Smoking’s ill effects on human health are well known. But electronic cigarettes have only been around for about 15 years. So there hasn’t yet been time to demonstrate any long-term risks. Still, short-term data already point to vaping’s risks to the lungs and DNA. Now a mouse study shows that even brief exposure to e-cigarette vapors hurts blood vessels.
Effects seen in mice after eight months of vaping were striking. Even more concerning: Just five minutes of vaping damaged their blood vessels. These types of injury increase the risk of developing heart disease. The findings therefore add to a growing list of harm being linked to vaping.
I. Mark Olfert works at West Virginia University in Morgantown. As a physiologist, he studies how the body works. His research focuses on the lungs, heart and blood circulation. Doctors in his state have been considering recommending vaping as a way to help their patients quit smoking. This concerned Olfert. When it came to the heart, he notes, "There really wasn't any information whether e-cigarettes were safe."
So his team decided to test the effects of long-term vaping in mice. They placed the animals in a chamber filled with e-cigarette vapor for four hours daily. They continued this for eight months. The exposures these mice got was no higher than what an average vaper now experiences, Olfert reports. Mice live for two to three years. So their eight months of vaping was about the same as 20 years of vaping by a human.
Arteries carry blood from the heart to the blood vessels that feed cells in even the most distant tissues of the body. The researchers measured the stiffness of a primary artery running from the heart into the lower chest. Mice exposed to the vapors had arteries that were 2.5 times stiffer than normal. Stiff blood vessels can lead to life threatening heart disease.
However, in these tests, just five minutes of vaping also had a clear impact. When muscles in an artery’s walls are stimulated, they contract. This temporarily reduces the size of the tube’s interior. That also ups an individual’s blood pressure. So it’s important that blood vessels don’t stay contracted for too long. But after a mouse had vaped, its artery responded more slowly than normal to chemicals that instruct it to relax, or dilate. The artery's slow response could weaken the heart over time, Olfert says.
Taken together, he concludes, these data suggest that even brief vaping is not safe for the heart. His team described its findings online November 2 in the Journal of Applied Physiology.
Mice are different from people, Olfert points out. But often, not that much different. For instance, cigarette smoking has similar effects in mice and people. That's one reason his team expects its rodent data may predict human heart impacts from vaping. And while it would be nice to have actual human data for comparison, it could take 20 or 30 more years before long-term vaping data would be available from people, he notes.
Importance for teens
Vaping research is especially important for young people, who might unknowingly put their health at risk. "With adolescents, we are really concerned," stresses Olfert, “because right now the message they get is that these things are safe.” In fact, he notes, a wealth of emerging data suggest e-cigarettes aren’t.
Holly Middlekauff agrees. She is a heart doctor at the University of California in Los Angeles who did not take part in the new study. Many people today view vaping as harmless. And that, she says, is a mistake. Such a belief, she worries, may lead teens who would otherwise not have tried traditional tobacco cigarettes to experiment with vaping.
The next step is to find out which part of an e-cigarette's vapor is responsible for the artery and blood-vessel impacts. "Is it the nicotine,” asks Olfert? “Is it the base chemicals that are in the [vaporized] liquid? Or is it the flavoring?” Right now, he notes, “we don't know.”
Middlekauff suspects nicotine might be the heart-toxic component. Nicotine is a natural chemical in tobacco that makes cigarettes addictive. The toxicity of smoking is usually blamed mostly on the tars that form when tobacco is burned. As e-cigarettes “burn” nothing, some people had assumed vaping was harmless. But the safety of inhaled nicotine is not proven, Middlekauff points out. In fact, there are reasons to believe that nicotine may be particularly harmful to teens.
Her team recently tested the effects of e-cigarettes with and without nicotine in human volunteers. People who inhaled vapors containing nicotine showed fluctuating heart rates. That is what people would expect from nicotine. So the new data seem to affirm that nicotine “may underlie the adverse effects on the heart," she says. Her team reported its findings in the September Journal of the American Heart Association.
