Do genetic factors contribute to the association between birth weight and blood pressure?
- aInstitute of Public Health, Epidemiology, and Institute for Demography and Statistics, University of Southern Denmark, Odense, Denmark, bDepartment of Psychology, University of Minnesota, Minneapolis, USA
- Dr Christensen, Institute of Public Health (Epidemiology), University of Southern Denmark, Sdr Boulevard 23A, DK-5000 Odense C, Denmark (KChristensen{at}health.sdu.dk)
- Accepted 12 March 2001
Abstract
OBJECTIVES To evaluate whether genetic factors contribute to the association between low birth weight and increased blood pressure among adolescents.
DESIGN Historical cohort study of twin pairs. It was evaluated whether (1) a negative association between birth weight and systolic blood pressure was found in the overall twin sample and (2) whether the intrapair difference in birth weight correlated with the intrapair difference in systolic blood pressure—thereby controlling for the effect of genetic factors (all in monozygotic and on average half in dizygotic pairs).
SETTING The Minnesota Twin Family Study.
PARTICIPANTS 1311 pairs of adolescent twins.
MAIN RESULTS A negative association between birth weight and systolic blood pressure was retrieved in the overall sample. The regression coefficient after controlling for current weight was −1.88 mm Hg/kg (SE 0.61), which corresponds to results from previous studies of singleton adolescents. The regression coefficient fell to −0.64 mm Hg/kg (SE 0.86) when the intrapair analyses were used. The largest reduction was observed among monozygotic twins: from −2.44 mm Hg/kg (SE 0.75) in the overall monozygotic twin sample to −1.06 mm Hg/kg (SE 1.14) in the analyses of the within monozygotic pair differences.
CONCLUSION The association between low birth weight and increased blood pressure later in life is well established. “The fetal programming hypothesis” suggests that the association is caused by intrauterine malnutrition while a new hypothesis “the fetal insulin hypothesis” proposes that genetically determined insulin resistance also contributes significantly to the association. A recent twin study of middle aged twins showed no evidence for an influence of genetic factors while this larger study provides support for the fetal insulin hypothesis: the association between birth weight and blood pressure attenuated among adolescents when genetic factors were controlled. Together this suggests an important contribution of genetic factors to the association between fetal growth and systolic blood pressure in adolescence.
Footnotes
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Funding: the activities of the Danish Center for Demographic Research are funded by a grant from the Danish National Research Foundation. The Minnesota Twin Family Study is supported by United States Public Health Service Grants DAO1957 and AA. K Christensen is supported by the US National Institutes of Health (grant AG08761).
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Conflicts of interest: none.
