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Vitamin A deficiency in children aged 6 to 24 months in S~ao Paulo State, Brazil
Nutrition Research,Vol.20, No. 6, pp. 757-768,2000 Copyright0 2000Elsevier Science Inc. Printed in the USA. All rights reserved 027 1-53 17/OO/$-seefront matter ELSEVIER
VITAMIN A DEFICIENCY
PII: SO271-5317(00)00177-9
IN CHILDREN AGED 6 TO 24 MONTHS IN SAO PAUL0 STATE, BRAZIL
IS Ferraz, M.D. ‘*, JC Daneluzzi, Ph.D. I, H Vannucchi, Ph.D.2 1 Department of Child Care and Pediatrics, Faculty of Medicine of Ribeirgo Preto, University of Sb Paulo. 2 Department of Internal Medicine - Division of Clinical Nutrology, Faculty of Medicine of Ribeirgo Preto, University of Sb Paulo. ABSTRACT Vitamin A deficiency (VAD), mainly the subclinical form, is endemic in several areas of the Brazilian Northeast. However, studies concerning its prevalence and etiology (risk factors) in urban areas of Sgo Paul0 State are lacking. The objective of the present study was to identify VAD and the risk factors among children attending a Child Care outpatient clinic in Ribeirso Preto city, Szo Paul0 State, Brazil. A total of 103 children aged 6 to 24 months without any diarrhea or fever illness were selected from a pediatric outpatient clinic. A careful clinical history and physical examination provided information about breast-feeding, parental education, family income, family size, birth weight and anthropometric data. The children also underwent ophthalmologic examination to check for signs of xerophthalmia and were submitted to blood tests in order to determine hemoglobin and serum iron, zinc and retinol levels. Serum retinol levels E 0.70 pmol/l are considered to be deficient by the World Health Organization. Retinol levels, determined by high performance liquid chromatography (HPLC), were E? 0.70 p?mol/l in 22 children (21.4%). No child had xerophthalmia. The overall mean serum zinc level was 108.9 pg% (2SD + 43.1 pg%) and the values for children with and without VAD were 105.1 pg% (2SD + 44.1 pg%) and 110.0 pg% (2SD + 43.2 pg%) respectively, with no child presenting serum zinc levels below the normal range. None of them showed a
Breast-feeding,
Child, Zinc.
I* Corresponding Author: Faculty of Medicine of RibeirZo Preto, Department of Child Care and Pediatrics, University of S5o Paula, Av. Bandeirantes, 3900. 14049-900. Ribeirgo Preto, SP, Brazil. Telephone and FAX number: 16-633-0136
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INTRODUCTION Although the deleterious effect of vitamin A deficiency on the organism have been known since the first quarter of the present century (l), vitamin A deficiency (VAD) continues to be a public health problem in several parts of the world especially in developing countries (2). Although it considers VAD to be of low magnitude on the American continent, the WHO (3) has pointed out some high-risk areas for VAD such as Haiti and some regions of Brazil. In Brazil, xerophthahnia was first described in the past century in slave children aged 1 to 7 years living in Rio de Janeiro (4). Although VAD is known to occur in the Northeast region of Brazil (4), considered to be the region most economically underprivileged in the country, scarce reports of the occurrence of VAD have been recently published concerning the Southeast region (5, 6), considered to be the richest in the country, the State of Sb Paul0 in particular. In view of the various functions of vitamin A in the organism - improved immune function with reduced susceptibility to infections (7) - and the consequences of its deficiency in the organism - increased risk of morbidity and mortality in populations at risk (8-11) -, in addition to reports of improved childhood morbidity and mortality rates in places where this problem has been fought, (12, 13), the importance of studying VAD is clear, especially in a locality where children present high morbidity rates due to respiratory and diarrheic diseases and where infant mortality still reaches worrisome rates (25/1,000 liveborns’). In addition, the search for eventual risk factors may help plan strategies to combat this nutritional deficiency. Several risk factors for VAD exist (3): protein-energy malnutrition (PEM), low prevalence of breast-feeding, low consumption and low availability of foods rich in vitamin A, low income with consequent precarious living conditions, high prevalence of low birth weight, low educational level of the parents, high prevalence of febrile and parasitic diseases, and precarious basic sanitation conditions. Furthermore, serum zinc levels can also interfere with serum vitamin A levels (14) since this trace element participates in the synthesis of retinol binding protein @BP) (15, 16). In addition, due to its adequate content of vitamin A and of “anti-infectious” components, human milk seems to protect infants against the development of VAD and of its consequences (4, 17-20), especially during the first six years of life (3). The objective of the present study was to determine the presence of VAD among children considered to be healthy aged 6 to 24 months, living in an urban area of the town of de Rib&b Preto (Sb Paulo), regularly followed up at a Puericulture outpatient clinic with the assistance of the local university. Some of the probable risk factors for the development of this deficiency in the community were also investigated.
SUBJECTS Subiect recruitment: A total of 103 children aged 6 to 24 months regularly followed at the unit and presenting no acute episodes of fever and/or diarrhea - regardless of a previous history of morbidity - were included in the study, which lasted corn June 1997 to March 1998. The children were divided into four groups according to age range: the first group (27 children), 6 months of age (k 10 days); the second group (25 children), 12 months of age (2 10 days); the third group (26 children), 18 months of age (2 10 days) and the fourth group (25 children), 24 months of age (t 10 days). The parents or responsible persons gave informed written consent for participation of the children in the study.
’ Source: Health Ministry of Brazil, 1996.
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Biochemical analvses: A 6 ml sample of peripheral venous blood was collected f?om each child after a 6 hour fast for biochemical analyses. The samples were protected from light and analyzed for serum retinal, zinc and iron levels and for total iron binding capacity (TIBC). Hemoglobin levels and hematocrit were also determined. Serum retinol levels were determined by rapid isocratic high performance liquid chromatography (HPLC) procedure (21). HPLC was performed using a Kontron Instruments@ model T414 apparatus with a Cl8 type column (OD5 - 25 cm x 0.46 cm). The eluent was dichloromethane-acetonitrile-methanol (20:70:10. v/v/v), with a flow of 2 ml/min, and retinol readings were taken at 325 mn wavelength. According to WHO criteria (3), retinol levels < 0.70 p mol/l were considered to be deficient. For zinc analysis, blood was collected into heparinized tubes appropriate for trace element collection. Serum zinc levels were analyzed by atom absorption spectrophotometry and were considered to be deficient when they were below 50 &dl. For hemoglobin and hematocrit analysis, blood was collected into tubes containing ethylenediaminetetraacetic acid (EDTA). Hemoglobin and hematocrit were determined with automatic T890 or STKS CoulterB counters which use electrical impedance for cell counts. Hemoglobin levels higher than 11 .O g/d1 were considered normal. For serum iron and TIBC measurement we used an atom absorption system (Cobas Integra - Roche@). Serum iron levels below 50 pg/dl and transferrin saturation levels < 16% were considered to be deficient. Blood for analysis of serum iron and TIBC was collected into tubes containing no anticoagulant. Non-biochemical analyses: The presence of xerophthalmia was determined by one of the authors by direct inspection of the bulbar conjunctiva under natural light, searching for conjunctival drying and folding, Bitot spots and cornea1 scars. Anthrompometric data (weight and length) were obtained at the time of blood collection for the study from the medical records of the children. The children were Wly undressed and their length was measured in the supine position. The nutritional status of the children was classified on the basis of the reference values for height/age and weight/height of the US National Center for Health Statistics (NCHS). Children were classified as stunting when they presented a < - 2 Z score of NCHS reference values for height/age and as wasting when they presented a < - 2 Z score of NCHS reference values for weight/height. In the present study, the breast-feeding period was considered to be the time during which the child was fed human milk exclusively or not and the end of this period was considered to be the time when the child did not receive the maternal breast at any time during the day (weaning). Birth weight was obtained directly f?om the medical records of the children. A child was considered to be of low birth weight when its birth weight was less than 2500 g (3). Monthly income was considered to be the sum of all salaries and other types of monthly earnings (renting goods or real estate, meal tickets, etc.) of all household members calculated in US dollars, multiplied by 12 and then divided by the number of household residents in order to obtain the per capita income.
