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From Eveleth PB (1986) Population Differences in Growth: Environmental and Genetic Factors. In Human Growth: A Comprehensive Treatise. Faulkner F and Tanner JM (eds.) Methodology, Ecological, Genetic, and Nutritional Effect on Growth. vol. 3, New York: Plenum Press, pp. 221-239.

From Eveleth PB (1986) Population Differences in Growth: Environmental and Genetic Factors. In Human Growth: A Comprehensive Treatise. Faulkner F and Tanner JM (eds.) Methodology, Ecological, Genetic, and Nutritional Effect on Growth. vol. 3, New York: Plenum Press, pp. 221-239.

differential reflects the size of the mothers; women are often smaller in poorer families. However, differences in birth weight also reflect what Hytten calls a ''comprehensive pattern of deprivation'': a poorer quality diet, low pregnancy weight gain, mothers being underweight at conception, the absence of or poor quality prenatal care, poor housing, and behaviors such as smoking and alcohol and drug use.

Height in children and adults is positively associated with socio-economic status throughout the world. Figure 4 shows the range of boys' heights from richer and poorer families in a number of countries. Social class differences in boys' heights varied from very little in Scandinavia to approximately 12 cm in the Indian samples. A number of studies have shown that when indicators of social position are expressed on a continuous or graded scale, the relationship with height is monotonic; that is, height increases with an increase in social position. This observation appears to be true even between groups from quite narrowly defined social strata, as shown by data from a single slum in Bangladesh (Table 6). A number of in-depth studies in developing countries of the relationship between socio-economic status and height of children have consistently shown height to be responsive to individual socio-economic indicators, whether of asset wealth or income, or proxy indicators, such as land-holding, grain yields, parental education, or occupation (Table 7).

A similar relationship can be shown in developed countries. For example, in the US National Health and Examination Survey, child height increased monotonically in relation to increments in both household income and parental education (the data were controlled for race). In Britain, the National Child Health and Development Study showed that the difference in height at age 7 between children born in social classes I and II and those in V averaged 3.3 cm; at age 16, the difference was 4.4 cm, in both instances controlling for confounding variables.

In recent years, social class gradients in height, weight, and age of peak height velocity and menarche have begun to attenuate in a few wealthy countries (Sweden, Norway, Finland, and Hong Kong). This seems to be because secular trends in growth have been faster among the lower than higher social class children, and it probably indicates general high living standards rather than growth in a 'classless' society.

Social class gradients in attained adult height are also well documented. In British adults, and Swedes born up to the mid-1950s, average height of manual and nonmanual classes differs by approximately 3 cm for men and 2 cm for women. These averages may mask the effects of upward mobility: Those who move up a class tend to be taller than those who stay within the same social class. In both Swedish and British populations, attained adult height has been shown to be related to economic conditions during childhood, independent of parental height and birth weight. Environmental influences exhibit an inter- as well as intragenerational effect on attained adult height. They also manifest in health outcomes as described previously: Social conditions contribute to nutritional deficiency in early childhood that results in delayed linear growth (indexed by shorter leg length), and this is associated with increased mortality risk for coronary heart disease in later life.

Table 6 Adult and child anthropometric status by livelihood group in a Bangladeshi slum

Variable

Landlords/ traders

Petty traders

Laborers (male labor)

Laborers (female/ child labor)

Statistical significance (p)

Children <5 years n 50

Weight/age as % of NCHS median, 77.9 (9.8) mean (SD)

Height/age as % of NCHS median, 91.4 (3.8) mean (SD)

BMI, mean (SD) 20.4 (2.4) Adults—nonpregnant women n 31

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