The relationship between infant mortality rates and medical care and socio-economic variables, Chile 1960-1970.

International Journal of Epidemiology © Oxford Univerjity Press 1979

Vol 8, No 2 Printed in Great Britain

The Relationship between Infant Mortality Rates and Medical Care and Socioeconomic Variables, Chile 1960-1970 MARIE C McCORMICK1, SAM SHAPIRO2 and SUSAN DADAKIS HORN 3

The use of the infant mortality rate (IMR) in this way has several advantages. First, it is based on 2 defined events, birth and death. Secondly, it can be generated on an annual basis. Further, a great deal of research has been directed towards elucidating the circumstances associated with different levels of infant mortality and the associations of IMRs to other types of indicators, both socioeconomic and health services (4—8). In particular, this research would suggest that, in view of the conditions which cause infant deaths (5, 7, 9), IMRs would have applicability as a health status indicator in situations where infectious processes and the problems associated with childbirth, as modified by nutritional status, affect the health of individuals in many age groups. In view of the potential importance of IMR as a health status indicator in developing countries, this study was undertaken with 2 objectives. The first was to ascertain whether or not it was possible to establish the relationships between IMRs with health services (particularly maternal and child health services) and socio-economic factors using routinely collected and published data. The second was to determine the relative effect of health services and socio-economic factors using a multivariate analytic technique. Because data sources were considered available, accessible and relatively complete, Chile, during the decade 1960-1970,

INTRODUCTION

Rational planning for health services requires some assessment of the effect of changes in health services on the health status of a population within a given set of socio-economic circumstances. Indicators of health status adequate for this type of assessment, however, have proven difficult to define and use because of the lack of data specific enough and collected routinely enough for the construction of such measures (1, 2). These difficulties are more pronounced in developing countries, where limited resources and greater health problems require major public decisions as to the best allocation of resources in the face of less adequate data (3). Mortality rates, in particular infant mortality rates, have often been used as the basis for making these necessary decisions in the absence of other welldefined and available health status indicators (1). 1 a J

From the Health Services Research and Development Center and the Departments of Pediatrics and Health Services Administration (Health Care Organization), The Johns Hopkins Medical Institutions, Baltimore, Maryland. Supported by The Community Medical Scholarship Program Grant 5T01 HSOO132 (Bureau of Health Services Research and Evaluation, Health Resources Administration) and the Robert Wood Johnson Foundation Clinical Scholars Program. Presented at the Eighth International Scientific Meeting of the International Epidemiologies! Association, San Juan, Puerto Rico, September 22, 1977.

145

Downloaded from http://ije.oxfordjournals.org/ at RMIT University Library on March 14, 2015

McCormick M C [Health Services Research and Development Center, The Johns Hopkins Medical Institutions, 624 North Broadway, Baltimore, Maryland 21205, USA), Shapiro S and Dadakis Horn S. The relationship between infant mortality rates and medical care and socio-economic variables, Chile 1960—1970. International Journal of Epidemiology 1979 8: 145-154. Infant mortality rates (IMR) have traditionally been considered useful as health status indicators, and changes in these rates are thought to reflect changes in both medical care services and socio-economic circumstances. In order to explore this relationship of IMR with medical care and socio-economic factors in a developing country, Chilean health zone data for the decade 1960—1970 were used to construct 25 variables which were then classified into groups representing antenatal-obstetric services, acute and preventive medical services and socio-economic variables. In an analysis which involved developing a series of linear multiple regression equations for each year of the decade 1960—1970 with IMR as the dependent variable, the percentage of births with professional attention proved to be the strongest variable.

INTERNATIONAL JOURNAL OF EPIDEMIOLOGY

146

was the country and time period selected for the analysis. Since 1952, Chile has provided health services to the majority of its population through a publicly financed national health service (Servicio Nacional de Salud, or SNS). The origins and organization of the SNS have been described elsewhere in great detail (10—14), including the free preventive and curative services provided to pregnant women and all children less than 15 years old (10, 11). The health zones (Figure 1) are the administrative units

PROVINCES

I

Tarapaca Antofagasta

11

Atacaaa Coquinbo

III

Aconcagua

METHODS

IV

Valparaiso

V

Santiago

VI

O'Higgins Colchagua

Publicatians of the Chilean National Health Service, as well as other Chilean government agencies, were searched to provide data for the dependent and independent variables. Where possible, data for each variable for all health zones for each year of the decade 1960—1970 were obtained so that analyses for several points in the time period might be performed to detect any changes which might have occurred. Once the independent variables were defined, stepwise multiple linear regression analysis was used both to examine the strength of the relationship between the dependent variable, the infant mortality rates, and the different independent variables within a set (e.g. all antenatal and obstetrics variables) for each year for which the variables were obtained, and to determine the relative effectiveness of different types of independent variables such as health services vs. socio-economic factors. In each year, the equation which best described the relationship between the dependent and independent variables was selected on the basis of the t-test for the coefficient, and the F-statistic and R2 for the equation.

