Vitamin A deficiency and xerophthalmia among school-aged children ...

European Journal of Clinical Nutrition (2004) 58, 1342–1349

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ORIGINAL COMMUNICATION Vitamin A deficiency and xerophthalmia among school-aged children in Southeastern Asia V Singh1 and KP West, Jr1* 1

Center for Human Nutrition, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA

Objective: To determine provisional estimates of the extent of vitamin A (VA) deficiency and xerophthalmia among school-aged children. Design: Literature search of published, unpublished and website-based population survey and study reports, with countryspecific imputation of prevalence rates and numbers of children affected by: (1) VA deficiency based on measured or imputed distributions of serum retinol concentration o0.70 mmol/l (equivalent to o20 mg/dl) and (2) xerophthalmia, by country. Setting: Countries within the WHO South-East Asian Region. Subjects: The target group for estimation was children 5–15 y of age. Interventions: None. Results: The estimated prevalence of VA deficiency is 23.4%, suggesting that there are B83 million VA-deficient school-aged children in the region, of whom 10.9% (9 million, at an overall prevalence of 2.6%) have mild xerophthalmia (night blindness or Bitot’s spot). Potentially blinding corneal xerophthalmia appears to be negligible at this age. Conclusions: VA deficiency, including mild xerophthalmia, appears to affect large numbers of school-aged children in SouthEast Asia. However, nationally representative data on the prevalence, risk factors and health consequences of VA deficiency among school-aged children are lacking within the region and globally, representing a future public health research priority.

European Journal of Clinical Nutrition (2004) 58, 1342–1349. doi:10.1038/sj.ejcn.1601973 Published online 31 March 2004 Keywords: vitamin A deficiency; xerophthalmia; night blindness; Bitot’s spots; school-aged children; South-East Asia

Introduction Vitamin A (VA) deficiency exists as a public health nutrition problem among preschool-aged children in 118 developing countries around the globe, with the South-East Asian Region (defined by WHO to include Bangladesh, Bhutan, India, Indonesia, Democratic People’s Republic of Korea, Maldives, Myanmar, Nepal, Sri Lanka and Thailand) harboring the maximum number of cases (West, 2002). Health consequences of VA deficiency, termed VA deficiency disorders or VADD, early in life include all active clinical

*Correspondence: KP West, Jr, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Center for Human Nutrition, Room W2505, 615 N. Wolfe Street, Baltimore, MD 21205, USA. E-mail: [email protected] Guarantor: KP West Jr. Contributors: VS studied the literature, calculated estimates and wrote the paper. KPW conceptualized the problems, guided the analyses and contributed to writing the paper. Received 18 July 2003; revised 10 November 2003; accepted 1 December 2003; published online 31 March 2004

stages of xerophthalmia including corneal xerophthalmia and its potentially blinding sequelae, impaired mechanisms of host resistance, increased severity of infection, anemia, poor growth and mortality (Sommer & West, 1996). We have previously estimated that, globally, B127 million preschoolaged children under 5 y of age are VA deficient (serum retinol o0.7 mmol/l or having abnormal impression cytology), of whom 4.4 million have xerophthalmia (West, 2002). There are also an estimated 7.2 million pregnant women with VA deficiency (serum retinol o0.7 mmol/l) at any one time in the developing world, of whom B6 million are night blind (West, 2002), a condition attributable to VA deficiency (Christian, 2002). Gestational and postpartum VA deficiency may increase the risk of maternal morbidity (Christian et al, 1998, 2000a) and mortality (West et al, 1999; Christian et al, 200b) and infant mortality (Christian et al, 2001). A high maternal prevalence of low VA status (based on serum retinol o1.05 mmol/l) during pregnancy (eg, 22.0% in Africa and 24.3% in South Asia) (West, 2002), coupled with evidence of recurrent night blindness in repeated pregnancies, suggests

VA deficiency and xerophthalmia among school-aged children V Singh and KP West

1343 that the nutritional problem is likely to be chronic, with antecedent risk possibly starting earlier in childhood and pubescence; that is, 5–15 y of age. However, populationbased data on the prevalence of VA deficiency and the extent and severity of accompanying VADD are lacking for schoolaged children throughout most of the developing world. The original intent of the present study was to estimate the prevalence of VA deficiency and xerophthalmia, and numbers of children affected, between the ages of 5 and 15 y by country and region of the developing world. However, due to scarcity of data at this age for most countries, provisional estimates could only be made for the WHO South-East Asian Region, with merely a few observations possible at this time related to the extent of this problem in sub-Saharan Africa. Still, we hope that resulting provisional estimates for this region will motivate action toward more school-aged assessment of VADD.