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To determine the correlation between parental educational used a study period of at least 8 years as the cut-off point.
level and risk for VAD, we
Statistical analyses: To determine the possible correlations of risk factors for VAD we applied the chi-square test (x2); to calculate the trends of the proportions of children with retinol below the cut-off point in the various age ranges we used the ~2 test for linear trends; the Bartlett test for homogeneity of variances and analysis of variance (ANOVA) were applied to compare mean serum retinol levels for the various age ranges; to compare the mean values for the two groups of children (with an without VAD) we used the Student’s t test for the means of two non-correlated populations. To calculate the interval of the proportion of children with VAD we calculated the confidence interval for a population. The level of significance was set at a = 0.05 (5%) for all the analyses performed. The study was approved by the Ethics Committee Medicine, University of Sb Paulo.
of the University
Hospital, Faculty of
RESULTS Freouencv of VAD in the study arouv: We detected 22 children (21.4%; 95% confidence interval (CI) = 13.5 - 29.3 %) with retinol levels I 0.70 ymol/l (Table 1). Although there was no significant difference between the different age ranges studied, we noted that the age range including the highest proportion of children with retinol level I 0.70 pmol/l was the 24 month range [x2 (3 d.E) = 7.16; p=O.O67; OR = 1.00 at 6 months of age, OR = 0.60 at 12 months of age, OR = 0.80 at 18 months of age, and OR = 2.93 at 24 months of age].
TABLE 1 Proportion of Children with Retinol Levels I 0.70 pmoY1 and with > 0.70 pmovl According to Age Range -,l^s,l-,,.-,..~l_,~-,--,~,-,,,,~-,, ~~_l*-ll,ll~~~ll”ll,~,“,,~,,~,..,-”~.~~,”.,,~,~~~ i-l,.,,.-l. 13111.,~iYi”l~,~_-~~~-_,-,_(--_,,“,-,,“,-~,-“~~-~,~-.~~ Serum retinol % Serum retinol % Mean senmr retinol Total MP Age level (? 2SD) @or+) <0.7O,pmol/l > 0.70 pmol/l i‘ 6 5 18.5 22 81.5. o.~ot (d.60) _..._._(n>.. 27 (0.30X79$ 1.14 (0.74) 25 (0.67-2.07) 3 18 4 15.4 22 84.6 0.98 (0.62) 26 (0.38-1.64) 4 24 10 40.0 15 60.0 0.96 (0.89) 25 (0.37-2.06) 81- ,,..,_._,.., 78.6 1-.“ .oo 103 -.Total -,.-. .- --._ --., .--,,.,. -., ,_-. -_ 22 .,-,,._....,,-.-,- 21.4* ,_,.._,..,,.,,-_, I(-,,.,,_._ ,,.” ..,,_, -,,“~-_._,--,_.,-._._ “-,“(0.77) ,-,,,----* 95% Confidence interval (CI) (95 %) = 13.5-29.3 %; ~2 (3 d.f.) = 7.16; p=O.O67. # The numbers in parenthesis correspond to the lowest and highest serum retinol values detected in the group, in pmol/l. 2
12
3
tThere were no significant p=O.107). ll (PmoW.
12.0
differences
22
88.0
among the different
age groups (ANOVA:
F=2.082;
VITAMIN A DEFICIENCY
IN CHILDREN
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The overall mean serum retinol value was 1.00 pmol/l(2SD + 0.77 pmol/l). No case of xerophthahnia was detected during the inspection of the children’s conjunctiva. The 12~month-old group presented the highest mean serum retinol value compared to the other groups (1,3 and 4), but there were no significant differences among the different age groups (Bartlett test: p=O.207; ANOVA: F=2.082; p=O. 107 - Table 1). Difference in mean serum retinol levels between sexes: No significant sex differences were detected with respect to mean serum retinol levels or frequency of children with VAD (Table 2), with mean retinol values of 0.98 pmol/l (2SD + 0.66 pmol/l) for boys and 1.00 pmoY1 (2SD + 0.83 pmoV1) for girls @=0.103); no significant sex differences were observed in VAD prevalence, with 12153 (22.6%) boys and 10150 (20.0%) girls presenting retinol levels I 0.70 pmoY1 (~2 = 0.11; p= 0.744).
TABLE 2 Proportion of Children with Retinol Levels I 0.70 pmol/l and > 0.70 pmol/l According to Sex % Total Serum--l_.-.-.l retinol I 0.7O_cunoVl > 0.7O~moYl -_.- .._..__._ % _.Serum ..-.__ retinol ._ ..__,,, _,.___,__ 12 77.4 53 41 22.6* 10 40 80.0 50 20.0* 22 21.4 78.6 103 Total __*________,~_______.,,___. __,..._,._, --,* _...I.. L-II”,Y..I ,.,81 “,.-X,__i,-,..*_- _,l_,_E__-l__l___l_ *No Significant Sex Male Female
Freuuencv of zinc deficiencv among deficient serum zinc levels (O/98). The pg%). Children with VAD presented children without VAD presented mean
children with and without VAD: No children showed overall mean serum zinc level was 108.9 pg% (2SD k 43.1 mean zinc levels of 105.1 pg% (2SD ~44.1 pg%) and zinc levels of 110.0 pg% (2SD + 42.3 pg%) (p=O.23 1).
VAD and breast-feeding: With respect to breast-feeding, the groups of children with VAD presented a mean duration of breast-feeding of 6.1 months, while the children without VAD presented a mean of 8.6 months, corresponding to a significant difference (pcO.05) between groups. Freauencv of anemia and/or iron deficiencv among; children with and without VAD: Again no significant differences in frequency of anemia and/or signs of iron deficiency were detected between groups, although anemia was more frequent among children with VAD (Table 3). In the group with VAD we detected 19121 (90.5%) children with signs of anemia and/or iron deficiency, whereas in the group without VAD we detected 49/69 (71.0%) children with these signs (Yates ~2 = 2.33; p = 0.126). The prevalence of anemia and/or signs of iron deficiency was usually elevated in the groups studied. Considering the two groups of children as a whole, 68190 (75.6 %) of them presented some signs of anemia and/or iron deficiency in laboratory tests. Parental educational level and VAD: No significant differences in parental schooling were detected between groups; 11116 (68.7 %) parents of children with VAD and 40/66 (60.6%) parents of children without VAD did not have at least 8 years of study (~2 = 0.36; p= 0.547). Also, no significant difference in maternal schooling was observed between groups; 12/21 (57.1 O/o)mothers of children with VAD and 47/80 (58.7%) mothers of children without VAD did not have at least 8 years of study (x2 = 0.02; p= 0.894). No significant differences were observed when having at least one of the parents with eight or more years of schooling was considered as a
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I.S. FERRAZ et al.
risk factor, with 12/21 (57.1 %) of the children with VAD and 38/80 (48.7) of the children without VAD not having at least one parent or a person responsible with at least eight years of study (x2 = 0.47; p = 0.494) (Table 3). In general, considering the two groups of children (with and without VAD), we observed that 51/82 (62.2 %) fathers and 59/101 (58.4 %) mothers had not studied for at least 8 years; at the same time we observed that 51/101 (50.5 %) of the children studied did not have at least one parent with at least 8 years of schooling. The general illiteracy rate for fathers and mothers as a whole was 2.2 % (4/182), with 21101 (2.0%) mothers being illiterate. Only 4.9% (g/182) of the fathers and mothers as a whole whose educational level was known succeeded in obtaining higher education.
