would have diarrhea dun-ing the week from that date to the survey date.Similarly, infants fed breast milk in combinationwith nonnutnitive liquids 7 days before a surveyhad decreased probability of diarrhea, relative toall except fully breast-fed infants. Infants fedbreast-milk in combination with nutritive foodsand/or liquids, however, were not found to be sig-nificant!y less likely to have diarrhea than infantswho were not breast-fed. The combined impact ofthe three breast-feeding variables is statisticallysignificant for the urban and rural samples.

In Figs 1 and 2 we present information on theresponsiveness of diarrhea to changes in breast-feeding for the urban and rural samples. The esti-mated relationships reflect the direct effect ofbreast-feeding on diarrhea and the indirect effectsof breast-feeding on growth and, in turn, of growthon diarrhea. If each infant has a!! other character-istics controlled so that only the infant-feedingpattern varies, the prevalence of diarrheal morbid-ity associated with each feeding pattern is pre-sented. In other words, these figures represent theadjusted diarrhea! morbidity probabilities.

Exclusively breast-fed infants tended to have alow likelihood of developing diarrhea; the likelihoodfor infants fed both breast milk and nonnutritiveliquids was higher. Diarrhea! morbidity was in-creased even more for infants fed breast milk plusnutritive foods or liquids, and the highest probabil-

Adjustedprobability

ofhaving

diarrhea

Fig 2. Breast-feeding and diarrheal morbidity, Cebu,Philippines, 1983 to 1985: rural sample.

ity of diarrhea was found in infants who were notbreast-fed at all. Between one fifth and one thirdof all infants who were not breast-fed 7 days beforea survey can be expected to have diarrhea in the 7days between that date and the survey day.

The relative risks of diarrhea! morbidity for in-fants who were not exclusively breast-fed, pre-sented in comparisons with infants who were exclu-sively breast-fed, appear in Table 2. From thoseresults, it can be seen that the feeding of nonnutri-tive liquids had important effects on diarrhea! mor-bidity. Depending on age, the infant was 2.0 to 3.2times as likely to have diarrhea if nonnutritiveliquids were fed in addition to breast milk than ifhe or she was only fed breast milk. When nutritivefoods and/or liquids were added to the breast milkdiet, the infant became 4.7 to 13.1 times as likelyto have diarrhea! morbidity. At given times duringthe first 6 months, the infant who was not breast-fed was from 4.7 to 16.8 times as likely to havediarrhea as was the exclusively breast-fed infant.

By 8 months of age, when all breast-feedinginfants in the sample were fed a mixed diet of breastmilk and other nutritive foods and liquids, therelative benefits of breast-feeding fell considerably.Only in urban areas was the probability of diarrheafor breast-fed infants at this age lower than it wasfor infants who were not breast-fed and, even there,the difference was small. The results indicate aclear inverse relationship between age and the pro-tective effects of breast-feeding on diarrheal mor-bidity.

DISCUSSION

The Cebu, Philippines, case study reaffirms thegeneral finding of a large body of research thatbreast-feeding protects against diarrhea! morbid-ity.4 In particular, the results indicate that addingeither nonnutritive liquids or nutritive foods or

ARTICLES 879

TABLE 2. Adjusted Relative Risk and 95% Confidence IntervFeeding Patterns, Metropolitan Cebu, Philippines, 1983_1985*

a! of Diarrhea! Morbidity by Childs Age and Infant-

Infants by Age and Breast Milk Breast Milk + Nonnutni-. - - .

Residencet Only tive Liquids

Relative 95% CI

Breast Milk + Nutritive.