Olfert’s group is continuing to study long-term effects of vaping on blood vessels. These researchers have even begun a study in people based on their results in mice.
For now, Middlekauff urges, teens should know that vaping is not harmless. "If you are a non-smoker,” she says, you definitely “should not start using electronic cigarettes."
addictive An adjective to describe something that become habit-forming in an uncontrolled or unhealthy way. This can include a drug or some habit (such as video game playing or phone texting). Such addictions reflect an illness triggered by brain changes that occur after using some drugs or engaging in some extremely pleasurable activities. People with an addiction will feel a compelling need to use a drug (which can be alcohol, the nicotine in tobacco, a prescription drug or an illegal chemical such as cocaine or heroin), even when the user knows that doing so risks severe health or legal consequences.
adolescent Someone in that transitional stage of physical and psychological development that begins at the onset of puberty, typically between the ages of 11 and 13, and ends with adulthood.
animal model A nonhuman animal used to stand in for people in research testing. Which animal a lab uses will depend on how closely parts of its body or chemical-signaling systems match those in people.
artery Part of the body’s circulation system. There are several. Each is a major tube running between the heart and blood vessels that will move blood to all parts of the body.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
blood vessel A tubular structure that carries blood through the tissues and organs.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
component Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).
e-cigarette (short for electronic cigarette) Battery-powered device that disperses nicotine and other chemicals as tiny airborne particles that users can inhale. They were originally developed as a safer alternative to cigarettes that users could use as they tried to slowly break their addiction to the nicotine in tobacco products. These devices heat up a flavored liquid until it evaporates, producing vapors. People use these devices are known as vapers.
heart rate Heart beat; the number of times per minute that the heart — a pump — contracts, moving blood throughout the body.
information (as opposed to data) Facts provided or trends learned about something or someone, often as a result of studying data.
journal (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.
model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.
nicotine A colorless, oily chemical produced in tobacco and certain other plants. It creates the “buzz” associated with smoking. Highly addictive, nicotine is the substance that makes it hard for smokers to give up their use of cigarettes. The chemical is also a poison, sometimes used as a pesticide to kill insects and even some invasive snakes or frogs.
physiologist A scientist who studies the branch of biology that deals with how the bodies of healthy organisms function under normal circumstances.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
rodent A mammal of the order Rodentia, a group that includes mice, rats, squirrels, guinea pigs, hamsters and porcupines.
tar A thick, viscous black flammable goo, often derived from plants (such as wood) or plant-based materials (such as coal). Tar consists of a range of hydrocarbons, resins, alcohols and more.
tissue Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
tobacco A plant cultivated for its leaves, which many people burn in cigars, cigarettes, and pipes. Tobacco leaves also are sometimes chewed. The main active drug in tobacco leaves is nicotine, a powerful stimulant (and poison).
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
vaping (v. to vape) A slang term for the use of e-cigarettes because these devices emit vapor, not smoke. People who do this are referred to as vapers.
vaporize To convert from a liquid to a gas (or vapor) through the application of heat.
vapors Fumes released when a liquid transforms to a gas, usually as a result of heating.
Journal: I.M. Olfert et al. Chronic exposure to electronic cigarette (E-cig) results in impaired cardiovascular function in mice. Journal of Applied Physiology. Published online November 2. doi: 10.1152/japplphysiol.00713.2017.
Journal: R.S. Moheimani et al. Sympathomimetic effects of acute e-cigarette use: Role of nicotine and non-nicotine constituents. Journal of the American Heart Association. Vol. 6, September 2017. doi: 10.1161/JAHA.117.006579.
Meeting: I.M. Olfert et al. Acute and chronic effects of e-cigarette vapor exposure on vascular function: new friend or old foe? American Physiological Society Conference: Cardiovascular Aging: New Frontiers and Old Friends. August 11-14, 2017. Westminster, Colo. Abstract 5.3.