TABLE 3 Frequency of Some Risk Factors for VAD Among the Children Studied According to Vitamin A Status 1 Risk factor (%) Presence of anemia I at&or iron deficiency Absence of anemia and/or iron deficiency Father with less than 8 yearsof formal education Father with at least 8 years of formal education Mother with less than 8 years of formal education Mother with at least 8 years of formal education Neither parent with at least 8 years of formal education Father and/or mother with at least 8 years of formal education Birth weight < 2.5OOg Birth weight 1 2.500 g N.S. = No Significant.
Children with VAD (%) 19/21 (90.5)* 2121 (9.5) 11/16 (68-V
1Children without VAD (%) 1 Notes (*)N.S 49169 ’’ (71.0)* 20169 (29.0) 40166 (t1N.S. (60.6) t
5116 (31.3)
26166 (39.4)
12121 (57.1X
47180 (58.8) $
9121 (42.9)
33180 (41.2)
12/21 (57.1)#
39180 (48.8) #
9121 (42.9)
41/80 (51.2)
4121 (19,O)f 17/21 (81 .O)
5180 (6,2)& 75180 (93.8)
(S)N.S.
(#)N.S
(E)N.S.
Prematuritv and/or low birth weight and VAD: Although there was no significant difference between groups with respect to low birth weight, a higher proportion of birth weight < 2,500 g was observed in the group of children with VAD (Table 3) with 4121 (19.0%) low birth weight
VITAMIN A DEFICIENCY
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763
children in the group with VAD and 5/80 (6.2%) in the group without VAD (exact Fisher test; p = 0.086). As a whole, 9/101 (8.9 %) children were of low birth weight. Per canita income and VAD: Again, no significant differences in annual per capita income was observed between the two groups of children The per capita income of the families of children with VAD was closely similar, but slightly higher, than that of the families of children without VAD, i.e., US% 2,415.60 as opposed to US$2,147.28 (p = 0.222), respectively. Number of household members and VAD: The overall mean number of persons residing in the same household was 4.9 (2SD k 3.63) per domicile. When considered separately, the children with VAD lived in households with 4.7 persons (2SD +_4.03) on average, and the children without VAD lived in households with 4.9 persons (2SD + 3.54) on average, with no significant difference between these values (p=O. 159). Nutritional status and VAD: In the present study, no child (O/94) was classified as wasting or stunting according to NCHS curves.
DISCUSSION Although mean serum retinol levels do not represent vitamin A status at concentrations defined as physiological, it is generally agreed that, under normal conditions, serum retinol levels I 0.70 pmoY1 reflect low hepatic stores of the vitamin (3). Serum retinol was I 0.70 urnoF in 22/103 (21.4%) children, with 1 of these children (1.0%) presenting serum retinol levels below 0.35 pmol/l. This index is above the 20% established as a severe public health problems in communities by the WI-IO (3). Although no child presented xerophthahnia, it is known that even a mild deficiency can increase infant morbidity and mortality rates, especially due to both diarrhea1 and respiratory tract diseases (8, 22), a very important fact in a country where the tiequencies of these diseases are considered to be moderately elevated. These values are lower than those reported by Favaro et al (6) who, in a study of children aged 2 to 8 years in the periurban region of the city, detected 1.8 % of children with retinol levels below 0.30 pmol/l and 48.8% with levels below 0.70 pmoY1; however, in the cited study calorimetric methods rather than HPLC were used for retinol measurement. The results of the present study resemble those reported by GoncalvesCarvalho et al (5), who detected a 17.6% prevalence of serum retinol levels between 0.30 umol/l and 0.70 pmol/l among preschool children living in the slums of the municipality of Campinas (S~O Paul0 State), and are also closely similar to those detected by Rodriguez et al (23) among 12 to 59-month old children in Equador. Outside Latin America, but still in developing countries, Tafesse et al. (24), in a study of Ethiopian children aged 6 months to 6 years, detected a prevalence of 31.9% and 48.9% of serum retinol levels < 0.35 urnoF and ranging from 0.35 to 0.69 umoY1, respectively. The overall mean retinol level was 1.00 umoVl(2SD + 0.77 umoV1) in our study. The age range showing the highest mean serum retinol concentration was that of 12 months of age, with a mean of 1.14 urnoF (2SD ? 0.74 pmol/l), although there was no significant difference between the means for the different age ranges. In addition, these differences may not represent differences in clinical practice since, as mentioned earlier, mean serum retinol levels do not represent vitamin A status at concentrations defined as physiological. Although there are conflicting data about the age range of highest risk for VAD in childhood (3, 25, 26), in our study, 24-month-old children presented the highest prevalence of serum retinol levels I 0.70 umol/l, even though the difference was not statistically significant. A probable explanation for this finding may be the fact that the
764
I.S. FERRAZ et al.
children belonging to this group were under the “protective” effect of breast-feeding to a lesser extent than the other groups, when we consider that breast-feeding proved to protect children from VAD (see discussion below). However, dietary surveys are needed to answer these questions. Despite the controversies, some studies have shown a higher prevalence of VAD in males (9, 27, 28) a fact that was not observed in our study. Mean senmr retinol levels were closely similar for the two sexes: 0.98 pmoY1 for boys and 1.OOpmoY1 for girls (p-0.103); 12/53 (22.6%) boys and lo/50 (20.0%) girls presented serum retinol levels I 0.70 pmoYl(x2 = 0.11; p= 0.744). A significant proportion of the children studied presented signs of anemia and/or iron deficiency [68/90 (75.6%)]. Again no significant differences were observed between the two groups of children with and without VAD with respect to the presence of signs of anemia in peripheral blood and/or iron deficiency. Thus, this indicator was found not to be a risk factor for VAD among the children studied. However, the high prevalence of retinol levels I 0.70 mnoY1 and of anemia and/or iron deficiency show that nutritional deficiencies are not selective in this community, demonstrating that feeding habits must have improved due to improved living conditions ot to educational campaigns, or yet again to supplemental feeding programs, or to all of these factors together. Despite the importance of serum retinol levels I 0.70 pmoYl, and of anemia and/or iron deficiency, in the present study, no child showed serum zinc levels below values considered normal in either group. As observed in animals (15) and also in human beings (16), the trace element zinc plays an important role in RBP synthesis by the liver, so that its deficiency may be a factor for the development of VAD (14). Also, no significant differences in mean serum zinc levels were detected between groups. This observation rules out the possibility of zinc having interfered with the low serum retinol levels in the children with VAD studied here. Several authors have studied the effect of adverse social conditions on the development of VAD (26, 29-31). In the present study we investigated the per capita income - inferred from monthly per capita income - of the families of the children under study as a way to estimate the acquisitive power of this population and to determine whether this factor might affect vitamin A status. The general per capita income was US$2,147.28 per year, corresponding to less than half the Brazilian per capita income in 1997 (US$ 4,743). However, even though this value corresponds to less than half the per capita income for the country, the inequality of income distribution in Brazil is notorious. These children definitely do not belong to the most underprivileged classes in the community, so that the detection of these nutritional deficiencies in the study group becomes even more worrisome. As indicated earlier, the mean number of persons residing in a household usually was 4.9. We thus obtain mean monthly earnings per domicile of US% 876.81. However, further studies are needed for a better economic characterization of our population. The per capita income of the families of children with VAD was slightly higher than that of the families of children without VAD (approximately US$2,415.60 and US$2,147.28 per year, respectively; p = 0.222). Thus, per capita income did not prove to be a risk factor for VAD in the present study, perhaps owing to the relatively reduced number of children studied and also to the absence of wide variation in family income. Because of the relatively small number of children investigated in the present study, these infants are not representative of all children in this age range in the community. Despite the social indicators shown here (per capita income and educational level), at the local level these children belong to the so-called “low” middle class and not to the most underprivileged social classes, a fact that increases the concern about the prevalence of VAD detected. Thus, the present study reveals the occurrence of VAD - even in a subclinical form - among children seen at a puericulture outpatient clinic linked to the local university who were apparently healthy and not
