Risk Factors for Vitamin A Deficiency

Vitamin A deficiency is more common among poor families in developing countries, and along with poverty are many associated risk factors such as low maternal and paternal education, lack of land, crowding, poor hygiene, increased infectious disease morbidity, geographic isolation, lack of a home garden, and inadequate intake of vitamin A. Infants, preschool, and primary school-aged children are at higher risk for vitamin A deficiency,

Fig. 17. Risk factors for vitamin A deficiency.

and boys are affected more often than girls. Breast-feeding practices such as no breastfeeding, early weaning, or rapid weaning are associated with an increased risk of vitamin A deficiency. Pregnant women and nonpregnant women of childbearing age are at higher risk of vitamin A deficiency. Vitamin A deficiency tends to cluster in households and in villages, with higher risk of xerophthalmia among children within the same family, and within mothers and their children. The relationships of risk factors for vitamin A deficiency are shown in Fig. 17.

5.3.1. Poverty

In developing countries, low socioeconomic status is a strong risk factor for vitamin A deficiency, as many families living in poverty cannot afford vitamin A-rich sources of animal foods such as eggs and meat and may have lower consumption of plant sources of vitamin A. However, the effects of poverty extend beyond food availability and quality of the diet. Poverty is also associated with lower quality of housing, lack of running water, poor sanitation, crowding, and an increased burden of infectious diseases. A poor level of education (see Subheading 5.3.2.), lower income, lack of land, and no home garden (see Subheading 5.3.9.) are part of the general complex of poverty. These factors together may increase the burden of infectious diseases and its associated morbidity, and infectious diseases such as diarrheal disease and measles are well known risk factors that may precipitate xerophthalmia (see Subheading 5.3.6.).

Early studies in Copenhagen showed that xerophthalmia was more common in children who came from poor families (49). Investigations in Indonesia conducted in the 1930s and later have shown an association between poverty and xerophthalmia (115,741). Vitamin A intake and dark adaptation testing were worse among the poorest families in a study of families in Pennsylvania conducted in the late 1930s (742). In a country-wide survey in Indonesia in the late 1970s, principal bathing facility and principal occupation of the head of the household were associated with an increased risk of xerophthalmia (285). In the 1982-1983 Bangladesh nutrition survey of vitamin A deficiency that involved 11,618 rural households and 18,660 preschool children, the risk of xerophthalmia was associated with several indicators of low socioeconomic status, including not having a garden or a tin roof on the house (743). Households without a wristwatch, radio, or bicycle had a 1.5-3.2 greater risk of having a child with xerophthalmia. Nearly 80% of blind children came from landless households (743). In Malawi, xerophthalmia was more common in families where the head of the household was a farmer or fisherman compared with a tradesman or merchant (673). Low socioeconomic status, as reflected by an unprotected water source, no private latrine, and bamboo walls of the house, was associated with xerophthalmia among households in Indonesia (744).

In a study of 29,615 children, aged 6-72 mo, in northern Sudan, lack of water piped into the compound and relative poverty (as determined by the household dwelling, family possessions, and personal appearance of family members) were associated with an increased risk of xerophthalmia (647). In a case-control study from Nepal, the risk of xerophthalmia in children was inversely associated with household socioeconomic conditions (745). A thatched roof (odds ratio [OR] 3.25, 95% confidence interval [CI] 2.00-5.29), lack of an upper story of the house (OR 5.92, 95% CI 2.97-11.81), and lesser ownership of a radio (OR 2.52, 95% CI 1.34-4.75), a watch (OR 1.75, 95% CI 1.02-3.01), cattle (OR 2.12, 95% CI 1.35-3.32), or goats (OR 1.59, 95% CI 1.06-2.36) was associated with xerophthalmia (745). In a population-based study of 5352 children, aged 0-5 yr, in Cameroon, risk factors for xerophthalmia included a roof made of leaf or straw (OR 3.97, 95% CI 2.00-7.88), an indicator of low economic status (746).

Xerophthalmia has been associated with larger household size in Indonesia (285) and larger family size in urban Bangladesh (747), but no relationship was found between xerophthalmia and household size in Malawi (673). In Bangladesh, a family size of three or more children compared to one or two children was associated with an increased risk of xerophthalmia (OR 3.2, 95% CI 1.61-6.50) (748). Larger overall fluctuations in poverty may account for changes in the incidence of xerophthalmia over time. In Egypt between 1912 and 1931, the incidence of xerophthalmia in government ophthalmic hospitals peaked in 1913 and in 1918-1919, the former peak coinciding with economic crisis in Egypt and the latter peak coincided with poor conditions in the country at the end of World War I (749).

5.3.2. Education

A low level of education for the mother, father, or both, appears to be a strong risk factor for xerophthalmia among children. In Bangladesh, maternal education was an independent risk factor for xerophthalmia in her child, after adjusting for occupation of the head of the household, landholding, and other potential confounders (743). The relative risk for a child to have xerophthalmia if the mother had no schooling compared to at least 6 yr of schooling was about three (743). In Malawi, the risk of a household having a child with xerophthalmia was higher if the head of the household had no formal schooling compared with any formal education (OR 1.38, 95% CI 1.05-1.82) (673). A maternal education level of less than 6 yr was associated with xerophthalmia among households in Indonesia (744). In northern Sudan, literacy of the mother, father, or both was protective against xerophthalmia (647). A level of maternal education less than 9 yr was associated with vitamin A deficiency in rural Mindanao in the Philippines (636). Maternal literacy was associated with lower risk of xerophthalmia in her child (OR 0.10, 95% CI 0.01-0.76) in Nepal (745).

5.3.3. Geographic Location

Xerophthalmia has been described in more isolated, difficult-to-reach villages and households in developing countries. It is more common in rural than urban settings, although xerophthalmia may be found in some slum areas of large cities. A large distance from the house to the nearest road of >20 kilometers was a risk factor for xerophthalmia (OR 2.64, 95% CI 1.06-6.57) among preschool children in Cameroon (746). Among nonpregnant women of childbearing age in Cambodia, the prevalence of night blindness was higher in the more isolated rural provinces of Rattanakiri and Otar Meanchey (603).

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