Twin children in The Gambia: evidence for genetic regulation of physical characteristics in the presence of sub-optimal nutrition

Actual exclusive breastfeeding rates and determinants among a cohort of children living in Gampaha district Sri Lanka: A prospective observational study

BACKGROUND

Exclusive breastfeeding (EBF) during the early months of life reduce infant morbidity and mortality. Current recommendation in Sri Lanka is to continue exclusive breastfeeding up to six months of age. Exclusive breastfeeding rates are generally assessed by the 24 recall method which overestimates the actual rates. The objective of this study was to determine actual exclusive breast feeding rates in a cohort of Sri Lankan children and to determine the reasons that lead to cessation of breastfeeding before six months of age.

METHODS

From a cohort of 2215 babies born in Gampaha district, 500 were randomly selected and invited for the study. They were followed up at two (n = 404), four (n = 395) and six (n = 286) months. An interviewer administered questionnaire asked about feeding history and socio-demographic characteristics. Child health development record was used to assess the growth.

RESULTS

Exclusive breastfeeding rates at two, four and six months were 98.0%, 75.4% and 71.3% respectively. The main reasons to stop exclusive breastfeeding between two to four months was concerns regarding weight gain and between four to six months were mothers starting to work. Majority of the babies that were not exclusively breastfed still continued to have breast milk. Mothers above 30 years had lower exclusive breastfeeding rates compared to younger mothers. Second born babies had higher rates than first borns. There was no significant association between maternal education and exclusive breastfeeding rates.

CONCLUSIONS

Exclusive breastfeeding rates were high among this cohort of children. A decrease in EBF was noted between two and four months. EBF up to six months does not cause growth failure. Mothers starting to work and concerns regarding adequacy of breast milk were the major reasons to cease EBF. The actual exclusive breastfeeding rates up to six months was 65.9%.

Final adult height of children with inflammatory bowel disease is predicted by parental height and patient minimum height Z-score

BACKGROUND

This study was designed to elucidate the contribution of parental height to the stature of children with inflammatory bowel disease (IBD), who often exhibit growth impairment. Accordingly, we compared patients' final adult heights and target heights based on measured parental heights and examined predictors of final adult height in pediatric IBD patients.

METHODS

We prospectively analyzed the growth of 295 patients diagnosed between ages 1 and 18 (211 Crohn's disease [CD], 84 ulcerative colitis [UC]) and their family members (283 mothers, 231 fathers, 55 siblings).

RESULTS

Twenty-two percent had growth impairment (height for age Z-score <-1.64, equivalent to <5th percentile on growth curve) in more than 1 measurement since diagnosis; most growth-impaired patients had CD (88% CD versus 12% UC). Parents of the growth-impaired group had lower mean height Z-scores compared to parents of nongrowth-impaired patients (-0.67 versus 0.02 for mothers [P < 0.001]; -0.31 versus 0.22 for fathers [P = 0.002]). For 108 patients who reached adult heights and had available parental heights, the growth-impaired group continued to demonstrate lower adult height Z-scores (-1.38 versus 0.07; P < 0.001). Adult heights were within 1 SD of target heights even for the growth-impaired group. Only 11.3% remained persistently growth-impaired in adulthood. Multivariate regression analysis demonstrated lower parental height and minimum patient height Z-score as significant predictors of lower final adult height in IBD.

CONCLUSIONS

Parental height is a powerful determinant of linear growth even in the presence of chronic inflammation, and should be an integral part of the evaluation of growth in IBD children.

Longitudinal estimates of puberty timing in Senegalese adolescent girls

This study aimed to assess the timing of sexual maturation (breast development and menarche occurrence) among sub-Saharan African adolescent girls from rural areas. In the framework of a longitudinal study of growth at puberty, the stages of pubertal development (Tanner classification) and menarche occurrence were recorded at intervals between 1995 and 2000 in a sample of 406 Senegalese adolescent girls from a rural area. Nutritional status was estimated during infancy, childhood, and adolescence within this sample, and body composition was estimated only during adolescence. At the beginning of the study (1995), the adolescent girls were 11.4 years old (SD = 0.6). At the end of the study, they were 16.5 years old (SD = 0.6). Median and quartile ages at entry into each maturity stage and its confidence limits were estimated by a lognormal parametric survival model. These adolescent girls were shorter and thinner than girls of the same age from developed countries. Median age at the onset of breast development was 12.6 years (95% CI = 12.5-12.8). Median age at the end of sexual maturation and median age at menarche were estimated respectively at 15.8 years (95% CI = 15.7-15.9) and 15.9 years (95% CI = 15.7-15.9). These adolescent girls were less mature than other adolescent girls of the same age from other developing countries. Their puberty was extremely delayed compared to that of adolescent girls of the same age from industrialized countries. Puberty in these Senegalese adolescent girls is delayed by about 3 years. This may be due to malnutrition, significant energy expenditure, and poor diet and living conditions, and possibly to genetic control.