VII

Curico Talca Haulc Linures

VIII

Nublo

IX

Concepcion Arauco Bio-Bio

X

Malleco Caut in

VI

Valdivia Orsono

XII

Llanquihuc Chiloc Ayscn

XIII

Magallanes

FIGURE 1 Map of Chile showing correspondence between health zones (numbers 1 — 13) and provinces

of the SNS, and, since these zones can be characterized using medical care, census and vital statistics data, they will form the unit of observation for testing the following hypotheses: 1. As the number of facilities and personnel for, or the utilization of, antenatal and obstetrics

RESULTS The dependent variable: infant mortality rates The number of live births according to the province of the residence of the mother and the deaths under one year according to the province of occurrence were obtained for all years except two, 1963 and 1966 (25). The data were used as published, and no correction factors for errors of under-registration


ZONE

services increases, infant mortality will decrease (16, 17). 2. As the number of facilities or personnel for, or utilization of, acute medical services for children increases, the infant mortality rate will decrease (18, 19). 3. As the immunization rates for all available or for a selected subset of vaccines increase, the infant mortality rates will decrease (20, 21). 4. As the volume of nutritional supplement or the available food (measured in calories or grams of protein) increases, infant mortality will decrease (19, 22). 5. As indicators of higher socio-economic status for the population increase, infant mortality will decrease (23, 24). Moreover, since the availability and utilization of health services are not independent of the socioeconomic status of a population, the joint effect of the independent variables would also be examined.

147

INFANT MORTALITY IN CHILE TABLE 1

Antenatal and obstetrical services variables Values with ranges (Zones where value observed) for Chile

Trends within the country

Trends tcross the decade

Years

Crude birtb rate (BR) Number of live births per 1 000 population

All Years (Except 1963, 1966)

I960: 35.0 (21.7/XIII—39.9/II) 1970: 24.5 (20.4/XIII-28.2/IX)

Differences among zones, small.

Decreased

Percent of births with professional attention (PA) Percentage of births with either a doctor or university trained midwife in attendance


1960: 62.3 (30.4/XII-92.6/XIII) 1970: 80.1 (61.4/XII-97.2/XIII)

Highest in mid-region and Magallencs, lower in southern zones

Increased

Midvnves (M) Number of trained midwives per 10 000 population

1969, 1968, 1967, 1965

1965: 8.9 (3.8/VIII—13.4/IV) 1969: 9.3 (2.3/IV-16.8/XIII)

Highest in mid-region and Magallenes, lower in southern zones

Increased, except in Zone IV

TABLE 2

Medical services variables Values with ranges (Zones where value observed) for Chile


Trends across the decade

Variable

Years

Doctors (DR) Number of doctors in (SNS) paediatric service per 10 000 population

1969, 1968, 1967, 1965

1965: 47.4 (17.2/VIII-79.6/V) 1969: 40.9 (19.3/VIII-73.1/V)

Highest in mid-region and Magallenes, lower in southern zones

Increased, except for Zones IV and V Decreased for country

Ambulatory visits (AV) Number of ambulatory visits to (SNS) paediatric health services per 1 000 population


I960: 394.7 (166.5/VIII—541.8/V) 1970: 365.1 (179.0/VIII-469.6/V)

Highest in mid-region in southern zones

Increased in 1969, and then decreased slightly

Total hours of physician care (THR) Number of hours of physician care in (SNS) paediatric health services per 1000 population

1969, 1968, 1967, 1965, 1964

1964: 41.2 (11.7/VIII-69.2/V) 1969: 55.3 (20.4/VIII-92.0/V)

Highest in mid-region, lower in southern zones

Increased

Hospital beds (HB) Number of hospital beds per 1 000 population

1969-1967, 1965, 1964, 1962-1960

1960: 3.84 (1.87/X-5.75/XIII) 1969: 3.52 (2.44/II-5.75/XIII)

Highest in mid-region and Magallenes, lower in southern zones.

