Association between birth weight and adult blood pressure in twins: historical cohort study.
OBJECTIVE
To evaluate the associations in twins between within pair differences in birth weight and subsequent blood pressures as adults thereby removing the impact of potential parental confounding variables.


METHODS
Historical cohort study.


METHODS
St Thomas's UK adult twin register, June 1992 to September 1995.


METHODS
492 pairs of female twins (mean age 54 years).


METHODS
Mean within pair differences in adult blood pressure in each of four strata of within pair differences in birth weight (0, 1-500 g, 501-1000 g, >1000 g). Differences in blood pressure were analysed before and after adjustment for potential confounders between adult twins, after exclusion of those twin pairs including at least one twin taking antihypertensive drugs, and by zygosity.


RESULTS
Reported mean birth weights of heavier and lighter twins were 2.51 (SD 0.61) v 2.12 (0.59) kg respectively. A graded inverse relation between strata of within pair differences in birth weight and differences in adult blood pressure was apparent, with an adjusted blood pressure range of 8.7/5.1 mm Hg across the four strata (test for trend: systolic, P=0.05; diastolic, P=0.09). After excluding those women taking antihypertensive drugs the significance of the association was similar (systolic, P=0.04; diastolic, P=0.10). When differences in blood pressure were stratified for zygosity similar but non-significant trends were apparent.


CONCLUSIONS
It would seem that birth weight is inversely associated with adult blood pressure and that this association is independent of parental confounding variables probably including, in view of the findings in monozygotic twins, genetic factors. The observed blood pressure differences are likely to result from retarded intrauterine growth due to placental dysfunction rather than inadequate maternal nutrition.
Poulter
N R
NR
Cardiovascular Studies Unit, Department of Clinical Pharmacology, Imperial College School of Medicine, St Mary's Campus, London W2 1PG. n.pulter@ic.ac.uk
Chang
C L
CL
MacGregor
A J
AJ
Snieder
H
H
Spector
T D
TD
D000328:Adult; D000428:Alcohol Drinking / Q000453:epidemiology; D001724:Birth Weight / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008131:London / Q000453:epidemiology; D008297:Male; D012907:Smoking / Q000453:epidemiology; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic