Electronic cigarettes may increase two separate risk factors for heart disease, a new study finds. The study was small. It looked at just 16 vapers and 18 people who neither smoked nor vaped. Still, the symptoms uncovered were “spot-on” for what has been seen in heart attack patients and those with heart disease and diabetes, says Holly Middlekauff.
She and her coauthors at the University of California, Los Angeles, shared their findings online February 1. They were published in JAMA Cardiology.
Just two or three patients can skew results in a study of this size, notes heart specialist John Ambrose. He works at the University of California, San Francisco and was not involved in the new research. Another issue concerns Ambrose: Some vapers in this study used to smoke cigarettes. That, too, he notes, could skew the data.
Still, he called the new findings interesting. And every new study may be important, he adds. After all, he notes, “the medical community just doesn’t have enough information” yet to fully understand vaping’s impacts on health.
What the study found
Adrenaline — also known as epinephrine — is a natural hormone. It’s best known for its role in the so-called “fight or flight” response. When released into the bloodstream, it increases the rate at which the heart pumps blood around the body. It also ups the breathing rate and can prepare muscles for exertion. People who constantly show high levels of this hormone face a high risk of heart disease. And in the new study, regular vapers had heartbeat patterns that indicated they had high levels of this hormone.
(Nicotine is the addictive substance in both tobacco and the flavored liquids that are vaporized in e-cigarettes. It, too, can boost adrenaline. So the researchers had made their subjects avoid vaping on test days.)
Middlekauff says the new data show that vapers’ hearts are in “flight or fight” mode all the time, not just as they vape.
Her team also found signs of increased cellular stress in regular vapers. The body produces oxidants, reactive molecules that can kill cells. This will get rid of damaged tissues and germs. But too much of these stressful oxidants can damage arteries or narrow them. Environmental conditions can also trigger this. For instance, some air pollutants produce oxidants.
Previous research had linked oxidant stress to e-cigarettes. The new study targeted where it might occur and how it might affect the heart, notes Aruni Bhatnagar. He works for the American Heart Association Tobacco Regulation and Addiction Center. It’s based at the University of Louisville in Kentucky.
This new study “adds to the case that there may be some residual harm associated with e-cigarettes,” he says. (Bhatnagar wrote an editorial on vaping and heart risks in the same issue of JAMA Cardiology.)
Recent studies have linked other health concerns to vaping. Some found high levels of inflammation in the lungs of experimental animals. Others showed e-cig vapors can lower the activity of many human genes linked to immunity and alter genes associated with mental health. And one demonstrated that the intense heating of the solvents in e-liquids by e-cigs creates toxic vapors.
For Middlekauff, the next step will be to nail down exactly what in e-cigarettes triggered the effects that her team turned up. Her group also wants to compare vaping’s heart effects to those caused by smoking.
“Electronic cigarettes aren’t harmless,” Middlekauff concludes. “They have real, measurable physiological effects. And these physiological effects — at least the couple that we found — have been associated with heart disease.”
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adrenaline A hormone produced by glands (adrenal) when someone is stressed by fear, anger or anxiety. It can make the heart beat faster and allow muscles to perform better than normal. Adrenaline is part of the body’s “fight or flight” response to stress. It can briefly help someone run faster or temporarily boost the performance of muscles (as for lifting weights).
cardiology The branch of medicine dealing with functions and diseases of the heart.
cell The smallest structural and functional unit of an organism. Typically too small to see with the naked eye, it consists of watery fluid surrounded by a membrane or wall. Animals are made of anywhere from thousands to trillions of cells, depending on their size. Some organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
coauthor One of a group (two or more people) who together had prepared a written work, such as a book, report or research paper. Not all coauthors may have contributed equally.
diabetes A disease where the body either makes too little of the hormone insulin (known as type 1 disease) or ignores the presence of too much insulin when it is present (known as type 2 diabetes).
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.
e-liquid A term for the solutions heated to the evaporation point in an electronic cigarette. These solutions are the basis of the vapors that will be inhaled. The liquid typically contains a solvent into which flavorings and nicotine have been dissolved.
epinephrine A type of stress hormone, commonly called adrenaline, that is secreted by the adrenal glands. It constricts blood vessels. It also increases the force and rate at which the heart contracts.
gene (adj. genetic) A segment of DNA that codes, or holds instructions, for producing a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
germ Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
heart attack Permanent damage to the heart muscle that occurs when one or more regions of it become starved of oxygen, usually due to a temporary blockage in blood flow.
hormone (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.
immunity The ability of an organism to resist a particular infection or poison by
inflammation The body’s response to cellular injury and obesity; it often involves swelling, redness, heat and pain. It is also an underlying feature responsible for the development and aggravation of many diseases, especially heart disease and diabetes.
nicotine A colorless, oily chemical produced in tobacco and certain other plants. It creates the ‘buzz’ effect associated with smoking. It also is highly addictive, making it hard for smokers to give us 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.
online A term that refers to things that can be found or done on the internet.
physiology (adj. physiological) The branch of biology that deals with the everyday functions of living organisms and how their parts function. Scientists who work in this field are known as physiologists.
reactive (in chemistry) The tendency of a substance to take part in a chemical process, known as a reaction, that leads to new chemicals or changes in existing chemicals.
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. Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.
solvent A material (usually a liquid) used to dissolve some other material into a solution.
stress (in biology) A factor, such as unusual temperatures, moisture or pollution, that affects the health of a species or ecosystem.
subjects (in research) The participants in a trial. The term usually refers to people who volunteered to take part. Some may receive money or other compensation for their participation, particularly if they entered the trial healthy.
symptom A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.
tissue Any of the distinct types of material, comprised of cells, which 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. And brain tissue will be very different from bone or heart tissue.
tobacco A plant cultivated for its leaves. Dried tobacco leaves are burned in cigars, cigarettes, and pipes. Tobacco leaves are also sometimes chewed. The main constituent of tobacco leaves is nicotine.
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.
vapors Fumes released when a liquid transforms to a gas, usually as a result of heating.
JOURNAL: R. Moheimani et al. Increased cardiac sympathetic activity and oxidative stress in habitual electronic cigarette users. JAMA Cardiology. Published online February 1, 2017. doi: 10.1001/jamacardio.2016.5303.
JOURNAL: A. Bhatnagar. Are electronic cigarette users at increased risk for cardiovascular disease? JAMA Cardiology. Published online February 1, 2017. doi: 10.1001/jamacardio.20165550.