E-cigarettes containing nicotine could increase the risk of heart attacks and strokes, according to new research.
The study by scientists in Sweden has linked vaping devices containing nicotine to increases in blood pressure, heart rate and stiffening in arteries after 30 minutes of use.
However, e-cigarettes without nicotine had no similar effects on those who took part in the experiment.
None of the 15 healthy volunteers who participated in the study had used e-cigarettes before.
Dr Magnus Lundback, from the Karolinska Institute, said: “The number of e-cigarette users has increased dramatically in the last few years. E-cigarettes are regarded by the general public as almost harmless.”
The long-term adverse effects of nicotine itself have been difficult for researchers to establish, as it is usually consumed through tobacco products which contain many other chemicals.
“The industry markets their product as a way to reduce harm and to help people to stop smoking tobacco cigarettes.
“However, the safety of e-cigarettes is debated, and a growing body of evidence is suggesting several adverse health effects.”
Although the adverse effects uncovered by the experiments were temporary, Dr Lundback said that chronic exposure to e-cigarettes with nicotine could have permanent effects.
He added: “The results are preliminary, but in this study we found there was a significant increase in heart rate and blood pressure in the volunteers who were exposed to e-cigarettes containing nicotine.
“Arterial stiffness increased around threefold in those who were exposed to nicotine-containing e-cigarettes compared with the nicotine-free group.”
The Royal College of Physicians issued a report last year stating that public health policy should encourage tobacco users to switch to a substitute nicotine product.
It said that “the hazard to health arising from long-term vapour inhalation from the e-cigarettes available today is unlikely to exceed 5% of the harm from smoking tobacco”.