Increased in southern zones, decreased slightly in northern and middle zones

of births or deaths were applied, for reasons which are noted below. For the country as a whole, the infant mortality rates decreased over the decade from 132.6 in 1960, to 86.4 in 1969, and rose slightly to 87.1 in 1970. Variations among the zones occurred, however. The highest rates were observed in Zone X, where, in

1960, it was 215.4. Throughout the decade, the highest IMRs occurred in zones VII—XII, and these zones also experienced the greatest decreases, e.g. the IMR for Zone X was 138.6 in 1970. Intermediate values of and intermediate decreases in the mortality rates generally characterized zones I, II and VI, although, by 1970, the rates in Zone I


Variable

148

INTERNATIONAL JOURNAL OF EPIDEMIOLOGY TABLE 3

Variable

Years

Medical services variables Values with ranges (Zones where value observed) for Chile



NUTRITIONAL SUPPLEMENTS: 1960, 1962, 1964

I960: 895.1 (452.6/VI-124.9/XI) 1964: 996.5 (66O.7/X-16O6.3/I)

No clear trends

No clear trends

Kilograms of milk distributed to 'lactantes' (KL) Number of kilograms of skimmed milk distributed to 'lactantes' (children 0 - 2 years by the SNS per 1 000 population).

1967-1969

1965: 334.1 (537.4/IX-77O.3/I) 1969: 361.8 (545.6/XIII-823.0/VIII)

No clear trends

No clear trends

1967-1969, 1964, 1962, 1960

I960: 0.96 (0.44/I-1.84/XII) 1969: 0.97 (0.78/III-1.17/XIII)

No clear trends

No clear trends

IMMUNIZATIONS: Immunization score (IMM) Number of doses of vaccines distributed per 1 000 population adjusted for the number and types of preparations available

TABLE 4

Socio-economic and demographic variables Values with ranges (Zones where vaJue observed) for Chile



Variables

Years

Percent urbamization (U) Percentage of the population in areas defined as urban by Chilean Census

All Years by Extrapolation Between 1960 and 1970 Census

I960: 83.2 (3O.9/XII-92.O/I) 1970: 85.6 (37.9/XII-94.4/V)

Higher in mid-region and Magallenes, lower in southern rones

Increased

Population density (PD) Persons per Km2

All Years

I960: 0.6 (O.6/XIII-137.1/V) 1970: 0.7 (O.7/XIII-2OO.7/V)

Higher in mid-region lower at extremes of country

Increased

Percent

All Years by Extrapolation

1960: 6.9 (6.9/XIII-5O.3/VIII) 1970: 7.7 (5.1/I-48.6/VIII)

Lower in Decreased mid-region and Magallenes, higher in southern provinces

All Years by Extrapolation

I960: 48.7 (39.5/XII-68.1/VI) 1970: 40.4 (33.0/X,XII-57.2/VI)

Not clear, slightly lower in mid-region as compared to southern region

illiterate

(I)

Percentage of population reporting themselves illiterate on the Chilean Census

Percent semi-skilled and unskilled workers (W)

Decreased


Total kilograms milk Distributed (TK) Number of kilograms of skimmed milk distributed by the SNS per 1 000 population

INFANT MORTALITY IN CHILE

were among the lowest. The lowest rates and concomitantly the smallest decreases in levels of infant mortality were concentrated in the central zones HI-V, and in Zone XIII.

1. Antenatal and obstetric services variables (Table 1). Variables obtained to describe antenatal and obstetrical services were: 1) the percentage of live births with professional attention (PA) (25); 2) the number of university-trained midwives per 100 000 population (M) (26); and 3) the crude birth rate (BR) (25). The first variable, PA, increased from 62.3% in 1960 to 80.1% in 1970, with all health zones showing an increase. In zones II and VI—XII, the increase was from a lower range (30-50%) in 1960, to the range 55-75% in 1970; in zones I, III-V and XIII, it was from 65-90% in 1960, but over 90% by 1970 (with the exception of Zone III, where PA was 82.2% in 1970). For the 4 years for which the data were obtained (1965, 1967—1969), M showed a similar pattern, i.e. a general increase in all zones. In contrast, although BR decreased from 35.0 in 1960 to 24.5 in 1970, for the country as a whole, many of the zones showed only small changes. After these variables were placed stepwise into a multiple regression equation with the infant mortality rate as the dependent variable, the equation which best described the relationship of IMR with these variables is IMR = a - b(PA) where a, the equation constant, ranged from 194.456 to 267.477;