Methods We reviewed findings related to xerophthalmia and VA deficiency in school-aged children from published and unpublished and web-based sources. Major sources of data included Multiple Indicator Cluster Surveys (MICS) for enddecade assessment in 55 countries submitted to United Nations Children’s Fund (UNICEF) in the year 2001 (UNICEF, 2001a); survey reports in the Micronutrient Deficiency Information System (MDIS) of the World Health Organization (WHO) in year 1995 (World Health Organization, 1995); summaries of surveys compiled by the Micronutrient Initiative (MI), United Nations Children’s Fund (UNICEF) and Tulane University in year 1998 (The Micronutrient Initiative); and findings of surveys, observational studies and intervention trials reported in the scientific literature. Prevalence data were also obtained from professional society newsletters, periodicals, reports published by governmental and nongovernmental organizations, correspondence with principal investigators and abstracts from International Vitamin A Consultative Group (IVACG) meeting reports over the past 15 y. Wherever possible, prevalence data were abstracted for the relevant age range of this study, 5–15 y. However, prevalence rates covering narrower age ranges (eg, 6–9 y among Thai children (Bloem et al, 1989)) or ranges that only partly included the target group (eg, 13–17 y old among Nepali children (KP West Jr et al, unpublished data, 2003) were assumed to represent the entire target age. Estimates of numbers of children 5–15 y in each country were derived for most countries from two sources: the UNICEF Year 2001 State of the World’s Children Report, which provides estimates of the total population and numbers of preschool children (o5 y) for the year 1999 (UNICEF, 2001b), and the 2001 World Population Data Sheet of the Population Reference Bureau to obtain the percentage of children less than 15 y of age in each country (Population

Reference Bureau, 2001). This percentage was applied to the total population reported by UNICEF to obtain the number of children o15 y, from which was deducted the number o5 y to estimate the number of children 5–15 y in each country. This latter number served as the number at-risk against which prevalence estimates were multiplied to obtain numbers of VA-deficient and xerophthalmic children. Reports on the prevalence of VA deficiency were based on biochemical and cytological indicators. VA-deficient status was primarily defined as a serum (or plasma) retinol concentration o0.70 mmol/l (o20 mg/dl) (IVACG, 1993). If serological data were reported only as a mean concentration with standard deviation (s.d.), or standard error with sample size, a prevalence rate was calculated under an assumption of normality of serum retinol concentration, as frequently observed in population reports (West, 2002; Ballew et al, 2001). This allowed us to derive a standard normal deviate (Z-score) from a reported mean and s.d. The probability associated with the area under the left tail of the distribution, below the cut-point of 0.70 mmol/l, was adopted as an estimate of prevalence of deficiency, as previously carried out for preschoolers (West, 2002). In one country, the prevalence of abnormal conjunctival impression cytology, a comparable population indicator of VA deficiency (Natadisastra et al, 1988; Reddy et al, 1989; Sommer, 1995), was also used from one study for modeling an estimate of VA deficiency for school-aged children (ie, Indonesia) (Natadisastra et al, 1988). Estimation of the prevalence of xerophthalmia and consequent numbers of school-aged cases was based on reports of WHO-defined clinical stages of night blindness (XN), Bitot’s spot (XlB) and active corneal disease (X2 and X3) (Sommer, 1995; Sommer & West, 1996). Conjunctival xerosis (XlA) was not used as a clinical indicator due to unreliability of diagnosis (Sommer, 1995). A single prevalence of ‘active xerophthalmia’ was calculated as done previously for preschool children (World Health Organization, 1995; The Micronutrient Initiative, 1998; West, 2002). Thus, aggregate prevalences were adopted as reported. Where only ‘stage-specific’ rates were reported, an aggregate rate was calculated by summing rates of X3, X2, XlB and half of the reported rate of XN, under a conservative assumption that half of the children reported as having night blindness also had Bitot’s spots, as assumed in previous estimates for preschoolers (West, 2002). When only one eye sign was reported, we assumed that other ocular manifestations of xerophthalmia were absent (West, 2002).