Genetic approaches to stature, pubertal timing, and other complex traits

The factors that regulate the timing of puberty remain largely elusive, as do the factors that modulate childhood growth and adult height. However, it is clear that these developmental processes are highly heritable--much of the natural variation in growth and timing of puberty is due to genetic variation within the population. In this review, we discuss how recent genetic and genomic advances can be exploited to help understand the genetic regulation of these processes. In particular, we describe how genome-wide linkage scans and association studies, in conjunction with haplotype-based approaches, are potentially useful tools to increase our understanding of these two complex traits. Discovery of the genetic variants that regulate these two traits would expand our understanding of human neuroendocrinology, postnatal development, and the general architecture of complex genetic traits.

Genomewide linkage analysis of stature in multiple populations reveals several regions with evidence of linkage to adult height

Genomewide linkage analysis has been extremely successful at identification of the genetic variation underlying single-gene disorders. However, linkage analysis has been less successful for common human diseases and other complex traits in which multiple genetic and environmental factors interact to influence disease risk. We hypothesized that a highly heritable complex trait, in which the contribution of environmental factors was relatively limited, might be more amenable to linkage analysis. We therefore chose to study stature (adult height), for which heritability is approximately 75%-90% (Phillips and Matheny 1990; Carmichael and McGue 1995; Preece 1996; Silventoinen et al. 2000). We reanalyzed genomewide scans from four populations for which genotype and height data were available, using a variance-components method implemented in GENEHUNTER 2.0 (Pratt et al. 2000). The populations consisted of 408 individuals in 58 families from the Botnia region of Finland, 753 individuals in 183 families from other parts of Finland, 746 individuals in 179 families from Southern Sweden, and 420 individuals in 63 families from the Saguenay-Lac-St.-Jean region of Quebec. Four regions showed evidence of linkage to stature: 6q24-25, multipoint LOD score 3.85 at marker D6S1007 in Botnia (genomewide P<.06), 7q31.3-36 (LOD 3.40 at marker D7S2195 in Sweden, P<.02), 12p11.2-q14 (LOD 3.35 at markers D12S10990-D12S398 in Finland, P<.05) and 13q32-33 (LOD 3.56 at markers D13S779-D13S797 in Finland, P<.05). In a companion article (Perola et al. 2001 [in this issue]), strong supporting evidence is obtained for linkage to the region on chromosome 7. These studies suggest that highly heritable complex traits such as stature may be genetically tractable and provide insight into the genetic architecture of complex traits.

Causes of mortality in twins in a rural region of The Gambia, West Africa

Little is known about birth or mortality rates of twins in The Gambia. There are no reports of the causes of death among twins in sub-Saharan Africa. We identified twin births and deaths from a community-based study which had been carried out in a large rural region of The Gambia over a 5-year period from 1989 to 1993. The overall twinning rate excluding stillbirths was 14.3 (95% CI 12.9, 15.8) per 1000 live deliveries. This was significantly lower among the Mandinka ethnic group (8.8 per 1000) than among the Serahulis (15.1 per 1000) or Fulas (18.3 per 1000). The early-neonatal, late-neonatal and post-neonatal twin mortality rates were 114.0, 45.9 and 64.2 per 1000 live twin births, respectively. In comparison, the early-neonatal, late-neonatal and post-neonatal mortality rates of singletons were 18.6, 16.0 and 41.1 per 1000, respectively. In the post-neonatal period, malnutrition was more frequently a cause of death among twins than among singletons (7.8 per 1000 twin births vs 2.0 per 1000 singleton births; p = 0.0008). Appropriate strategies for preventing malnutrition are required for this high-risk group.