Foods/Solids-

No Breast Milk

Relative 95% CI Relative 95% CIRisk Lower Upper Risk Lower Upper

Risk Lower UpperLimit Limit Limit Limit Limit Limit

Age group: 2-6 moUrban sample

2 mo 1.00 3.17 2.50 3.83 13.30 6.15 20.44 17.32 6.74 27.894 mo 1.00 2.12 1.77 2.46 12.93 6.04 19.81 13.72 6.14 21.306 mo 1.00 3.18 2.53 3.84 10.61 4.63 16.60 13.45 5.24 21.66

Rural sample2 mo 1.00 2.24 2.01 2.47 5.67 4.31 7.03 5.68 4.31 7.054 mo 1.00 1.97 1.80 2.13 6.30 4.93 7.66 5.64 4.52 6.766 mo 1.00 2.21 2.07 2.35 4.73 3.95 5.52 4.73 3.97 5.49

Age group: 8-12 moUrban sample

8 mo 1.00 1.32 1.22 1.42lOmo 1.00 1.32 1.23 1.4212 mo 1.00 1.32 1.23 1.42

Rural sample8 mo 1.00 1.02 1.02 1.03

10 mo 1.00 1.03 1.02 1.0312 mo 1.00 1.04 1.03 1.04

* The relative risk reported here is the mean of individual-level risks, each of which is the ratio of individualprobabilities. The individual-level probabilities are estimated as in Figs. 1 and 2. The standard deviation of theindividual re!ative risk is multiplied by 1.96 and the product is added and subtracted to the mean relative risk to obtainthe 95% confidence interval (CI).t The relative risk is the ratio of the risk of diarrheal morbidity or respiratory infection for infants in each age-feedingcategory compared with exclusively breast-fed infants for 2 to 6 months and for those breast-fed plus fed nutritivefoods and liquids for ages 8 to 12 months. Risks are adjusted for a set of exposure and susceptibility factors mentionedin the text.

liquids to the breast-milk diet is associated with alarge increase in the occurrence of diarrhea andthat the protective effect of breast-feeding de-creases with age. It is important to note that if theclassification procedure used in this study causesinfants to be placed into a breast-feeding categoryto which they do not continuously belong, thatcategory is likely to be either the only-breast-milkor breast-milk-plus-nonnutnitive-liquids category,because both represent feeding patterns that forshort lengths of time occur periodically, probablybecause of such factors as illness or shortage offoods. If the assertion is correct, we are creating aconservative test of the hypotheses about the posi-tive health effects of breast-feeding. Benefits ofbreast-feeding would be underestimated becausesome infants who are classified as being exclusivelybreast-fed actually periodically receive other liquidsor foods, and some infants classified as breast-fedwith the addition of only nonnutnitive liquids ac-tually periodically receive nutritive liquids or foods.

A major conclusion based on the case study is ofthe benefit, during the first 6 months of life, ofexclusive breast-feeding relative to being fed breastmilk and nonnutritive liquids such as water, teas,and herbal broths. Consumpion of these nonnutni-

tive liquids seems to have a large adverse effect ondiarrhea! morbidity. The results also suggest thatearlier research that misclassified infants fed non-nutritive liquids as being exclusively breast-fedprobably reported a smaller protective effect ofexclusive breast-feeding than actually existed in thesamples analysed. The relationship found in theCebu study is statistically strong and large in mag-nitude, and it holds true when a wide range ofexposure and susceptibility factors are controlledin the analysis. Eliminating nonnutnitive liquidsfrom the infants diet should pose no health risksunder most climatic conditions because infants canmaintain adequate hydration status while exclu-sively breast-feeding even in warm climates6 andcould be expected to substantially reduce diarrheain this age group.

This study also indicates that supplementationof breast-feeding with nutritive foods or liquidsfurther increases the risk of diarrhea above thatwhich results when only nonnutnitive liquids areadded to the breast-milk diet. As a consequence, itcan be inferred that it is important to promoteexclusive breast-feeding up to the age at which thebreast-fed infant requires complementary foods topromote adequate growth and development. The


dilemma created because the weanling is protectedfrom diarrhea by delaying supplementation, butneeds relatively early supplementation for adequategrowth, leads to a certain ambiguity in this age-of-supplementation recommendation. The need forsupplemental foods almost certainly occurs before5 to 6 months of age but could come as early as 3to 4 months.

The benefits of receiving breast milk alone or incombination with other foods or nutritive liquidsbecome significantly smaller during the second halfof infancy. At these later ages when the infantsimmunologic system is more mature, the quantita-tive effect of passive immune factors is diminished,and essentially all infants are exposed to pathogensin the diet, so the benefits of breast-feeding as aprotection against diarrhea become relatively small.