b, the coefficient of PA, ranged from 1.1387 to 2.609; F-statistic ranged from 28.860 to 88.902 (statistically significant at p < 0.05 or less for all years); R 2 , or proportion of variance explained by the equation, ranged from 0.699 to 0.888. In all years for which the variable was available, M was eliminated as the weakest variable, and BR second. In all years, the equation in which PA was negatively related to the infant mortality rates, was the strongest equation with highly statistically significant F-statistics, explaining between 70 and 90% of the variance. This indicated that high percentages of births with professional attention were strongly associated with low values of infant mortality rates for all years. 2. Paediatric medical services (Table 2). The variables in this category reflected only paediatric services provided by the National Health Service. Although paediatric services may be obtained outside the SNS system, and SNS services cover children up to age 15 as noted earlier, the vast majority of children receive care in SNS facilities, and these services are concentrated among very young children (28). The independent variables in this set were: doctors in SNS paediatric services (DR) (25) ambulatory visits to SNS paediatric services per 1 000 population (AV) (25), total hours of physician care (inpatient and outpatient) in SNS paediatric services per 1 000 population (THR) (25), and SNS hospital beds per 1 000 population (HB) (29-32). Each of these variables behaved somewhat differently during the decade under study. For THR, there was an increase in value for the country as a whole, as well as for the individual health zones, with higher values being observed in the central zones and lower ones in the more southern zones. This occurred despite the fact that DR decreased slightly over the decade. The number of ambulatory visits (AV) also showed some decline by 1970, but this was after reaching a peak in 1968—69 for most zones. Finally, for both DR and HB, the slight overall national decline masked a small shift of resources from the central zones to the more southern ones which experienced an increase in these rates. When these variables were entered step-wise into a multiple linear regression equation with IMR as the dependent variable for each year of the decade

Detailed equations for all yean may be requested from tbe authors.


Independent variables Four sets of independent variables were developed: the antenatal and obstetric services, paediatric medical services, paediatric preventive services (immunization and nutrition supplement programmes) and socio-economic factors. These variables are summarized in Tables 1 to 4. For each variable, the definition and abbreviation is provided in the first column; the years for which the variable could be obtained, in the second; the value of the variable for the country as a whole for earliest and latest years in which the variable was obtained, with the zones showing the highest and lowest values for each year in parentheses, in the third column; a brief description of the trends among the health zones, in the fourth column; and, in the fifth column, the behaviour of the variable over time from 1960 to 1970.

149

150


where available, the resulting equation was IMR = a - b ! ( A V ) - b 2 ( H B )

3. Paediatric preventive services (Table 3). The data obtained to construct the variables in this group were derived from the activities of the immunization and supplemental nutrition programmes. For both sets of activities, the format in which the data were reported over the decade changed. With respect to the immunization programme, the number of vaccines and the preparations of individual vaccines varied so that they required an adjustment to reflect these changes. In the nutrition supplement programme, reporting the total kilograms of skim milk distributed was changed to reflect the distribution to the various eligible groups (e.g. pregnant and Iactating women). Neither the adjusted immunization score (IMM) (25) nor the kilograms of milk distributed per unit population (KL, KP, TK) (25) demonstrated any

4. Socio-demographic variables (Table 4). The socio-demographic variables which could be obtained were derived from published census data (33, 34). Since the censuses occurred in 1960 and 1970, values of the variables for the intercensal years necessarily represent extrapolations between the 2 values obtained at the ends of the decade. This approach, however, was considered reasonable under the assumption that these were variables which would not be expected to show large yearly deviations from the general trend. The 4 socio-demographic variables were percent of population in urban settings (U), population density (PD), percent of population considered illiterate (I), and percent of those employed who were considered semi-skilled and unskilled workers (W). Both the percentage urbanized and population density increased for the country as a whole and for each zone, but these increases did not alter the basic pattern of a few zones with highly urbanized populations with the remainder being predominantly rural. In contrast, the percentage illiterate and the percentage of employed considered semi- and unskilled workers declined for the country as a whole and for each zone. The variation among the zones, however, was similar with the lowest percentage for these variables (i.e., higher socio-economic status) occurring in the central zones. When these variables were analyzed with the appropriate infant mortality rates, the equation obtained is IMR = a - b , ( U ) + b 2 ( I )


where a, the equation constant, ranged from 170.735 to 222.101; bi.the coefficient for AV, ranged from 0.002 to 0.2976; b 2 , the coefficient for HB, ranged from 2.2575 to 19.1880; F, ranged from 7.0190 to 39.458 (statistically significant at p < 0.05 or less for all years); R 2 , the proportion of variance explained, ranged from 0.443 to 0.864 In other words, lower IMRs were associated with higher rates of ambulatory visits and hospital beds per unit population. The only exceptions to this equation occurred in 1970, when AV was the only variable available; in 1969, when THR entered the equation instead of HB; and, in 1965, when THR replaced AV. In all years for which it was available, DR was the weakest variable, and, with the exceptions already noted, THR the second weakest. The equations involving the paediatric medical services were the only equations in which there appeared a trend with time with respect to the value of the coefficients. Over the course of the decade, the value of the coefficient of HB decreased and that of AV increased, suggesting change in the relative effect from inpatient to outpatient services on infant mortality. The F-values and the RJ (the proportion of variance explained) were somewhat less than those obtained for the antenatal and obstetrics services equations, but both were still high.

