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Background: Paternal age at childbirth has been increasing worldwide, and we assessed whether this increase affects growth, body composition and metabolism in their children., Methods: We studied 277 children (aged 3-12 years) born to fathers aged 19·8-51·8 years. Clinical assessments were height and weight adjusted for parental measurements, DEXA-derived body composition, fasting lipids, glucose homoeostasis and hormonal profiles., Results: Children born to fathers aged 31-35 (P = 0·009) and >35 years (P = 0·021) were 2 cm taller than those of fathers aged ≤30 years. Children of fathers aged >35 years at childbirth had a lower body mass index (BMI) (-0·32 SDS) than offspring of fathers aged 31-35 (-0·01 SDS; P = 0·043) and ≤30 (0·22 SDS; P = 0·019). There were marked effects of paternal age at childbirth on childhood blood lipids. LDL-C concentrations in children born to fathers aged >35 years were 11% and 21% higher than in children of fathers aged 31-35 and ≤30 years, respectively (P < 0·01). Total cholesterol to HDL-C ratio was also higher among the children of fathers aged 31-35 (12%; P = 0·014) and >35 (16%; P = 0·004) years at childbirth compared with the ≤30 group. In addition, HOMA-IR in girls (but not boys) born of fathers aged 31-35 (0·99) and >35 years (1·11) indicated better insulin sensitivity compared with offspring in the ≤30 group (1·63; P < 0·05)., Conclusions: Increasing paternal age at childbirth is associated with a more favourable phenotype in their children (taller and slimmer, with better insulin sensitivity in girls) but with a less favourable lipid profile., (© 2013 John Wiley & Sons Ltd.)

Background: There is evidence suggesting that first-born children and adults are anthropometrically different to later-borns. Thus, we aimed to assess whether birth order was associated with changes in growth and metabolism in childhood., Methods: We studied 312 healthy prepubertal children: 157 first-borns and 155 later-borns. Children were aged 3-10 years, born 37-41 weeks gestation, and of birth weight appropriate-for-gestational-age. Clinical assessments included measurement of children's height, weight, fasting lipid and hormonal profiles and DEXA-derived body composition., Results: First-borns were taller than later-borns (P < 0·0001), even when adjusted for parents' heights (0·31 vs 0·03 SDS; P = 0·001). There was an incremental height decrease with increasing birth order, so that first-borns were taller than second-borns (P < 0·001), who were in turn taller than third-borns (P = 0·007). Further, among sibling pairs both height SDS (P = 0·009) and adjusted height SDS (P < 0·0001) were lower in second- vs first-born children. Consistent with differences in stature, first- (P = 0·043) and second-borns (P = 0·003) had higher IGF-I concentrations than third-borns. Both first- (P < 0·001) and second-borns (P = 0·004) also had reduced abdominal adiposity (lower android fat to gynoid fat ratio) when compared with third-borns. Other parameters of adiposity and blood lipids were unaffected by birth order., Conclusions: First-borns were taller than later-born children, with an incremental height reduction from first to third birth order. These differences were present after correction for genetic height, and associated to some extent with alterations in plasma IGF-I. Our findings strengthen the evidence that birth order is associated with phenotypic changes in childhood., (© 2013 John Wiley & Sons Ltd.)