Because of the extensive controls for other envi-ronmental and seasonal exposure and susceptibilityvariables used in this empirical study, the resultscan be taken to indicate that exclusive breast-feeding will be associated with reduced diarrhea!morbidity in a wide range of environments. Thestudy has used more precise categorizations of in-fant feeding than past work related to diarrhea, hasconsidered carefully the sequencing of feeding anddiarrhea! morbidity, and has controlled for a corn-plete set of confounding variables. That the esti-mated impacts of breast-feeding in diarrhea reduc-tion are so robust, given the statistical care taken,is strong evidence of the positive value of breast-feeding on infant health.

The case study has found differences in the pro-tective effects of breast-feeding in urban and ruralenvironments. Infants in urban areas appear toreceive a slightly greater benefit from exclusivebreast-feeding. This may reflect a greater probabil-ity of exposure to diarrhea! pathogens in the urbanenvironment, perhaps through some pathway leftunmeasured in this study. Urban infants in thePhilippine sample are exposed to a more crowdedenvironment with poorer excreta disposal practices.Water quality, which generally is better in ruralareas, seems to have a smaller effect on diarrhea(Cebu Study Team. 1989. Unpublished manu-script)0 than excreta disposal practices. In general,studies based in low-income countries where theinfant is exposed to high levels of pathogens have

estimated a greater benefit from breast-feedingthan have studies from less contaminated environ-ments.

It has been estimated elsewhere that the effectiveglobal promotion of breast-feeding could reducediarrhea! morbidity rates 8% to 20% for infants upto the age of 6 months. Using 1982 estimates ofglobal diarrhea! morbidity rates of 2.3 episodes penyear for this age group, and an estimated 1988global population size of 70.7 million infants, theseauthors estimated that 6.5 to 16.3 million episodesof diarrhea! illness per year could be averted world-wide. Although these calculations are only crudeestimates, they show the magnitude of what mightbe achieved through even modestly positive resultsfrom the promotion ofbreast-feeding. While breast-feeding promotion, particularly the encouragementof exclusive breast-feeding, will reduce only a por-tion of the worlds episodes of diarrhea, it willalmost certainly reduce the risk of diarrhea duringthe age at which infant growth is most rapid and inwhich weanling diarrhea is believed to pose thegreatest threat to survival.

ACKNOWLEDGMENTSThis article is part of a collaborative research project

involving the Office of Population Studies, University ofSan Carlos, Cebu, Philippines, directed by Dr WilhelmFlieger; the Nutrition Center of the Philippines, directedby Dr Florentino S. Solon; and a group from the CarolinaPopulation Center, University of North Carolina atChapel Hill (UNC-CH). Barry M. Popkin of the UNC-CH is the project coordinator. Funding for parts of theproject design, data collection, and computerization wasprovided by the National Institutes of Health (ContractsR01-HD19983A, R01-HD23137, and R01-HD18880), theNestles Coordinating Center for Nutrition Research,Wyeth International, the Ford Foundation, the US Na-tional Academy of Sciences, the Carolina PopulationCenter, UNICEF, the US Agency for International De-ve!opment, and The World Bank. Funds for data analysesfor this study were provided by the National Institutesof Health (R01-HD19983A) and the Office of Evalua-tions, UNICEF.

We acknowledge the support, advice, and encourage-ment of the UNICEF staff, including Kathleen Cravero,Peter Greaves, Julian Lambert, Roger Pearson, and par-ticularly, Samir Basta and Margaret Kyenkya. DavidFugate, Debora Barnes, Frances Dancy, and EmelitaWong provided invaluable assistance. We thank DavidGuilkey for his central role in developing the model andstatistical estimation techniques.