clear-cut temporal or geographic trends. There was little consistency in the value of the variables with marked fluctuations for individual health zones from year to year and with respect to other zones. The construction of other variables from these data, such as the vaccine doses per the estimated number of one-year olds for all and individual vaccines or. for a limited number of years, the kilograms of milk distributed per the estimated number of 2 year old children did not result in more stable trends. Not surprisingly, when these variables were introduced into a multiple linear equation, no equation of statistical significance describing the relationship of these variables with the IMR could be obtained for any year except 1967. Since this equation barely achieved statistical significance and was not consistent with the results from other years, it is not presented.


DISCUSSION Feasibility of using published statistics: availability and quality of data In general, the data routinely available in publications of the Chilean government agencies were sufficient to construct variables reflecting most services or factors which might be argued to affect infant mortality, and these data were available for most of the decade 1960—1970. For only 2 years, 1963 and 1966, were there significant enough gaps in the data which could be readily obtained so that analyses could not be performed. That does not mean that data for every variable were available for every year, or, as noted earlier, that the format in which the data were reported did not change.

With 2 exceptions, however, the more important variables were obtained for enough years to assess the stability of the relationships between the dependent variable IMR and the other independent variables. The exceptions reflected the limited data which could be obtained to construct variables relating to available nutrition and socio-economic variables. A major factor affecting both types of variables was the limited number of tabulations available from the 1970 Chilean census. By late 1974, when data collection for this study was being completed, no tables on housing and sanitation, per capita income or available nutrition per capita by province had been published, although such data were available from past censuses. Thus, the socio-economic variables were limited to those used in the analysis, and the only nutritional data reflected the SNS programme for the distribution of supplemental milk. What data were available were used without any corrections or adjustments and assumed to be sufficiently reliable to sustain the analysis on the basis of evidence provided by expert opinion, published analyses, and examination of the data obtained for consistency. This assumption was made with the realization that these uncorrected variables might then be subject to biases. Insofar as possible, evidence for distortions in the variables was sought, but, for the decade under study, the information available was not sufficient to calculate correction factors. What evidence was available (4) (either for earlier or later periods or single years with the decade of study) indicated that errors which occurred did not much alter the relative values of the variables. Instead of estimating corrections based on incomplete data, the variables were calculated from raw data, and the replication of the analyses for several years over the decade was used to assist in the assessment of distortions. Relationship of independent variables to infant mortality In general, the results supported the hypotheses, infant mortality rates were negatively associated with antenatal services personnel and utilization, medical services personnel and utilization and indicators of increasing socio-economic status. The hypotheses not supported were those pertaining to immunization and nutritional status. As noted earlier, the information which could be obtained to describe the latter reflected only the milk distributed through the SNS, and not generally available foods. In Chile, during 1960-1970, the


where a, the equation constant, ranged from 126.828 to 225.060 bi.the coefficient for U, ranged from 0.5087 to 1.3726 bj.the coefficient for I, ranged from 0.1517 to 1.4316 F, ranged from 4.447 to 10.168 (statistically significant at p < 0.05 or less for all years); R J ,the proportion of variance explained, ranged from 0.365 to 0.604. In this equation, IMR is negatively related to percent urbanized and positively related to the percent illiterate, i.e. high IMRs were associated with low urbanization and high illiteracy. Percent semi- and unskilled workers and population density proved to be the weaker variables. While the F-tests achieved statistical significance, they and the R2s were lower than for either of the equations, including the antenatal or including medical services variables. In order to pursue the second goal of the analysis, i.e. to determine the relative effectiveness of the antenatal and obstetric services, medical services and socio-economic variables, the strongest variables from each of the above sets of variables were placed in a single equation with IMR as the dependent variable. These equations, therefore, included PA, AV, THR, I and U. In this scries of equations, PA retained its strong position, and the addition of other variables added little to the variance explained. In part, this result reflected the fact that these relatively strong variables were correlated with each other so that the increment of variance explained over that attributable to PA by the addition of a second variable was that amount of variance which the 2 variables did not have in common.

