This project studied the age-related alterations that occur in the cardiovascular system – the heart, lungs and network of arteries and veins that carry oxygenated blood and nutrients to every cell of the body and remove the waste products of metabolism. It was already known that the phase of breathing affects the rate at which the heart beats, but that this effect decreases as we age. The research has associated this reduction in heart-lung interaction with changes in the endothelium, the inner lining of all the blood vessels. It involved making non-invasive measurements of blood flow in the skin of 200 healthy subjects of all ages. The analysis focused on very low frequency oscillations in blood flow that can give a measure of the state of the endothelium.