Estimation of prevalence and numbers affected in the South-East Asian region Although relevant data were most widely available in SouthEast Asia, studies of school age VA status remain sparse, and vary considerably in design and representativeness. Such diversity of evidence led us to adopt country-specific European Journal of Clinical Nutrition


1344 approaches to impute the prevalence of VA deficiency and xerophthalmia in an attempt to optimize the use of available data. Bangladesh. No rural serological data on VA status were available for children 5–15 y of age. However, data on biochemical VA deficiency were available from four urban/ periurban studies. An unweighted mean prevalence of 21.2% was computed from serum retinol concentrations from two studies of nonschool-attending adolescent female garment factory workers in Dhaka (Ahmed et al, 1997, 2001). Given that more than 90% of urban adolescents throughout the country do not attend school (Bangladesh Bureau of Statistics, 1999), a weight of 0.9 was assigned to this estimate. An unweighted mean prevalence rate of 3.5% was also calculated from two studies of school-attending adolescent children in Dhaka (Ahmed et al, 1996, 1998). As less than 10% of urban children attend school (Bangladesh Bureau of Statistics, 1999), a weight of 0.1 was assigned to this estimate. The weighted percentages were summed to obtain an urban prevalence of 19.4%. Two further assumptions were made to scale this percentage up to a provisional national estimate: (a) Since all four studies were in girls, males were assumed to have a prevalence of VA deficiency comparable to females, based on data suggesting males to be as or more VA deficient than females in the preschool years (Sommer & West, 1996). This allowed the above percentage to be applied to school-aged boys. (b) The urban:rural prevalence ratio for VA deficiency was assumed to be 1.0 based on an observed national rural:urban prevalence ratio of B1.0 for the clinical symptom of XN (UNICEF, 1998). Based on this apparent comparability in risk, a provisional prevalence of 19.4% was applied to the school-aged children throughout the country. For xerophthalmia, a national prevalence of 3.7% for night blindness (UNICEF, 1998), among children 6–11 y of age, was applied to the entire 5- to 15-y-old population. As a conservative measure, we assumed that other clinical stages of xerophthalmia were either solely exhibited by children with night blindness or absent in the population. Bhutan. No VA status data were available for school-aged children. However, data from a 1985 national survey, as summarized in the WHO MDIS in 1995 (World Health Organization, 1995), indicated that 14% of Bhutanese children 0–4 y had a serum retinol concentration o10 mg/dl (o0.35 mmol/l). Under an assumption of normality and an associated s.d. ¼ 9.3 mg/dl, this percentage would suggest a prevalence close to 50% o20 mg/dl. Rather, the prevalence of 14% o10 mg/dl among preschoolers was doubled to 28%, despite the lack of VA programs for this older group, in order to impute a conservative prevalence of VA deficiency (o20 mg/dl) for children 5–15 y of age. A national prevalence of xerophthalmia among 6–12 y Bhutanese children was reported in 1976 to be 1.3% (Tilden, European Journal of Clinical Nutrition