VITAMIN A DEFICIENCY
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malnourished since no child was classified as wasting or stunting in the present study. This fact has been reported by some investigators (32), showing that the combination of VAD with the absence of wasting or stunting is possible. The mean number of persons per household was similar for both groups. Thus, we cannot state that, in this case, the number of persons in the family represented a risk factor for VAD, although some authors (18,253 1) have reported that children from families with a larger number of persons presented lower retinol levels than children from less numerous families. Although the WHO (3) and some authors have shown a correlation between low educational level and VAD (25, 29, 33), no differences in educational level were found between the parents of the two groups of children in the present study when the mother alone or the father alone was considered, or at least one of the parents, showing that parental educational level is not a risk factor for VAD in this study. Perhaps the lack of significance of this difference was due to the low educational level of the parents in both groups in general, since more than half the children (50.5%) did not have at least one of the parents with more than eight years of schooling. A significant difference was detected between the means for the two groups of children with respect to time of breast-feeding, i.e., the group with VAD (6.1 months) and the group without VAD (8.6 months; ~~0.05). The mean time of breast-feeding for the children with VAD was similar to the values detected by the WHO (34) in economically favored urban populations, in which breast-feeding was rarely offered beyond the sixth month of life, whereas in less favored communities half the mothers still offered their milk to their children at 18 months of age. The group of children without VAD represented a group with an intermediate breast-feeding pattern. Thus, the relatively short time of breast-feeding adopted by economically underprivileged classes witbout the necessary economic and educational support for the acquisition of a diet replacing breast-feeding with foods rich in vitamin A may be one of the factors responsible for the observed VAD, since, as previously observed by others, we noted that breast-feeding seems to “protect” the child against the development of VAD (4, 17-19), since maternal milk contains good concentrations of this vitamin especially during the first postpartum days (20) and in some places it may represent the only dietary source of the vitamin (17, 35). Furthermore, maternal milk, by containing other “anti-infectious” components, reduces the morbidity and impact of infections that induce the loss of vitamin A and increase its requirements by the organism, a fact that may lead to deficiency in children (3). However, further studies on the breast-feeding patterns and the local weaning diets, such as those conducted using alimentary surveys, are necessary for a better elucidation of the real and precise causes of this nutritional deficiency. Prematurity and/or low birth weight also are risk factors for the development of VAD (3), as previously shown by several authors (36-38). The probable explanation for prematurity as a risk factor for VAD is that RBP synthesis by the fetal liver and hepatic deposits of this vitamin occur during the last weeks of pregnancy, as also demonstrated in animals (39), whereas children born at term but with a low birth weight may also have low reserves due to maternal and fetal mahmtrition (3). Although no significant differences were observed between groups, children with VAD tended to have a more frequent history of low birth weight than children without VAD (exact Fisher test: p = 0.086), despite the instruction given to the first group about vitamin supplementation. The study of a larger number of children may indicate a greater importance of the relationship between low birth weight and/or prematurity and the development of VAD. It is known that premature and/or low birth weight children often belong to families of low socioeconomic conditions, a fact that may also influence vitamin a status, although &rther study is needed to test this hypothesis. Furthermore, studies are needed about the efficacy of the dose
I.S. FERRAZ et al.
and parental compliance with the administration of vitamin supplementation to premature and/or low birth weight children, as well as studies of other forms of vitamin supplementation. Final considerations The present study raises various questions still awaiting an answer but shows that the problem of vitamin A deficiency is present in Southeast Brazil and that actions should be taken to combat it, especially by stimulating breast-feeding, providing the opportunity for new investigations in an attempt to explain other factors underlying one more nutritional deficiency among Brazilian children.
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10.Fawzi WW, Herrera MG, Willet WC, Nestel P, El Amin A, Mohamed KA. Dietary vitamin A intake and the incidence of diarrhea and respiratory infection among Sudanese children JNutr 1995; 125:1211-21. 11 .Hossain S, Biswas R, Kabir I, Sarker S, Dibley M, Fuchs G, Mahalanabis D. Single dose vitamin A treatment in acute shigellosis in Bangladeshi children: random&d double blind
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controlled trial. BMJ 1998; 3 16:422-6. 12Rahmathullah MB, Underwood BA, Thulasiraj RD, Milton RC, Ramaswamy K, Rahmathullah R, Babu G. Reduced mortality among children in Southern India receiving a small weekly dose of vitamin A. N England J Med 1990; 323:929-35. 13.Ghana VAST Study Team Vitamin A supplementation in Nothern Ghana: effects on clinic attendances, hospital admissions, and chidren mortality. Lancet 1993; 342: 7-12. 14.Udomkesmalee E, Dhanamitta S, Sirisinha S, Charoenkiatkul, Tunyipopipat S, Banjong 0, Rojroongwasinkul N, Kramer TR, Smith Jr JC. Effect of vitamina A and zinc supplementation on the nutriture of children in Northeast Thailand. Am J Clin Nutr 1992; 5650-7. 15. Smith JE, Brown ED, Smith JC. The effect of zinc deficiency on the metabolism binding protein in the rat. J Lab Clin Med 1974; 84:692-7. 16.Hustead VA, Greger JL, Gutcher GR. Zinc supplementation vitaminAinpretermir&nts AmJClinNutr 1988; 47:1017-21.
of retinol-
and plasma concentration
of
17.Tarwotjo MSI, Sommer A, Soegiharto BST, Susanto D, Muhilal. Dietary paractices and xerophtahnia among Indonesian children. Am J Clin Nutr 1982; 35:574-8 1. 18.Stanton BF, Clemens JD, Wojtyniak nutritional blindness in urban Bangladesh.
B, Khair T. Risk factors for developing Am J Dis Child 1986; 140:584-8.
mild
lg.Mahalanabis D. Breast feeding and vitamin A deficiency among children attending diarrhoea treatment centre in Bangladesh: a case-control study. BMJ 1991; 303:493-6. 20.Lesher M, Broody JK, Williams 70: 182-92.
a
HH, Macy IG. Human milk studies. Am J Dis Child 1945;
2 1 Arnaud J, Fortis I., Blachier S, Kia D, Favier A. Simultaneous determination of retinal, CLtocopherol and p-carotene in serum by isocratic high-performance liquid chromatography. J Chromatogr 1991; 572: 103-26. 22.Milton RC, Reddy V, Naidu NA. Mild vitamin A deficiency Indian experience. Am J Clin Nutr 1987; 46: 827-9.
and childhood
morbidity
- an
23.Rodriguez A, Guaman G, Nelson DP. Vitamin A status of chidren in five Ecuadorian provinces. Bull Pan Am Health Organ 1996; 30(3):234-41. %.Tafesse Y, Fisseha T, Umeta M, Hidar J, Teka W. Vitamin A deficiency: in Dodota district in central Ethiopia. East Afr Med J 1996; 73(5):303-7.
a serious threat
25.Kjolhede CL, Stallings, Dibley MJ, Sadjimin T, Dawiesah S, Padmawati S. Serum retinol levels among preschool children in Central Java: demographic and socioeconomic determinants. Int J Epidemiol 1995; 24:399-403.