151

152


that structural variables represent only potential availability of resources, while process variables more clearly reflect actual utilization of resources by a population, and should, therefore, be more closely associated with outcome. (40) The only exception to this was hospital beds per 1 000, and, as was noted earlier, there appeared to be a decrease in the strength of the association of this variable with IMR over the decade. Among the antenatal and obstetrical services variables, PA, the percent of births with professional attention, explained 70 to 90% of the variance in the infant mortality rates. The relatively strong relationship indicated by this finding can be interpreted in two ways: The results might be used to argue the direct impact of the physical presence of a trained professional at the birth event which might be expected to be high in a country such as Chile where, as demonstrated by other studies (5) a high percentage of infant deaths occur in the first few days of life. Additional analyses, not presented here, however, do not show any increased relationship of this variable with neonatal mortality rates as compared to post-neonatal mortality rates. This argues for a broader, more probable interpretation of this variable as an indicator of general accessibility and use of maternal and child health services before, during, and after delivery. In considering this broader interpretation of the percent of births with professional attention, care must be taken to avoid ecological fallacy, i.e. applying the results to a level other than that of this analysis. Thus, for example, if the individual birth were the unit of observation, variables other than the percent of births with professional attention such as birthweight or the presence of major congenital anomalies, might be more closely associated with infant mortality rates. In addition, if the percent of births with professional attention is, indeed, acting as an indicator of accessibility and use of maternal and health services in the Chilean context, then the generalizability of these results to other countries with different organizational arrangements of health services is limited. The relative effect of the independent variable on infant mortality The strength of a single variable, percentage of births with professional attention, also had implications for any equation attempting to evaluate the relative effects of medical care and socioeconomic variables. With one variable capable of accounting for 70 to 90% of the variance, the addition of other variables could not be expected


effectiveness of this programme was questioned because of fluctuations in the availability of imported commodities such as milk due to economic instability (36), by questions about the inappropriate utilization of the milk by the individual family (35), and the value of milk supplements in populations where the prevalence of lactose deficiency may be high (37). These concerns support the observation obtained in this analysis of a lack of relationship between the supplemental milk programme and infant mortality rates, and argue for more direct measurements of available nutrition or nutritional status, especially growth measurements. The lack of relationship between the immunization variable and the infant mortality rates may be attributed to a number of factors. Since the proportion of infant mortality attributed to the common communicable diseases of childhood is relatively small (about 5%) (4), changes in mortality caused by these conditions may be insignificant compared to changes in other, more prevalent causes of death. However, the contribution- of these conditions to the number of deaths attributed to diarrhoeal disease, pneumonia or malnutrition is thought to be more substantial under some conditions than might be indicated by cause of death information (38, 39). Secondly, the way in which the immunization variable was defined, the immunization score, may have served to dampen changes in the number of immunizations per unit population, but other analyses (indicated above and not reported here) provided essentially similar results. Finally, the changes from year to year in the immunization score suggested that the number of doses of a given vaccine distributed in a health zone were not necessarily related to changes in the size of the population or number of births, but reflected immunization campaigns, and this was confirmed, in part, by Dr Behm (36). Although all the variables used to describe the antenatal and obstetrical services and children's medical services were related to the IMRs in the predicted direction, some variables demonstrated stronger associations than others. In particular, such structural variables as doctors in paediatric services and midwives per 10 000 population were weaker than process variables such as ambulatory visits per 1 000 population or percent of births with professional attention. The finding may help to explain the weak associations found between IMRs and medical services in a similar study (23), where only structural variables were available, and is consistent with the theory which indicates


REFERENCES (1) Measurement of Levels of Health. World Health Organization Technical Series, 137, Geneva, 1957. (2) Sullivan D F. Conceptual Problems in Developing an Index of Health. Public Health Services Publication 1000, Series 2 - 1 7 , Washington, DC, 1966. (3) Interrelationships between Health Programmes and Socio-economic Development. World Health Organization Public Health Paper, 49, Geneva. 1973. (4) Behm Rosas H. Mortalidad infantil y nivel de vida. Universidad de Chile, 1962. (5) Puffer R R and Serrano S V. Patterns of Mortality in Childhood. Pan American Health Organization, Scientific Publication 262, 1973. (6) Shapiro S, Schlesinger E R and Nesbitt R E L. Infant, Perinatal, Maternal and Childhood Mortality in the United States. Harvard University Press, Cambridge, Massachusetts. 1968. (7) Mortality in Infancy and Childhood. (United States, ESA/P/WP. 47), 1973. (8) Niswander K R and Gordon M. The Collaborative Perinatal Study of the National Institute of Neurological Diseases and' Stroke. The Women and Their Pregnancies. W B Saunders Company, Philadelphia. 1972. (9) Behar M. Death and disease in infants and toddlers of pre-industrial countries. American Journal of Public Health 54i 1100-1105, 1964. (10) Roemer M I. Medical care in Chile. In Medical Care in Latin America. Pan American Union, Organization of American States, Washington, DC. 1963. (11) Penchansky R. Health services in Chile, May, 1964. In Health Services Administration. Policy Cases and Case Method. Ed. Penchansky R. Harvard University Press, Cambridge, Massachusetts. 1968. (12) Hall T L and Diaz S. Social security and health care patterns in Chile. International Journal of Health Services 1. 362-377, 1971. (13) Viel B. La medicina socializada en Chile. La Medicina' Socialized! y Su Applicacion en Gran Bretana, Union Sovietica y Chile. Universidad de Chile, 1961. (14) Navarro V. What does Chile mean: An analysis of events in the health sector before, during, and after Allende's administration. Health and Society 52i 93, 1974. (15) Estadisticas de Salud, 1970, Servicio Nacional de Salud, Santiago, Chile.