1986; Task Force for Child Survival and Development, 1991). Given the age and poor description of methods associated with this survey, the prevalence was down-weighted by 0.5 to yield a conservative prevalence estimate of 0.65%. Democratic People’s Republic of Korea. There was no estimate available in the literature on VA deficiency in North Korea. Although likely to exist as a result of famine during the past 5 y, in the absence of data no prevalence for either VA deficiency or xerophthalmia was estimated for North Korea, leaving the North Korean child population to be excluded from the WHO regional denominator. India. Population-based serum retinol data among schoolaged children are lacking in India. Three (Pant & Gopaldas, 1987; Pratinidhi et al, 1987; Reddy et al, 1989) biochemical studies, among schoolers living in high-risk, urban slums yielded an unweighted estimate of 69.3% for children with serum retinol concentrations o0.70 mmol/l. In the absence of other data, a weight of 0.3 was arbitrarily applied to this value in an attempt to account for both uncertainty and lack of representativeness. The resulting prevalence of 23.1% was applied to the school-aged population of the country. This provisional estimate seems reasonably conservative given widespread reports of poor diet (Pratinidhi et al, 1987; Ramakrishnan et al, 1999), persistent xerophthalmia (Khandait et al, 1999) and undernutrition (Pratinidhi et al, 1987; Department of Women and Child Development, 1998) amidst a lack of any VA deficiency prevention programs for school-aged children throughout India. For xerophthalmia, national, population-based data on XN were available for Indian children 5–14 y of age based on UNICEF Multiple Indicator Cluster Surveys (MICS) carried out in recent years in each state (Department of Women and Child Development, 1998). Prevalence rates of mild X1B for eight states were also available from the National Nutrition Monitoring Bureau (2000) and from five other survey reports in four states (Rahmathullah et al, 1990; Gupta et al, 1998; Aravind Comprehensive Eye Survey, 1999; Nambiar & Kosambia, 2003; Singh & Sharma, 2003) covering children whose ages ranged from 5 to 16 y (Rahmathullah et al, 1990; Gupta et al, 1998; Aravind Comprehensive Eye Survey, 1999; Nambiar & Kosambia, 2003; Singh & Sharma, 2003). As these latter rates were not considered to be statewide, they were weighted by a factor of 0.75, to account for the lack of representativeness, and averaged with each statewide MICS prevalence rate for XN. Rates for all states were summed and averaged (unweighted) to obtain a national prevalence for India (2.8%), which was then multiplied by the estimated number of school-aged children in the country. Indonesia. We could locate no data on serum retinol levels among school-aged Indonesian children. However, serum retinol concentration data do exist from three studies of preschool-aged children and five studies of pregnant and


1345 lactating women in Indonesia. These data provided an opportunity to interpolate a prevalence rate for the 5- to 15-y-old age group, at the mid-interval age of 10 y, by entering age-specific prevalence rates from the above eight studies into a least-squares linear regression model. The resulting equation was: Y ¼ 49.42–1.52X, where Y is the estimated prevalence of VA deficiency (serum retinol o0.70 mmol/l) per 100 and X is the age in y. Given prevalences of 58.4, 39.4 and 35.6% at average ages of 2.4, 2.5 and 4.5 y among preschoolers (Natadisastra et al, 1988; Kjolhede et al, 1995; Muhilal, 1995), and 10.4–17.0% among pregnant and lactating women of ages 15–40 y (Stoltzfus et al, 1992, 1993; Suharno et al, 1993; Muhilal, 1995; Tanumihardjo et al, 1996), we estimated a prevalence among 10-yold children of 34.2%, which was applied to the combinedsex population of 5- to 15-y-old children in Indonesia. No prevalence data could be located on xerophthalmia in school-aged Indonesian children. Thus, a xerophthalmia prevalence of 0.4% among preschoolers from a national survey in 1992 (Muhilal et al, 1994) was adopted for schoolers. This estimate is likely to be conservative, given a well-known trend for the prevalence of mild xerophthalmia to rise with age at least into the early school years (Sommer, 1982; Djunaedi et al, 1988; Muhilal et al, 1994), a lack of any VA supplementation program for this age group, and probably adverse nutritional effects from a national economic crises during the past decade. Maldives. No report of VA status exists in this country, leading to its exclusion from present regional estimates of VA deficiency and xerophthalmia. Myanmar. A mean, unweighted VA deficiency prevalence of 27.5%, based on serum retinol values o0.70 mmol/l, among 2- to 14-y-old children in three surveyed districts reported in 1989 (Sunn et al, 1989) was still considered to be a valid estimate for school-aged children in the country. For xerophthalmia, a prevalence rate of 4.04% obtained for XlB in a population-based survey of 6–14 y children in four regions as reported in 1989 (Thein & Myint, 1989) was also considered valid for the present exercise. Other stages of xerophthalmia were not reported and inferred, conservatively, to be absent. Nepal. In Nepal, amidst lack of nationally representative biochemical data on VA deficiency in school-aged Nepalese children, unpublished baseline or control group serum retinol data were available in 1992 first trimester pregnant girls 14–17 y of age living in the southern plains of the country and participating in two maternal supplementation trials (KP West Jr and P Christian, unpublished data, 2003). The resulting prevalence of 14.2% o0.70 mmol/l was unlikely to have been affected by plasma expansion because it was based on phlebotomy in the first trimester of pregnancy. The value is lower than values obtained during a 1998 national

