There are studies that look at the effect of infectious diseases during early childhood has on growth (Martorell et al., 1975;Black et al., 1982; Rowland et al., 1988; Moore et al., 2001). The results from these studies conclude that exposure to pathogens (esp. those resulting in diarrhoea) during the early stages of life increase the likelihood of linear growth faltering.
Diarrhoea and pneumonia are two major components of disease burden in children of developing nations. Diarrhoea is a widespread result of infections common throughout developing nations according to the World Health Organization (WHO, April 2013). The spread of diarrhoea is most often through contaminated water and food, and also from person to person as a result of poor hygiene. The high prevalence of diseases like pneumonia and diarrhoea in developing countries is a result insufficient access to clean water, absence of adequate waste disposal, and poor primary health care (Ribeiro, 2000; WHO, April 2013). Studies show that both diarrhoea and pneumonia may result in slower growth (Rowland et al., 1988; Moore et al., 2001; Checkley et al., 2002). Moore et al., (2001) did a longitudinal study in a town in Northeast Brazil, analysing the effect of childhood infection in the first two years of life on growth from age 2-7 years. Results from this study showed that an increasing difference among children in episodes of infections during the first two years resulted in an increasing difference in their growth outcomes.
A study by Biritwum et al. (1986) on growth of rural Ghanaian children under five years of age further demonstrates the greater impact of disease during the first two years. Results from this study suggested that children ranging in age from seven months to 12 months had the highest incidence of diarrhoea. Checkley et al, (2002) found diarrhoea during the first 6 months was a significant determinant of growth retardation. It has been suggested that diarrhoea impacts this age range more due to the introduction of weaning foods (Cameron, 1991). The age when weaning foods are introduced, the type of weaning foods introduced and whether or not they are sanitary are all important. These are associated with mothers’ knowledge about the benefits of appropriate practises related to weaning foods. A study by Ashworth and Feachem (1985) reviewed data from 12 developing countries that assessed the importance of weaning education to improve the health of infants. Results from this review suggested that weaning education improved the nutrition status of the infants. Weaning education allowed women to make decisions about the type of supplementary foods to introduce, when to introduce them and how to reduce the contamination of weaning foods by following hygiene practices.
Height as a biomarker of early life conditions
Height has been recognised as a biomarker for centuries. Boas was among the first to actively use height as a biomarker of early life conditions. There are several studies that analyse the effect that changing developmental circumstances, broadly characterised, have on final growth outcomes of individuals (e.g. Boas, 1912; Ito, 1942; Greulich, 1957; Froehlich, 1970; Smith et al., 2003). These studies argue that changes in developmental circumstances as a result of migration resulted in an increase in overall height. As an example, the study by Froehlich (1970) on Japanese migrants in Hawaii who were all from Hiroshima prefecture. This study finds that there is a 10.6 cm increase in mean height between the first generation of men born in Hawaii as compared to those who were born in Japan. The difference between women who migrated to Hawaii and those who were born there is smaller (mean Δ = 4.2 cm). Though this study is comparing related individuals there is no direct measure of changes in early circumstances leading to differences. The author notes several limitations, but suggests these limitations are not affecting the results. One of these major limitations is aging effects, as the males and females who were born in Japan have mean ages of 79.5 and 70.3 years, respectively. Those in the 2nd generation born in Hawaii were 43.5 years for males and 50.6 years for females. Though the author provides support for the position that age is not influencing the interpretation a great deal, the age differences in these groups still bias outcomes, more for the difference between the males than for their female counterparts. The importance of age will be further discussed.
Based on the results from this study and other studies examining the relationship between environmental conditions and height, a generalised claim can be made about inferred improvements in environmental conditions, likely during the first few years of post-natal life, typically resulting in increases in mean height.
Leg length as a biomarker of early life conditions
The idea that leg length might be a better indicator of developmental circumstances was first proposed by Leitch in 1951. He argued that children experiencing better developmental circumstances associated with their family’s higher socioeconomic status will have both absolutely and relatively longer legs. Occupying a higher socioeconomic status commonly results in better nutrition and better health generally. His argument was based on the cephalocaudal gradient of growth proportions of the human body (Figure 2.4.1). During infancy, from about six months of age through to puberty, legs grow faster than the trunk (Gasser et al., 1991) (Figure 2.4.2), hence any disturbance due to lack of nutrition combined with exposure to pathogens arguably increases the likelihood of permanent stunting disproportionately in leg length (Bogin and Varela-Silva, 2010).
Chapter 1: Introduction.
1.1 Theoretical frameworks.
1.2: Thesis organisation
Chapter 2: Literature Review
2.1: Infancy, childhood, and risks of permanent stunting
2.2: Factors affecting growth and development
2.3: Height as a biomarker of early life conditions
2.4: Leg length as a biomarker of early life conditions
2.5: Possible impacts on interpretations of differences in research designs and differences in how developmental environments are characterised
2.6: Linear Enamel Hypoplasia as a marker of stressful episodes during childhood
Chapter 3: Participants and Methods
3.1: The Punjab: Background information related to participating families
3.2: Recruitment and study participants:
3.4: Analysis of the extent of stress and development outcomes
3.5: Analysis of the timing of stress and development outcome
3.6: Intergenerational analysis
Chapter 4: Results
4.1: A Description of Participating Families
4.2: Anthropometric Description of Families.
4.3: Descriptive Analysis –Linear Enamel Hypoplasia
4.4: Interpretation of anthropometric measures in relation to early developmental conditions within each generation
4.5: Relationship between presence or absence of LEH and anthropometric measures
4.6: Relationship between early and repeated stress events and anthropometric measures.
4.7: Tests of hypotheses related to the impact of changing early circumstances on differences of growth outcomes for parents and offspring
4.8: Stature increase between generations as a result of lower limbs
Chapter 5: Discussion
5.1: Social histories and family backgrounds
5.2: Evaluating relationship between developmental circumstances of parents and offspring and anthropometric measures
5.3: Evaluating relationship between developmental circumstances of parents and offspring and linear enamel hypoplasia
5.4: Future research directions
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How do variation in familial circumstances and the timing of stressors influence body proportions within Punjabi migrant families?