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26.Hussain A, Kvale G. Serum vitamin A in relation to socio-economic, demographic dietary characteristics in Bangladesh children. Acta Paediatric 1996; 85:971-6.
and
27.Brilliant LB, Pohkrel RP, Grasset NC, Lepkowski JM, Kolstad A, Hawks W, Pararajasegaram R, Brilliant GE, Gilbert S, Shresha SR, Kuo J. Epidemiology of blindness in Nepal. Bull WHO 1985: 63(2):375-86. 28.Nestel P, Herrera MG, El Amin A, Fawzi W, Mohamed KA, Weld, L. associated with xeroftahnia in Northern Sudan J Nutr 1993; 123:2115-21.
Risk factors
29.Cohen N, Rahman H, Sprague J, Jalil MA, Leemhuis De Regt E, Mitra M. Prevalence and determinan ts of nutritional blindness in Bangladesh children. Wld Hlth Statist Quart, 1985; 38:3 17-30. 3o.Mele L, West Jr KP, Kusdiono, Pandji A, Nendrawati H, Tilden RL, Tarwotjo I, Aceh Study Group. Nutritional and household risk factors for xerophthahnia in Aceh, Indonesia: a case-control study. Am J Clm Nutr 1991; 53:1460-5. 3 1. Ahmed F, Mohiduzzaman M, Barua S, Shaheen N, Margetts BM, Jackson AA. Effect of family size and income on the biochemical indices of urban school children of Bangladesh. Eur J Clin Nutr 1992; 46:465-73. 32.Pacheco Santos LM, Dricot JM, Asciutti LS, Dricot-D’ans C. Xerophtahnia in the state of Paraiba, northeast of Brazil: clinical findings. Am J Clin Nutr 1983; 38:139-44. 33.Gittelsohn J, Shankar AV, West Jr KP, Ran practices reflect antecedent risk of xerophthahnia 5 1:484-90.
R, Dhungel C, Dahal B. Infant feeding in Nepali children. Eur J Clin Nutr 1997;
34.World Health Grganization. Contemporary patterns of breast-feeding: Collaborative Study on breast-feeding. Geneva, 1981.
Report on the WHO
35.Gebre-Medhin M, Vahlquist A, Hofvander Y, Upptill L, Vahlquist B. Breast milk composition in Ethiopian and Swedish mothers. I. Vitamin A and p-carotene. Am J Clin Nutr 1976; 29:441-51. 36.Brandt RB, Mueller DG, Schroeder JR, Guyer KE, Kirkpatric BV, Hutcher FE. Serum Vitamin A in premature and term neonates J Pediatr 1978; 92: 101-4. 37.Shenai ‘JP, Chytil F, Stahhnan MT. neonates. Pediatr Res 1985; 19:892-3.
NE, Erlich
Liver Vitamin A reserves of very low birth weight
38.Tolba AM, Hewedy FM, Al-Senaidy AM, Al-Gthman AA. Neonates’ vitamin A status in relation to birth weight, gestational age, and sex. J Trop Pediatr 1998; 44: 174-7. 39.Takahashi YI, Smith JE, Goodman DS. Vitamin A and retinal-binding protein metabolism during fetal development in the rat. Am J Physiol 1977; 233(4):E263-E272. Accepted
for
publication
November
3, 1999.
VITAMIN A DEFICIENCY
PII: SO271-5317(00)00177-9
IN CHILDREN AGED 6 TO 24 MONTHS IN SAO PAUL0 STATE, BRAZIL
IS Ferraz, M.D. ‘*, JC Daneluzzi, Ph.D. I, H Vannucchi, Ph.D.2 1 Department of Child Care and Pediatrics, Faculty of Medicine of Ribeirgo Preto, University of Sb Paulo. 2 Department of Internal Medicine - Division of Clinical Nutrology, Faculty of Medicine of Ribeirgo Preto, University of Sb Paulo. ABSTRACT Vitamin A deficiency (VAD), mainly the subclinical form, is endemic in several areas of the Brazilian Northeast. However, studies concerning its prevalence and etiology (risk factors) in urban areas of Sgo Paul0 State are lacking. The objective of the present study was to identify VAD and the risk factors among children attending a Child Care outpatient clinic in Ribeirso Preto city, Szo Paul0 State, Brazil. A total of 103 children aged 6 to 24 months without any diarrhea or fever illness were selected from a pediatric outpatient clinic. A careful clinical history and physical examination provided information about breast-feeding, parental education, family income, family size, birth weight and anthropometric data. The children also underwent ophthalmologic examination to check for signs of xerophthalmia and were submitted to blood tests in order to determine hemoglobin and serum iron, zinc and retinol levels. Serum retinol levels E 0.70 pmol/l are considered to be deficient by the World Health Organization. Retinol levels, determined by high performance liquid chromatography (HPLC), were E? 0.70 p?mol/l in 22 children (21.4%). No child had xerophthalmia. The overall mean serum zinc level was 108.9 pg% (2SD + 43.1 pg%) and the values for children with and without VAD were 105.1 pg% (2SD + 44.1 pg%) and 110.0 pg% (2SD + 43.2 pg%) respectively, with no child presenting serum zinc levels below the normal range. None of them showed a
Breast-feeding,
Child, Zinc.
I* Corresponding Author: Faculty of Medicine of RibeirZo Preto, Department of Child Care and Pediatrics, University of S5o Paula, Av. Bandeirantes, 3900. 14049-900. Ribeirgo Preto, SP, Brazil. Telephone and FAX number: 16-633-0136
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INTRODUCTION Although the deleterious effect of vitamin A deficiency on the organism have been known since the first quarter of the present century (l), vitamin A deficiency (VAD) continues to be a public health problem in several parts of the world especially in developing countries (2). Although it considers VAD to be of low magnitude on the American continent, the WHO (3) has pointed out some high-risk areas for VAD such as Haiti and some regions of Brazil. In Brazil, xerophthahnia was first described in the past century in slave children aged 1 to 7 years living in Rio de Janeiro (4). Although VAD is known to occur in the Northeast region of Brazil (4), considered to be the region most economically underprivileged in the country, scarce reports of the occurrence of VAD have been recently published concerning the Southeast region (5, 6), considered to be the richest in the country, the State of Sb Paul0 in particular. In view of the various functions of vitamin A in the organism - improved immune function with reduced susceptibility to infections (7) - and the consequences of its deficiency in the organism - increased risk of morbidity and mortality in populations at risk (8-11) -, in addition to reports of improved childhood morbidity and mortality rates in places where this problem has been fought, (12, 13), the importance of studying VAD is clear, especially in a locality where children present high morbidity rates due to respiratory and diarrheic diseases and where infant mortality still reaches worrisome rates (25/1,000 liveborns’). In addition, the search for eventual risk factors may help plan strategies to combat this nutritional deficiency. Several risk factors for VAD exist (3): protein-energy malnutrition (PEM), low prevalence of breast-feeding, low consumption and low availability of foods rich in vitamin A, low income with consequent precarious living conditions, high prevalence of low birth weight, low educational level of the parents, high prevalence of febrile and parasitic diseases, and precarious basic sanitation conditions. Furthermore, serum zinc levels can also interfere with serum vitamin A levels (14) since this trace element participates in the synthesis of retinol binding protein @BP) (15, 16). In addition, due to its adequate content of vitamin A and of “anti-infectious” components, human milk seems to protect infants against the development of VAD and of its consequences (4, 17-20), especially during the first six years of life (3). The objective of the present study was to determine the presence of VAD among children considered to be healthy aged 6 to 24 months, living in an urban area of the town of de Rib&b Preto (Sb Paulo), regularly followed up at a Puericulture outpatient clinic with the assistance of the local university. Some of the probable risk factors for the development of this deficiency in the community were also investigated.
