Although companies market e-cigarettes as a safer alternative to smoking tobacco, in recent years research has shown that these popular smoking devices pose dangerous health risks. Now, new findings presented at the European Respiratory Society International Congress suggest that e-cigs that contain nicotine—a highly addictive drug—are linked to increased arterial stiffness, heart rate and blood pressure, reports EurekAlert!

For the study, researchers recruited 15 healthy participants to determine the safety and health effects of e-cigarettes. The volunteers rarely smoked cigarettes (defined as smoking a maximum of 10 per month); their average age was 26; and 59 percent were female, and 41 percent were male.

Scientists randomized participants to use e-cigarettes with nicotine for 30 minutes on one day and e-cigarettes without the stimulant on another day. Researchers then measured their blood pressure, heart rate and arterial stiffness immediately after they smoked the e-cigs, as well as two and four hours later.

Findings showed that during the first 30 minutes, those who smoked e-cigarettes with nicotine suffered a substantial rise in blood pressure, heart rate and arterial stiffness, all of which are associated with an increased risk of heart attacks and strokes. (Arterial stiffness increased almost three times in these users.) What’s more, volunteers who smoked e-cigs without nicotine were untroubled by these effects.

“It is very important that the results of this and other studies reach the general public and the health care professionals working in preventive health care, for example in smoking cessation,” said Magnus Lundbäck, MD, PhD, a leader of the research team and clinical registrar at the Danderyd University Hospital, Karolinska Institute in Sweden. “Our results underline the necessity of maintaining a critical and cautious attitude toward e-cigarettes, especially for health care professionals. E-cigarette users should be aware of the potential dangers of this product so that they can decide whether to continue or quit based on scientific facts.”

The scientists plan to further evaluate the effects e-cigarettes may have on blood vessel and lung functions. In addition, the researchers intend to conduct lab studies to learn how e-cigarette vapor and liquid affect cell cultures.

Click here to read about the unsafe effects of liquid nicotine in e-cigarettes on children.