survey of 19.8% in a stratum of 41 women o20 y of age and 23.7% in a stratum of 122 4-y-old children of both sexes (Nepal Micronutrient Status Survey, 1998). Based on assumptions of uniform risk across earlier school-aged years and gender, as observed in the national sample (Nepal Micronutrient Status Survey, 1998), a prevalence of 14.2% was applied to the Nepalese school-aged population. The xerophthalmia rate for school-aged children was obtained from a 1998 national survey of XN and XlB (Nepal Micronutrient Status Survey, 1998). An aggregate prevalence for all active stages of xerophthalmia was not reported; therefore, assuming that half of the children with XN also had XlB (Sommer, 1982), an aggregate prevalence of 2.6% was obtained by adding half of the prevalence rate of XN (0.5 1.33%) to that of XlB (1.91%). Sri Lanka. No data were found on VA deficiency in children 5–15 y of age in Sri Lanka, forcing our estimate to be derived from a 1979 national survey prevalence of 6.0% among 4- to 6-y-old children (Brink et al, 1979). Under assumptions of little improvement in general socioeconomic, health and nutritional status in Sri Lanka, as reflected by a relatively constant infant mortality rate over the past two decades (United Nation’s Development Programme, 1999), coupled with what appeared to have been a general lack of VA programming activity during this time period, a VA deficiency prevalence estimate of 6% among children 4– 6 y of age dating to 1979 (Brink et al, 1979) was applied to the 5–15 y age range. Similarly, 1979 data on the prevalence of XN (1.4%) and XlB (2.1%) (Brink et al, 1979) were used to estimate the present burden of xerophthalmia in schoolers. To obtain a single estimate for xerophthalmia, half of the XN prevalence rate was added to that of XlB, under an assumption that half of the children reporting to have had XN also had XlB and thus were included in the X1B rate. Thailand. The northeastern region of Thailand historically represents the only major locus of undernutrition with VA deficiency in the country. An unweighted mean prevalence for VA deficiency of 41.83% was obtained from two surveys of children aged 6–9 y and 1–8 y undertaken in Northeastern Thailand between 1985 and 1990 (Bloem et al, 1989, 1990). This prevalence was down-weighted by two factors: (a) As Northeastern Thailand was assumed to represent only 25% of the country, a weight of 0.25 was applied to this prevalence. (b) Since the prevalence was assumed to have been measured during the high-risk dry part of the year, an additional weight of 0.5 was also applied to account for seasonal variation. These adjustments led us to estimate a school-aged VA deficiency prevalence of 5.2%. In order to estimate a single prevalence of xerophthalmia where both XN and X1B had been reported (Bloem et al, 1989), half of the XN prevalence rate was added to XlB, under the assumption that half of the children reported as having European Journal of Clinical Nutrition


1346 night blindness also had Bitot’s spots, as assumed previously (West, 2002). To account for the lack of national representation, this value was down-weighted by a factor of 0.25. An additional weight of 0.5 was applied to the estimate to account for seasonal variation as the data appeared to apply only to the higher risk dry season. These adjustments rendered a national xerophthalmia prevalence of 0.15%, which was applied to the 5- to 15-y-old population of the country.

