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Assessing newborn body composition using principal components analysis: differences in the determinants of fat and
Beverley M Shields1, Bridget A Knight, Roy J Powell
1Peninsula Medical School, Barrack Road, Exeter, UK. B.Shields@exeter.ac.uk
Insights
Birth weight comprises skeletal size and fat, which have different growth patterns and determinants. Understanding these distinct components is crucial for studying birth weight
Area of Science:
- Human Growth and Development
- Pediatric Endocrinology
- Biostatistics
Background:
- Birth weight is a complex measure influenced by both skeletal size and soft tissue (fat).
- These two components of birth weight may follow distinct growth trajectories and be influenced by different factors.
Purpose of the Study:
- To investigate the associations between established determinants of birth weight and its separate components: skeletal size and fat.
- To determine if factors influencing skeletal size differ from those influencing fat mass at birth.
Main Methods:
- Utilized anthropometric measurements (weight, length, circumferences, skinfolds) from 699 healthy, term UK infants and their parents.
- Applied principal components analysis with varimax rotation to derive independent measures of skeletal size and fat for infants and parents.
- Analyzed correlations between anthropometric components and factors like gestational age, parental characteristics, maternal smoking, parity, and maternal glucose levels.
Main Results:
- Gestational age was significantly associated with skeletal size, but not fat mass.
- Skeletal size at birth showed significant correlations with parental skeletal size and was negatively impacted by maternal smoking.
- Fat mass at birth was associated with parity, maternal glucose levels, and maternal fat mass.
Conclusions:
- Principal components analysis effectively distinguishes skeletal size and fat as meaningful components of birth weight.
- These components exhibit differential associations with known determinants, suggesting distinct regulatory mechanisms for skeletal and fat growth.
- Recognizing these differences is vital for understanding the link between birth weight components and later adult disease risk.
Background:
Birth weight is a composite of skeletal size and soft tissue. These components are likely to have different growth patterns. The aim of this paper is to investigate the association between established determinants of birth weight and these separate components.
Methods:
Weight, length, crown-rump, knee-heel, head circumference, arm circumference, and skinfold thicknesses were measured at birth in 699 healthy, term, UK babies recruited as part of the Exeter Family Study of Childhood Health. Corresponding measurements were taken on both parents. Principal components analysis with varimax rotation was used to reduce these measurements to two independent components each for mother, father and baby: one highly correlated with measures of fat, the other with skeletal size.
Results:
Gestational age was significantly related to skeletal size, in both boys and girls (r = 0.41 and 0.52), but not fat. Skeletal size at birth was also associated with parental skeletal size (maternal: r = 0.24 (boys), r = 0.39 (girls) ; paternal: r = 0.16 (boys), r = 0.25 (girls)), and maternal smoking (0.4 SD reduction in boys, 0.6 SD reduction in girls). Fat was associated with parity (first borns smaller by 0.45 SD in boys; 0.31 SD in girls), maternal glucose (r = 0.18 (boys); r = 0.27 (girls)) and maternal fat (r = 0.16 (boys); r = 0.36 (girls)).
Conclusion:
Principal components analysis with varimax rotation provides a useful method for reducing birth weight to two more meaningful components: skeletal size and fat. These components have different associations with known determinants of birth weight, suggesting fat and skeletal size may have different regulatory mechanisms, which would be important to consider when studying the associations of birth weight with later adult disease.