APPENDIX

Longitudinal Analysis: Structural Equation for Diarrhea Incidence in Week Preceding Survey by Urban-RuralResidence in Metropolitan Cebu, 19831985*

Explanatory Variables Urban Rural

Coefficient T Statistics Coefficient T Statistics

EndogenousSusceptibility

Lagged weight velocity (g) -7.57 x i0 -1.19 -7.33 X i0 -0.64Lagged weight velocity inter- 2.65 x 106 2.18 2.08 X 106 0.91

acted with weight (g x g/d)Gestational age (wk) 0.12 2.98 -0.03 -0.64Gestational age interacted with 9.32 x 106 1.62 -6.30 x iO -0.06

age (wk x d)Susceptibility/exposure

Feeding practicesExclusive breast-feeding 1.39 -4.87 -0.87 -2.49

(prob)Breast-feeding with nonnutni- -0.91 -3.20 -0.50 -1.32

tive liquids (prob)Breast-feeding with nutritive -0.17 -1.13 -8.88 X iO -0.01

foods and liquids (prob)Total calories (cal) -3.35 x iO -1.40 3.42 x i0 0.79Health service use: preventive -0.23 -1.25 0.44 1.65t

health careExposure

Personal and environmentalhealth practice

Good quality water source -0.30 -3.20 -0.23 -1.31(prob)

Soap purchases/capita/week -4.43 x iO -0.07 -1.27 X iO -0.95(g)

Pathogenic food processing 0.82 1.69t 0.20 0.43(prob)

ExposurePersonal and environmental

health practicePoor excreta disposal (pnob) 0.80 4.85 0.45 2.08Poor excreta disposal inter- -1.24 X iO -1.94t -1.58 X iO -1.93t

acted with age (prob x d)Exogenous

SusceptibilityChilds age (d) 1.28 x i0 2.25 2.05 x iO 1.96Childs sex (0-1) -0.04 -0.49 -0.11 -0.78Childs sex interacted with age 6.26 x iO 2.31 5.23 x iO 1.01

(0-1 x d)Exposure

Animals in house (0-1) -3.95 x i0 -0.09 0.06 0.72Animals under house (0-1) -0.01 -0.44 -0.02 -0.22Baby crawling interacted with 0.04 0.77 0.02 0.22

animals in house (0-1)Crowding

No. of preschoolers (0-6) -0.04 -2.31 0.02 0.79No. of people/room (0-9.5) 0.01 1.10 1.42 x iO 0.08Community density (people/ 6.20 x 106 6.80 4.62 x 10_6 2.86

km2)Cumulative rainfall in last 2 wk 7.13 x iO 0.16 1.83 x i0 2.73

before survey (in)Cumulative rainfall interacted 1.45 x 106 0.81 -3.25 X iO -1.26

with age (in x d)Others

Constant -6.01 -3.67 -0.55 -0.30p 0.11 6.86 0.15 4.42Log likelihood ratio -5294.7 -1609.9

* The units for the explanatory variables are in parentheses. Prob is the predicted probability of the explanatoryvariable. The significance levels for testing whether the coefficient is zero is indicated by t for 10%, 1 for 5%, and for 1%.

ARTICLES 881


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FAMILY (PRIMARY CARE?) DOCTORS LOSE FAVOR - WHEN IT PAYS

The popular labor-relations image at a time of exploding medical expenses isthat of employers trying to shift costs to workers, who in turn fight to keep asmany benefits as possible. But a new study by National Research Corp., ahealth-care research firm in Lincoln, Neb., suggests that many employees maybe more flexible than previously thought.

In a nationwide survey of 1,000 adults, National Research found 41% wouldbe willing to choose a doctor from a list approved by their employer in exchangefor a lower insurance premium. Thats up from 28% just two years ago. Inresponse to a similar question, 32% said they would be willing to select aphysician from a list supplied by a hospital if they could save 10% on the costof an office visit.

Health costs are starting to hit peoples pocketbooks, says. . .a senior vicepresident at National Research. Their premiums and deductibles are goingup. While many patients still take a money-is-no-object attitude towardspecialists or surgeons, she says, they are growing more receptive to savingmoney at the general-practitioner level.

In effect, . . .theyre telling their family doctors, Youre good, but youre notthat good.

Ruffenach G. Family doctors lose favor - when it pays. The Wall Street Journal. January 2, 1990.Health Costs.

Documents

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