(16) Kessner D M and Kalk C E. Infant death: An analysis by maternal risk and health care. Contrasts in . Health Status, Volume I. Institute of Medicine, National Academy of Sciences, Washington, DC. 1973. (17) Shapiro S, Jacobziner H, Densen P M and Weiner L. Further observations on prematurity and perinatal mortality in a general population and a population of a prepaid group practice medical care plan. American Journal of Public Health 50. 1305—1317, 1960 (18) Ascoli W, Guzman M A, Scrimshaw N S and Gordon J E. Nutrition and infection field study in Guatemalan villages, 1959-1964. IV. Deaths of infants and preschool children. Archives of Environmental Health 15. 439—449, 1967. (19) Scrimshaw N S, Guzman M A, Flores M and Gordon J E. Nutrition and infection field study in Guatemalan villages, 1959—1964. V. Disease incidence among preschool children under natural conditions, with improved diet and with medical and public health services. Archives of Environmental Health 16. 223-234, 1968. (20) Edsall G: Efficacy of Immunization Procedures used in Public Health Practice in the Role of Immunization in Communicable Disease Control. World Health Organization Public Health Paper 8, Geneva, 1961. (21) Ristori C, Boccardo H, Miranda M, Borgono M, Stockebrand S, Canello J, Munoz S, Carrillo B, Concha F, Assael I, Sanchez L, Olivari I, Aravena M, Burton S, and 11 graduates: Vacunacion contra il sarampion con virus vivos de la cepa Edmonston — experience nacional. Revista Cbilena De Pediatria 34. 6 5 6 - 6 6 3 , 1963. (22) Jelliffe D B. Infant Nutrition in the Tropics and Subtropics. World Health Organization Monograph. Series 29, Geneva, 1968. (23) Fraser R D. An international study of health and general systems of financing health care. International Journal of Health Services 3. 369—397, 1973. (24) Ferrero C. Health and levels of living in Latin America. Milbank Memorial Fund Quarterly 43 (4, part 2). 281-295, 1965. (25) Nacimentos, Anuario, Servicio Naciontl de Salud, Direccion General, Departmento Tecnico, for the years 1960-1962, 1964, 1965, 1966-1970. (26) Atenciones, Anuario, Prestadas por el Servicio Nacional de Salud, Servico Nacional de Salud, Direccion General, Departamento Tecnico, Subdepartamento Estadisticas, for the years 1960-62, 1964, 1965, 1969-1970. (27) Crocker D C. Some interpretations of the multiple correlation coefficient. American Statistician 26. 31, 1972. (28) Montoya C. Atencion del Nino. Impreso en los Talleres, del Departamento de Extension Universitaria. (29) Egressos de Hospitalizaciones, Anuario Servicio Nacional de Salud, Direccion General, Departamento Tecnico. Subdepartamento Estadisticas, 1962, 1964, 1965, 1967. (30) Problemas y Actividadcs del Servicio Nacional de Salud in 1960, Servicio Nacional de Salud, Direccion General, 1960. (31) Atenciones Hospitalarias, Servicio Nacional de Salud, Direccion Genera], Subdepartamento de Estadisticas, 1961.


to increase the variance explained by much, despite the evidence of significant contributions when these variables were used in subsets. Furthermore, it was also found that these variables were themselves highly correlated. The effect of such multicolinearity is to create a certain degree of redundancy among the variables which convey essentially the same information (41). The result in this study is that it is difficult to determine the relative effects of health services (by any measure) and socioeconomic factors partially due to the limited number of the latter which were available, but mostly due to the fact that those zones with relatively low IMR tend to have relatively high SE indices and the most favourable measures of medical care.

