Retinal vascular network architecture in low-birth-weight men

Background Low birth weight is associated with hypertension and increased cardiovascular mortality, but the mechanism of this association is not known. Hypertension is accompanied by abnormalities of the microvasculature including rarefaction. Objective To test the hypothesis that low birth weight is associated with an alteration in microvascular architecture. Design A stratified random sample of 100 men aged 64-74 years was selected from a cohort of men whose birth weights were known. They were of relatively high or low birth weight (`high' greater than or equal to 3700 g, `low' less than or equal to 3200 g) and high or low systolic blood pressure (high greater than or equal to 160 mmHg, low less than or equal to 140 mmHg). Methods Retinal arteriolar geometry was defined in terms of arteriolar bifurcation angles and junction exponents (a measure of the relative diameters of parent and daughter vessels), measured from photographic diapositives using operator-directed image analysis. Results Members of low-birth-weight groups had significantly narrower bifurcation angles than did members of high-birth-weight groups (74 +/- 1 degrees versus 78 +/- 1 degrees, P = 0.017 by analysis of variance). There was no significant difference between angles in members of groups with high and low blood pressures. Neither birth weight nor blood pressure grouping affected junction exponents. Conclusions Narrower bifurcation angles are associated with increased circulatory energy costs and may be related to a lower than normal microvascular density. Our finding of differences in retinal microvascular architecture might reflect a persistent alteration in vascular architecture as a result of an impairment of foetal development and could provide a mechanistic link between low birth weight and subsequently increased cardiovascular risk.