Results Provisional estimates of the prevalence of VA deficiency and numbers of affected children between 5 and 15 y of age for each country in the WHO South-East Asian Region are shown in Table 1. The overall prevalence estimate for VA deficiency is 23.4%, with individual country estimates ranging from a low of 5.2% in Thailand to a high of 34.2% in Indonesia. This overall prevalence leads to an estimate of B82.7 m VA-deficient school-aged children in the region. While not having the highest apparent prevalence (23.1%), India has the largest number of VA-deficient schoolers, estimated at 56.4 m, representing 68% of all deficient children at this age in the region. If one were to apply the minimum VA deficiency prevalence of 15%, as recently revised by the IVACG (Sommer & Davidson, 2002) for determining public health significance in preschoolers, the countries of Bangladesh, Bhutan, India, Indonesia and Myanmar would appear to have a VA deficiency problem of public health importance among school-aged children. Table 1 also displays provisional estimates of the prevalence and numbers of cases of mild xerophthalmia (XN and X1B) between 5 and 15 y of age for each country in the WHO South-East Asian Region. At an imputed overall prevalence of 2.6%, there are B9.0 m children with night blindness and/or Bitot’s spots in the Region. The maximum prevalence

appears to be in Bangladesh (3.7%); the minimum prevalence is in Thailand (0.15%). As with VA deficiency, due to a substantial estimated prevalence (2.8%) combined with its large population size, the largest number of school-aged children with xerophthalmia lives in India (B6.8 m), representing B76% of all cases throughout the Region. Countries of Bangladesh, India, Myanmar, Nepal and Sri Lanka exceed a minimum prevalence criterion of 1.5% for all active stages of xerophthalmia, a minimum public health criterion that has been recently proposed for preschool-aged children (West, 2002). Figure 1 displays a map of the joint distribution of prevalences of VA deficiency above or below 15% and xerophthalmia above or below 1.5% in each country of the Region, as recently reported for preschool children throughout the world (West, 2002). Countries with the darkest shade that, based on this exercise, appear to exceed both cutoffs are Bangladesh, India and Myanmar. Nepal is on the borderline between the highest and second highest risk classification.

Discussion Although there exists substantial documentation of prevalence, severity and health consequences of VA deficiency in preschool-aged children (Sommer & West, 1996), and rapidly emerging evidence about this nutritional problem in pregnant and lactating women (West, 2002), little has been done to evaluate systematically the extent of VA deficiency in the preadolescent and adolescent years. Underlying the current global emphasis on preschoolers and pregnant women are the multiple, known health disorders of VA deficiency and the urgent and continuing need to launch, expand and sustain preventive efforts in these high-risk groups (Sommer & West, 1996; Christian et al, 1998; Christian et al, 2000a, b; Christian, 2002). In contrast, preadolescent school-aged individuals, as a demographic

Table 1 Prevalence of VA deficiency and xerophthalmia among school-aged children (5–15 y) with estimated numbers of cases in the WHO South-East Asian Regiona VADb South/South-East Asia

Xerophthalmia

Population, 5–15 y

Percentage (%)

Number

Percentage (%)

Number

Bangladesh Bhutan India Indonesia Myanmar Nepal Sri Lanka Thailand

35 658 800 527 880 244 324 160 42 863 050 10 643 470 6 102 850 3 621 920 9 774 440

19.4 28.0 23.1 34.2 27.5 14.2 6.0 5.2

6 917 807 147 806 56 438 881 14 659 163 2 926 954 866 605 217 315 508 271

3.7 0.7 2.8 0.4 4.0 2.6 2.8 0.2

1 319 376 3695 6 841 076 171 452 425 739 158 674 101 414 14 662

Total

353 516 570

23.4

82 682 802

2.6

9 036 088

a

Countries in the WHO South-East Asian region excluded in the above table are Democratic People’s Republic of Korea and Maldives, due to a lack of prevalence data on VA deficiency and xerophthalmia among school-aged children. b Based on measured or imputed serum retinol concentration o0.7 mmol/l (Sommer, 1995).