153

154


(32) Persona] communication, Dr Luis Marchant, Director of Statistics, Servicio NacionaJ de SaJud. (33) III Censas Nacional de Poblacion, Chile, 1960. (34) IV Censas Nacional de Poblacion, Chile, 1970. (35) Undurraga O, Margozzini J and Marin G. Aprovechamiento y conservacion de la leche semidescremada entregada por el Servicio Nacional de Salud a sus beneficiarios. Revista Cbilena De Pediatria 40. 1039, 1969. (36) Personal communication, Dr Hugo Behm Rosas. (37) Paige D M, Bayless T M and Graham G G. Milk programs: Helpful or harmful to Negro children? American Journal of Public Health 62. 1486, 1972.

(38) Ristori C, Boccardo H, Borgono J M and Armijo R. Medical importance of measles in Chile. American Journal of Diseases of Children 1031 66, 1962. (39) Scrimshaw N S, Taylor C E and Gordon J E. Interactions of Nutrition and Infection. World Health Organization Monograph Series 57, Geneva, 1968. (40) Donabedian A. A Guide to Medical Care Administration, Volume III, Medical Care Appraisal — Quality 'and Utilization, pp 2—4. American Public Health Association, Washington, DC. 1969, (41) Gordon R A. Issues in multiple regression. American Journal of Sociology 73. 592, 1968.

(Revised version received 2 January 1979)

The Sixth International Science and Medicine

Conference

on Social

The Sixth International Conference on Social Science and Medicine will be held at the Leeuwenhorst Congress Center, Amsterdam from 5th to 10th August 1979. The three main themes will be: (a) Organisation of health care in their social and political contexts; (b) Decision making in health policy; (c) Intervention strategies in health outcome measures. Preliminary programmes and further information may be obtained from Dr P J M McEwan, Glengarden, Ballater, Aberdeenshire, AB3 5UB, Scotland.

International Symposium on the Protection of Workers against Noise. (Dresden, 27—30 November 1979) This symposium is jointly organised by the Central Institute of Occupational Safety of the German Democratic Republic and the International Labour Office. Further information is obtainable from the International Labour Office, Occupational Safety and Health Branch, CH-1211, Geneva 22, Switzerland.

IXth World Congress on the Prevention of Occupational Accidents and Diseases The Association des Epidemiologistes de Langue Francaise (ADELF) The Association des Epidemiologistes de Langue Franc^aisc (ADELF) will be devoting its 5th Scientific Meeting to growth and development of the child. The meeting will take place in Bruxelles on 4—5 October 1979 and further details can be obtained from

The IXth World Congress on the Prevention of Occupational Accidents and Diseases will be held in Amsterdam (Netherlands) from 6 to 9 May 1980. The central theme of the Congress is — 'Recent developments in the prevention of occupational

risks'. Information may be obtained from:

Professor E A Sand Ecole de Santc Publique ULB Campus Erasme (CP 590) Route de Lennik 808 1070 Bruxelles Belgium

Benelux Organising Committee, IXth World Congress on the Prevention of Occupational Accidents and Diseases, Veiligheidsinstituut, Postbox 5665, 1007 AR Amsterdam, Netherlands.


Meetings

On correlation between SIDS rates and general infant mortality rates.

The relationship between socioeconomic variables and major mental illness in the counties of a midwestern state.

Infant mortality rates and decentralisation in Uganda.

Socioeconomic inequality and its determinants regarding infant mortality in iran.

Relationship between cataract severity and socioeconomic status.

Relationship between death anxiety and demographic variables.

The relationship between war and homicide rates.

Estimating infant mortality rates prospectively in Honduras.

Trends in infant mortality rates in Hungary between 1963 and 2012.

International comparisons of perinatal and infant mortality rates.

Relationship of SOC with sociodemographic variables, mental disorders and mortality.

Relationship between eating rates and obesity.

The relationship between medical law and good medical ethics.

Using electronic health record collected clinical variables to predict medical intensive care unit mortality.

The Relationship between Infant Facial Expressions and Food Acceptance.

Relationship between age, socioeconomic status, and field independence.

The relationship between licensing examination performance and the outcomes of care by international medical school graduates.

Relationship between religious orthodoxy and three personality variables.

Relationship between Statin Utilization and Socioeconomic Deprivation in Hungary.

Relationship between morphological and stabilographic variables in standing horses.

The relationship between sperm viability and DNA fragmentation rates.

What makes infant mortality rates fall in developing countries?

Low-birth-weight effects of demographic and socioeconomic variables and prenatal care in Pima County, Arizona.

Examining the relationship between multiple comorbidities and retention in HIV medical care: a retrospective analysis.