SUBJECTS Subiect recruitment: A total of 103 children aged 6 to 24 months regularly followed at the unit and presenting no acute episodes of fever and/or diarrhea - regardless of a previous history of morbidity - were included in the study, which lasted corn June 1997 to March 1998. The children were divided into four groups according to age range: the first group (27 children), 6 months of age (k 10 days); the second group (25 children), 12 months of age (2 10 days); the third group (26 children), 18 months of age (2 10 days) and the fourth group (25 children), 24 months of age (t 10 days). The parents or responsible persons gave informed written consent for participation of the children in the study.
’ Source: Health Ministry of Brazil, 1996.
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IN CHILDREN
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Biochemical analvses: A 6 ml sample of peripheral venous blood was collected f?om each child after a 6 hour fast for biochemical analyses. The samples were protected from light and analyzed for serum retinal, zinc and iron levels and for total iron binding capacity (TIBC). Hemoglobin levels and hematocrit were also determined. Serum retinol levels were determined by rapid isocratic high performance liquid chromatography (HPLC) procedure (21). HPLC was performed using a Kontron Instruments@ model T414 apparatus with a Cl8 type column (OD5 - 25 cm x 0.46 cm). The eluent was dichloromethane-acetonitrile-methanol (20:70:10. v/v/v), with a flow of 2 ml/min, and retinol readings were taken at 325 mn wavelength. According to WHO criteria (3), retinol levels < 0.70 p mol/l were considered to be deficient. For zinc analysis, blood was collected into heparinized tubes appropriate for trace element collection. Serum zinc levels were analyzed by atom absorption spectrophotometry and were considered to be deficient when they were below 50 &dl. For hemoglobin and hematocrit analysis, blood was collected into tubes containing ethylenediaminetetraacetic acid (EDTA). Hemoglobin and hematocrit were determined with automatic T890 or STKS CoulterB counters which use electrical impedance for cell counts. Hemoglobin levels higher than 11 .O g/d1 were considered normal. For serum iron and TIBC measurement we used an atom absorption system (Cobas Integra - Roche@). Serum iron levels below 50 pg/dl and transferrin saturation levels < 16% were considered to be deficient. Blood for analysis of serum iron and TIBC was collected into tubes containing no anticoagulant. Non-biochemical analyses: The presence of xerophthalmia was determined by one of the authors by direct inspection of the bulbar conjunctiva under natural light, searching for conjunctival drying and folding, Bitot spots and cornea1 scars. Anthrompometric data (weight and length) were obtained at the time of blood collection for the study from the medical records of the children. The children were Wly undressed and their length was measured in the supine position. The nutritional status of the children was classified on the basis of the reference values for height/age and weight/height of the US National Center for Health Statistics (NCHS). Children were classified as stunting when they presented a < - 2 Z score of NCHS reference values for height/age and as wasting when they presented a < - 2 Z score of NCHS reference values for weight/height. In the present study, the breast-feeding period was considered to be the time during which the child was fed human milk exclusively or not and the end of this period was considered to be the time when the child did not receive the maternal breast at any time during the day (weaning). Birth weight was obtained directly f?om the medical records of the children. A child was considered to be of low birth weight when its birth weight was less than 2500 g (3). Monthly income was considered to be the sum of all salaries and other types of monthly earnings (renting goods or real estate, meal tickets, etc.) of all household members calculated in US dollars, multiplied by 12 and then divided by the number of household residents in order to obtain the per capita income.
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To determine the correlation between parental educational used a study period of at least 8 years as the cut-off point.
level and risk for VAD, we
Statistical analyses: To determine the possible correlations of risk factors for VAD we applied the chi-square test (x2); to calculate the trends of the proportions of children with retinol below the cut-off point in the various age ranges we used the ~2 test for linear trends; the Bartlett test for homogeneity of variances and analysis of variance (ANOVA) were applied to compare mean serum retinol levels for the various age ranges; to compare the mean values for the two groups of children (with an without VAD) we used the Student’s t test for the means of two non-correlated populations. To calculate the interval of the proportion of children with VAD we calculated the confidence interval for a population. The level of significance was set at a = 0.05 (5%) for all the analyses performed. The study was approved by the Ethics Committee Medicine, University of Sb Paulo.
of the University
Hospital, Faculty of
RESULTS Freouencv of VAD in the study arouv: We detected 22 children (21.4%; 95% confidence interval (CI) = 13.5 - 29.3 %) with retinol levels I 0.70 ymol/l (Table 1). Although there was no significant difference between the different age ranges studied, we noted that the age range including the highest proportion of children with retinol level I 0.70 pmol/l was the 24 month range [x2 (3 d.E) = 7.16; p=O.O67; OR = 1.00 at 6 months of age, OR = 0.60 at 12 months of age, OR = 0.80 at 18 months of age, and OR = 2.93 at 24 months of age].
TABLE 1 Proportion of Children with Retinol Levels I 0.70 pmoY1 and with > 0.70 pmovl According to Age Range -,l^s,l-,,.-,..~l_,~-,--,~,-,,,,~-,, ~~_l*-ll,ll~~~ll”ll,~,“,,~,,~,..,-”~.~~,”.,,~,~~~ i-l,.,,.-l. 13111.,~iYi”l~,~_-~~~-_,-,_(--_,,“,-,,“,-~,-“~~-~,~-.~~ Serum retinol % Serum retinol % Mean senmr retinol Total MP Age level (? 2SD) @or+) <0.7O,pmol/l > 0.70 pmol/l i‘ 6 5 18.5 22 81.5. o.~ot (d.60) _..._._(n>.. 27 (0.30X79$ 1.14 (0.74) 25 (0.67-2.07) 3 18 4 15.4 22 84.6 0.98 (0.62) 26 (0.38-1.64) 4 24 10 40.0 15 60.0 0.96 (0.89) 25 (0.37-2.06) 81- ,,..,_._,.., 78.6 1-.“ .oo 103 -.Total -,.-. .- --._ --., .--,,.,. -., ,_-. -_ 22 .,-,,._....,,-.-,- 21.4* ,_,.._,..,,.,,-_, I(-,,.,,_._ ,,.” ..,,_, -,,“~-_._,--,_.,-._._ “-,“(0.77) ,-,,,----* 95% Confidence interval (CI) (95 %) = 13.5-29.3 %; ~2 (3 d.f.) = 7.16; p=O.O67. # The numbers in parenthesis correspond to the lowest and highest serum retinol values detected in the group, in pmol/l. 2
12
3
tThere were no significant p=O.107). ll (PmoW.
12.0
differences
22
88.0
among the different
age groups (ANOVA:
F=2.082;
VITAMIN A DEFICIENCY
IN CHILDREN
761
The overall mean serum retinol value was 1.00 pmol/l(2SD + 0.77 pmol/l). No case of xerophthahnia was detected during the inspection of the children’s conjunctiva. The 12~month-old group presented the highest mean serum retinol value compared to the other groups (1,3 and 4), but there were no significant differences among the different age groups (Bartlett test: p=O.207; ANOVA: F=2.082; p=O. 107 - Table 1). Difference in mean serum retinol levels between sexes: No significant sex differences were detected with respect to mean serum retinol levels or frequency of children with VAD (Table 2), with mean retinol values of 0.98 pmol/l (2SD + 0.66 pmol/l) for boys and 1.00 pmoY1 (2SD + 0.83 pmoV1) for girls @=0.103); no significant sex differences were observed in VAD prevalence, with 12153 (22.6%) boys and 10150 (20.0%) girls presenting retinol levels I 0.70 pmoY1 (~2 = 0.11; p= 0.744).