European Journal of Clinical Nutrition


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Figure 1 Countries in the WHO South-East Region stratified by joint prevalence of VAD, defined by serum retinol concentration o0.7 mmol/l and/or xerophthalmia (X), all active stages combined, among children 5–15 y of age.

group, are widely regarded as having relatively lower health and nutritional risks. This lower risk profile has likely depressed motivation historically to assess the prevalence of VA deficiency and its disorders or to implement VA deficiency prevention programs in school-aged children. Indeed, the public health consequences of periadolescent VA deficiency, other than mild manifestations of xerophthalmia, remain largely unknown. While blinding xerophthalmia seems to be exceedingly rare, other less apparent or specific health consequences of VA deficiency known to exist in younger children, such as increased severity of diarrhea (Sommer & West, 1996), could contribute to the burden of disease in this age group and should not be assumed to be absent. Furthermore, beyond plausible risk of comorbidity, given that maternal night blindness recurs with repeated pregnancy during the reproductive years in high-risk populations (Katz et al, 1995), it is possible that adolescent VA deficiency antecedes and predicts chronic maternal VA deficiency and its apparent health consequences (Christian et al, 1998, 2000a, b, 2001; West et al, 1999). This latter possibility would confer far greater importance to the need to quantify the prevalence and severity, and understand the epidemiology of VA deficiency in early adolescence.

In this report, we provide provisional estimates of the prevalence of VA deficiency and xerophthalmia, and the numbers affected, among children 5–15 years of age in the WHO South-East Asian Region. After reviewing the literature, this was the only region of the world for which we could locate a minimum set of published and unpublished population data on the problem at this age from which such estimates could be made. The exercise suggests that at least one-quarter of all school-aged children, or nearly 83 million in the region are VA deficient, defined as having a serum retinol concentration below 0.70 mmol/l (20 mg/dl). We further estimate that 10.9%, or 9 million, of deficient children have mild xerophthalmia (night blindness or Bitot’s spots), equivalent to an overall prevalence of 2.6%. Unknown in this estimate is the population of potentially unresponsive Bitot’s spot cases as has been reported in some populations of preschool children (Emran & Tjakrasudjatma, 1980; Semba et al, 1990). Interestingly, both prevalence estimates for VA deficiency and xerophthalmia exceed public health minima of 15% and 1.5%, respectively (Sommer & Davidson, 2002; Ross, 2002; West, 2002), as established by the WHO and the International Vitamin A Consultative Group (IVACG) for identifying VA deficiency as a public health problem in preschool-aged children. We propose that, European Journal of Clinical Nutrition


1348 until modification is warranted, these cutoffs also be considered applicable to children 5–15 y of age. Although very few data were available to estimate the prevalence or burden of school-aged VA deficiency in other regions of the world, population surveys or communitybased studies carried out in the Cameroon (Gouado et al, 1996), Ethiopia (Kassaye et al, 2001), Ghana (Ghana VAST Study Team, et al, 1993), Malawi (Brabin et al, 1999), Senegal (Carlier et al, 1993) and Tanzania (Ash et al, 2003) over the past decade have revealed prevalences of 0.5–6% for xerophthalmia and 13–60% for VA deficiency (o0.70 mmol/ l). Recently, a prevalence of 34% was reported among schoolattending adolescents in Nigeria (Ene-Obong et al, 2003). These ranges suggest that VA deficiency could be a significant public health problem, while raising the need for more representative population data, throughout subSaharan Africa. These provisional estimates suggest that school-aged VA deficiency could be an important public health problem in the South-East Asian region due to the numbers of children likely affected, the potential for associated but largely ignored (and unknown) health consequences at this age and because of the potential for deficiency in early adolescence to predispose women to chronic VADD during the reproductive years, especially during and following pregnancy.

Acknowledgements We thank Parul Christian for sharing early, unpublished tables on vitamin A deficiency in India. This study was funded by Cooperative Agreement No. HRN-A-00-97-0001500 between the Office of Health and Nutrition, US Agency for International Development (USAID), Washington, DC, USA and the Center for Human Nutrition, Department of International Health, The Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA with additional support from The Bill and Melinda Gates Foundation, Seattle, WA, USA and the Sight and Life Research Institute, Baltimore, MD, USA.

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