Smoking can cause heart attacks and strokes. Many smokers don’t know that

By Katia Hetter, CNN

(CNN) — Smoking cigarettes doesn’t just cause lung cancer. The toxic smoke affects nearly every organ in the body — yet some of its most serious consequences may be less widely recognized.

Smoking is a major cause of cardiovascular disease, including heart attacks and strokes, and exposure to secondhand smoke puts people who don’t smoke at risk, too.

A recent study published in the journal BMJ Open found major gaps in how well people who smoke understand these risks. While more than 9 in 10 people surveyed across 46 countries knew that smoking causes lung cancer, substantially fewer knew of its cardiovascular effects. Awareness of the cardiovascular dangers of secondhand smoke was even lower.

Why does smoking have such profound effects on the heart and blood vessels? How dangerous is secondhand smoke, and what should people who smoke and those around them know?

To guide us through this research and the questions it raises, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously served as Baltimore’s health commissioner.

CNN: How well do people understand the health risks of smoking?

Dr. Leana Wen: The researchers in this study analyzed data from two major international tobacco surveys. One was the International Tobacco Control Project, which included surveys from 26 countries conducted between 2002 and 2022. The other was the Global Adult Tobacco Survey, which used surveys from 32 countries conducted between 2008 and 2020. Some countries participated in both; overall, 46 countries were represented.

Participants, who were smokers age 18 and older, were asked whether they knew or believed that smoking causes lung cancer, heart disease or heart attack, and stroke. They were also asked whether secondhand smoke causes lung cancer and heart disease or heart attack in people who do not smoke.

The researchers analyzed the two survey datasets separately, and the results were consistent. About 92% of people who smoked knew that smoking can cause lung cancer. By comparison, 85% of survey participants in one analysis knew about the connection with heart disease, and 80% in the other knew about the link with heart attack. Just 75% and 66%, respectively, knew that smoking is associated with stroke.

The gaps were even greater for secondhand smoke. Depending on the survey, 77% to 82% knew that secondhand smoke causes lung cancer, while only 62% to 73% knew it causes heart disease or heart attack.

Another eye-catching finding was how little overall progress there had been over time. Across the five health effects studied, the average increase in knowledge was just 0.14 percentage point per year.

CNN: So many people who smoke don’t know about the cardiovascular risks. Is that concerning?

Wen: Smoking is one of the major preventable causes of cardiovascular disease. In fact, the researchers point out that worldwide, heart disease and stroke together accounted for about 2.6 million deaths attributable to smoking in 2019. That was twice the 1.3 million smoking-attributable deaths from cancers of the lung, trachea and bronchus. Someone who thinks the primary danger of cigarettes is lung cancer is missing a major part of the picture.

Knowledge influences behavior. Someone who understands all the risks may be more motivated to quit. This really matters for secondhand smoke, too. If people who smoke do not realize that their smoke increases cardiovascular risk in those around them, they may not be taking precautions to protect family members, friends and coworkers from exposure.

CNN: How does smoking cause heart attacks and strokes?

Wen: Cigarette smoke contains thousands of chemicals, including many that damage the cardiovascular system by injuring the inner lining of blood vessels and promoting inflammation. These toxins also contribute to the buildup of plaque inside arteries.

In addition, smoking also makes blood more likely to clot. A heart attack commonly occurs when a clot blocks blood flow through an artery supplying the heart. An ischemic stroke occurs when blood flow to part of the brain is blocked.

Smoking has other cardiovascular effects, too. Nicotine raises heart rate and blood pressure. Carbon monoxide released by combustion reduces the amount of oxygen that the blood can carry. Over time, smoking can narrow and stiffen blood vessels and accelerate cardiovascular disease.

These effects are not limited to people who have smoked heavily for decades. Cardiovascular damage begins early, and relatively low levels of cigarette smoking can carry substantial risk.

CNN: How dangerous is secondhand smoke to the heart and brain?

Wen: People exposed to secondhand smoke inhale many of the same toxic chemicals as the person smoking. These chemicals can cause similar types of damage to blood vessels, increase inflammation and thus increase the risk of coronary heart disease.

Here, the public health impact is also substantial. The study cites estimates that secondhand smoke caused about 1.3 million deaths worldwide in 2021 among people who did not smoke. Yet, in several high-income countries, including the United States, Canada, England, Australia and Germany, fewer than half knew about this risk.

CNN: Why might people know so much more about the link between smoking and lung cancer than about heart disease and stroke?

Wen: The connection between smoking and lung cancer has been a central part of public health messaging for decades. The link appears prominently in education campaigns and tobacco warnings and, rightfully so, has become ingrained in public consciousness.

The cardiovascular consequences have not achieved the same level of recognition. This study found large differences between countries, which could reflect differences in mass media campaigns and other educational efforts.

CNN: Does cutting down on cigarettes substantially reduce cardiovascular risk, or does someone need to quit completely?

Wen: Cutting down is not the same as quitting. There is a common misconception that someone who smokes only a few cigarettes a day has a small fraction of the cardiovascular risk of someone who smokes a pack a day. That is not the case. Even low levels of cigarette smoking substantially increase cardiovascular risk.

The goal should be to stop smoking completely. The good news is that the cardiovascular benefits begin to accrue quickly after quitting. Heart rate and blood pressure improve, carbon monoxide levels in the blood decline, and over time the risks of heart attack, stroke and other smoking-related diseases all fall substantially.

No smoker should conclude that the damage is already done and that there is no point to stopping now. Quitting is beneficial at any age, and the sooner someone stops, the more health benefit they gain.

CNN: It may seem obvious, but what should people who smoke do for their health and the health of those around them?

Wen: The single most effective step is to quit smoking. There are effective treatments for tobacco dependence, including nicotine replacement therapy and prescription medications. Combining medication with behavioral counseling increases the chance of successfully quitting.

People should speak with their healthcare provider about which treatment is appropriate for them. It is also common to require multiple attempts before quitting for good. An unsuccessful attempt is not a reason to stop trying; it can help someone identify triggers and determine what additional support they need next time.

In the meantime, people who smoke should protect others from secondhand smoke. Smoking in another room or opening a window does not make indoor smoking safe. Never smoke inside the home, car or other enclosed space, and keep smoke away from children, pregnant people, older adults and anyone with cardiovascular or respiratory disease.

Everyone who smokes should know their habit does not just threaten the lungs. Smoking cigarettes damages blood vessels throughout the body and can cause heart attacks and strokes. Understanding the full range of harms provides another powerful reason to quit, for the sake of their health and the health of their loved ones.

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