Within an hour, arteries that feed blood to and from the heart narrow by around 30 per cent, and their ability to widen—a process known as vasodilation—is also affected, say researchers from West Virginia University.
The damage can be done by smoking just one e-cigarette and for only five minutes. They shouldn't be seen as safe, or even as a safer option to real cigarettes, say the researchers.
They tested the cigarettes' effects on the diameter of blood vessels, and any aortic (the heart's main artery) stiffness on a group of laboratory mice. Aortic stiffness is an indicator of heart disease and is usually seen in older people.
The effects were seen within the first hour, and symptoms worsened with more persistent use of e-cigarettes. Aortic stiffness was twice as bad as in non-smokers when the mice were exposed to 20 hours of e-cigarette vapour for eight months.