TABLE 2 Proportion of Children with Retinol Levels I 0.70 pmol/l and > 0.70 pmol/l According to Sex % Total Serum--l_.-.-.l retinol I 0.7O_cunoVl > 0.7O~moYl -_.- .._..__._ % _.Serum ..-.__ retinol ._ ..__,,, _,.___,__ 12 77.4 53 41 22.6* 10 40 80.0 50 20.0* 22 21.4 78.6 103 Total __*________,~_______.,,___. __,..._,._, --,* _...I.. L-II”,Y..I ,.,81 “,.-X,__i,-,..*_- _,l_,_E__-l__l___l_ *No Significant Sex Male Female
Freuuencv of zinc deficiencv among deficient serum zinc levels (O/98). The pg%). Children with VAD presented children without VAD presented mean
children with and without VAD: No children showed overall mean serum zinc level was 108.9 pg% (2SD k 43.1 mean zinc levels of 105.1 pg% (2SD ~44.1 pg%) and zinc levels of 110.0 pg% (2SD + 42.3 pg%) (p=O.23 1).
VAD and breast-feeding: With respect to breast-feeding, the groups of children with VAD presented a mean duration of breast-feeding of 6.1 months, while the children without VAD presented a mean of 8.6 months, corresponding to a significant difference (pcO.05) between groups. Freauencv of anemia and/or iron deficiencv among; children with and without VAD: Again no significant differences in frequency of anemia and/or signs of iron deficiency were detected between groups, although anemia was more frequent among children with VAD (Table 3). In the group with VAD we detected 19121 (90.5%) children with signs of anemia and/or iron deficiency, whereas in the group without VAD we detected 49/69 (71.0%) children with these signs (Yates ~2 = 2.33; p = 0.126). The prevalence of anemia and/or signs of iron deficiency was usually elevated in the groups studied. Considering the two groups of children as a whole, 68190 (75.6 %) of them presented some signs of anemia and/or iron deficiency in laboratory tests. Parental educational level and VAD: No significant differences in parental schooling were detected between groups; 11116 (68.7 %) parents of children with VAD and 40/66 (60.6%) parents of children without VAD did not have at least 8 years of study (~2 = 0.36; p= 0.547). Also, no significant difference in maternal schooling was observed between groups; 12/21 (57.1 O/o)mothers of children with VAD and 47/80 (58.7%) mothers of children without VAD did not have at least 8 years of study (x2 = 0.02; p= 0.894). No significant differences were observed when having at least one of the parents with eight or more years of schooling was considered as a
762
I.S. FERRAZ et al.
risk factor, with 12/21 (57.1 %) of the children with VAD and 38/80 (48.7) of the children without VAD not having at least one parent or a person responsible with at least eight years of study (x2 = 0.47; p = 0.494) (Table 3). In general, considering the two groups of children (with and without VAD), we observed that 51/82 (62.2 %) fathers and 59/101 (58.4 %) mothers had not studied for at least 8 years; at the same time we observed that 51/101 (50.5 %) of the children studied did not have at least one parent with at least 8 years of schooling. The general illiteracy rate for fathers and mothers as a whole was 2.2 % (4/182), with 21101 (2.0%) mothers being illiterate. Only 4.9% (g/182) of the fathers and mothers as a whole whose educational level was known succeeded in obtaining higher education.
TABLE 3 Frequency of Some Risk Factors for VAD Among the Children Studied According to Vitamin A Status 1 Risk factor (%) Presence of anemia I at&or iron deficiency Absence of anemia and/or iron deficiency Father with less than 8 yearsof formal education Father with at least 8 years of formal education Mother with less than 8 years of formal education Mother with at least 8 years of formal education Neither parent with at least 8 years of formal education Father and/or mother with at least 8 years of formal education Birth weight < 2.5OOg Birth weight 1 2.500 g N.S. = No Significant.
Children with VAD (%) 19/21 (90.5)* 2121 (9.5) 11/16 (68-V
1Children without VAD (%) 1 Notes (*)N.S 49169 ’’ (71.0)* 20169 (29.0) 40166 (t1N.S. (60.6) t
5116 (31.3)
26166 (39.4)
12121 (57.1X
47180 (58.8) $
9121 (42.9)
33180 (41.2)
12/21 (57.1)#
39180 (48.8) #
9121 (42.9)
41/80 (51.2)
4121 (19,O)f 17/21 (81 .O)
5180 (6,2)& 75180 (93.8)
(S)N.S.
(#)N.S
(E)N.S.
Prematuritv and/or low birth weight and VAD: Although there was no significant difference between groups with respect to low birth weight, a higher proportion of birth weight < 2,500 g was observed in the group of children with VAD (Table 3) with 4121 (19.0%) low birth weight
VITAMIN A DEFICIENCY
IN CHILDREN
763
children in the group with VAD and 5/80 (6.2%) in the group without VAD (exact Fisher test; p = 0.086). As a whole, 9/101 (8.9 %) children were of low birth weight. Per canita income and VAD: Again, no significant differences in annual per capita income was observed between the two groups of children The per capita income of the families of children with VAD was closely similar, but slightly higher, than that of the families of children without VAD, i.e., US% 2,415.60 as opposed to US$2,147.28 (p = 0.222), respectively. Number of household members and VAD: The overall mean number of persons residing in the same household was 4.9 (2SD k 3.63) per domicile. When considered separately, the children with VAD lived in households with 4.7 persons (2SD +_4.03) on average, and the children without VAD lived in households with 4.9 persons (2SD + 3.54) on average, with no significant difference between these values (p=O. 159). Nutritional status and VAD: In the present study, no child (O/94) was classified as wasting or stunting according to NCHS curves.
DISCUSSION Although mean serum retinol levels do not represent vitamin A status at concentrations defined as physiological, it is generally agreed that, under normal conditions, serum retinol levels I 0.70 pmoY1 reflect low hepatic stores of the vitamin (3). Serum retinol was I 0.70 urnoF in 22/103 (21.4%) children, with 1 of these children (1.0%) presenting serum retinol levels below 0.35 pmol/l. This index is above the 20% established as a severe public health problems in communities by the WI-IO (3). Although no child presented xerophthahnia, it is known that even a mild deficiency can increase infant morbidity and mortality rates, especially due to both diarrhea1 and respiratory tract diseases (8, 22), a very important fact in a country where the tiequencies of these diseases are considered to be moderately elevated. These values are lower than those reported by Favaro et al (6) who, in a study of children aged 2 to 8 years in the periurban region of the city, detected 1.8 % of children with retinol levels below 0.30 pmol/l and 48.8% with levels below 0.70 pmoY1; however, in the cited study calorimetric methods rather than HPLC were used for retinol measurement. The results of the present study resemble those reported by GoncalvesCarvalho et al (5), who detected a 17.6% prevalence of serum retinol levels between 0.30 umol/l and 0.70 pmol/l among preschool children living in the slums of the municipality of Campinas (S~O Paul0 State), and are also closely similar to those detected by Rodriguez et al (23) among 12 to 59-month old children in Equador. Outside Latin America, but still in developing countries, Tafesse et al. (24), in a study of Ethiopian children aged 6 months to 6 years, detected a prevalence of 31.9% and 48.9% of serum retinol levels < 0.35 urnoF and ranging from 0.35 to 0.69 umoY1, respectively. The overall mean retinol level was 1.00 umoVl(2SD + 0.77 umoV1) in our study. The age range showing the highest mean serum retinol concentration was that of 12 months of age, with a mean of 1.14 urnoF (2SD ? 0.74 pmol/l), although there was no significant difference between the means for the different age ranges. In addition, these differences may not represent differences in clinical practice since, as mentioned earlier, mean serum retinol levels do not represent vitamin A status at concentrations defined as physiological. Although there are conflicting data about the age range of highest risk for VAD in childhood (3, 25, 26), in our study, 24-month-old children presented the highest prevalence of serum retinol levels I 0.70 umol/l, even though the difference was not statistically significant. A probable explanation for this finding may be the fact that the
764
I.S. FERRAZ et al.
children belonging to this group were under the “protective” effect of breast-feeding to a lesser extent than the other groups, when we consider that breast-feeding proved to protect children from VAD (see discussion below). However, dietary surveys are needed to answer these questions. Despite the controversies, some studies have shown a higher prevalence of VAD in males (9, 27, 28) a fact that was not observed in our study. Mean senmr retinol levels were closely similar for the two sexes: 0.98 pmoY1 for boys and 1.OOpmoY1 for girls (p-0.103); 12/53 (22.6%) boys and lo/50 (20.0%) girls presented serum retinol levels I 0.70 pmoYl(x2 = 0.11; p= 0.744). A significant proportion of the children studied presented signs of anemia and/or iron deficiency [68/90 (75.6%)]. Again no significant differences were observed between the two groups of children with and without VAD with respect to the presence of signs of anemia in peripheral blood and/or iron deficiency. Thus, this indicator was found not to be a risk factor for VAD among the children studied. However, the high prevalence of retinol levels I 0.70 mnoY1 and of anemia and/or iron deficiency show that nutritional deficiencies are not selective in this community, demonstrating that feeding habits must have improved due to improved living conditions ot to educational campaigns, or yet again to supplemental feeding programs, or to all of these factors together. Despite the importance of serum retinol levels I 0.70 pmoYl, and of anemia and/or iron deficiency, in the present study, no child showed serum zinc levels below values considered normal in either group. As observed in animals (15) and also in human beings (16), the trace element zinc plays an important role in RBP synthesis by the liver, so that its deficiency may be a factor for the development of VAD (14). Also, no significant differences in mean serum zinc levels were detected between groups. This observation rules out the possibility of zinc having interfered with the low serum retinol levels in the children with VAD studied here. Several authors have studied the effect of adverse social conditions on the development of VAD (26, 29-31). In the present study we investigated the per capita income - inferred from monthly per capita income - of the families of the children under study as a way to estimate the acquisitive power of this population and to determine whether this factor might affect vitamin A status. The general per capita income was US$2,147.28 per year, corresponding to less than half the Brazilian per capita income in 1997 (US$ 4,743). However, even though this value corresponds to less than half the per capita income for the country, the inequality of income distribution in Brazil is notorious. These children definitely do not belong to the most underprivileged classes in the community, so that the detection of these nutritional deficiencies in the study group becomes even more worrisome. As indicated earlier, the mean number of persons residing in a household usually was 4.9. We thus obtain mean monthly earnings per domicile of US% 876.81. However, further studies are needed for a better economic characterization of our population. The per capita income of the families of children with VAD was slightly higher than that of the families of children without VAD (approximately US$2,415.60 and US$2,147.28 per year, respectively; p = 0.222). Thus, per capita income did not prove to be a risk factor for VAD in the present study, perhaps owing to the relatively reduced number of children studied and also to the absence of wide variation in family income. Because of the relatively small number of children investigated in the present study, these infants are not representative of all children in this age range in the community. Despite the social indicators shown here (per capita income and educational level), at the local level these children belong to the so-called “low” middle class and not to the most underprivileged social classes, a fact that increases the concern about the prevalence of VAD detected. Thus, the present study reveals the occurrence of VAD - even in a subclinical form - among children seen at a puericulture outpatient clinic linked to the local university who were apparently healthy and not
VITAMIN A DEFICIENCY
IN CHILDREN
765
malnourished since no child was classified as wasting or stunting in the present study. This fact has been reported by some investigators (32), showing that the combination of VAD with the absence of wasting or stunting is possible. The mean number of persons per household was similar for both groups. Thus, we cannot state that, in this case, the number of persons in the family represented a risk factor for VAD, although some authors (18,253 1) have reported that children from families with a larger number of persons presented lower retinol levels than children from less numerous families. Although the WHO (3) and some authors have shown a correlation between low educational level and VAD (25, 29, 33), no differences in educational level were found between the parents of the two groups of children in the present study when the mother alone or the father alone was considered, or at least one of the parents, showing that parental educational level is not a risk factor for VAD in this study. Perhaps the lack of significance of this difference was due to the low educational level of the parents in both groups in general, since more than half the children (50.5%) did not have at least one of the parents with more than eight years of schooling. A significant difference was detected between the means for the two groups of children with respect to time of breast-feeding, i.e., the group with VAD (6.1 months) and the group without VAD (8.6 months; ~~0.05). The mean time of breast-feeding for the children with VAD was similar to the values detected by the WHO (34) in economically favored urban populations, in which breast-feeding was rarely offered beyond the sixth month of life, whereas in less favored communities half the mothers still offered their milk to their children at 18 months of age. The group of children without VAD represented a group with an intermediate breast-feeding pattern. Thus, the relatively short time of breast-feeding adopted by economically underprivileged classes witbout the necessary economic and educational support for the acquisition of a diet replacing breast-feeding with foods rich in vitamin A may be one of the factors responsible for the observed VAD, since, as previously observed by others, we noted that breast-feeding seems to “protect” the child against the development of VAD (4, 17-19), since maternal milk contains good concentrations of this vitamin especially during the first postpartum days (20) and in some places it may represent the only dietary source of the vitamin (17, 35). Furthermore, maternal milk, by containing other “anti-infectious” components, reduces the morbidity and impact of infections that induce the loss of vitamin A and increase its requirements by the organism, a fact that may lead to deficiency in children (3). However, further studies on the breast-feeding patterns and the local weaning diets, such as those conducted using alimentary surveys, are necessary for a better elucidation of the real and precise causes of this nutritional deficiency. Prematurity and/or low birth weight also are risk factors for the development of VAD (3), as previously shown by several authors (36-38). The probable explanation for prematurity as a risk factor for VAD is that RBP synthesis by the fetal liver and hepatic deposits of this vitamin occur during the last weeks of pregnancy, as also demonstrated in animals (39), whereas children born at term but with a low birth weight may also have low reserves due to maternal and fetal mahmtrition (3). Although no significant differences were observed between groups, children with VAD tended to have a more frequent history of low birth weight than children without VAD (exact Fisher test: p = 0.086), despite the instruction given to the first group about vitamin supplementation. The study of a larger number of children may indicate a greater importance of the relationship between low birth weight and/or prematurity and the development of VAD. It is known that premature and/or low birth weight children often belong to families of low socioeconomic conditions, a fact that may also influence vitamin a status, although &rther study is needed to test this hypothesis. Furthermore, studies are needed about the efficacy of the dose
I.S. FERRAZ et al.
and parental compliance with the administration of vitamin supplementation to premature and/or low birth weight children, as well as studies of other forms of vitamin supplementation. Final considerations The present study raises various questions still awaiting an answer but shows that the problem of vitamin A deficiency is present in Southeast Brazil and that actions should be taken to combat it, especially by stimulating breast-feeding, providing the opportunity for new investigations in an attempt to explain other factors underlying one more nutritional deficiency among Brazilian children.
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