Background: The negative effect of birthweight on systolic blood pressure has been suggested to be initiated in utero and amplified with age. We aimed to investigate this hypothesis.
Methods: A sample of 3634 people from a birth cohort study of men and women born in Britain in 1946 were included in analyses. Cohort members have been contacted regularly since birth, and systolic and diastolic blood pressures were measured at ages 36, 43, and 53 years. Multilevel models, with blood pressure as a repeated outcome, were used to test the amplification hypothesis and to compare results for birthweight with those for childhood social class.
Findings: Considering both men and women together, a consistent negative association between birthweight and systolic blood pressure was noted from age 36 to 53 years, but no evidence was recorded of substantial amplification with age. A 1 kg higher birthweight was associated with a slower mean increase in systolic blood pressure by -0.4 mm Hg (95% CI -1.3 to 0.4; p=0.3) per 10-year increase in age. Birthweight was not associated with diastolic blood pressure at any age. People from a manual social class in childhood had higher systolic and diastolic blood pressure than did those from a non-manual class. The effect on systolic blood pressure rose with age, by 1.0 mm Hg (95% CI 0.1 to 2.0; p=0.03) per 10 years, but was largely accounted for by current body-mass index, which was an increasingly strong determinant of blood pressure.
Interpretation: These findings suggest that weight control throughout life is key to prevention of raised blood pressure during middle age. Understanding the link between the early childhood socioeconomic environment and adult obesity could make this strategy more effective.