Quitting smoking can significantly reduce the risk of a heart attack for individuals diagnosed with coronary artery disease, as highlighted by a recent study. However, researchers caution that merely reducing smoking does not substantially lower this risk. Interestingly, individuals who have never smoked continue to have a lower overall risk of major cardiovascular events compared to those who have quit, even if they have been smoke-free for many years.

These findings were presented at the ESC Congress 2024 in London, the annual meeting of the European Society of Cardiology. Though the research has yet to be published in a peer-reviewed journal, experts believe it delivers a vital message.

"This analysis reinforces what has been known from previous smaller studies over the years: there is no safe level of cigarette smoking," said Dr. Richard Wright, a cardiologist at Providence Saint John’s Health Center in Santa Monica, California. He emphasized that the harmful components of cigarette smoke immediately trigger a series of detrimental events, regardless of the quantity smoked, and that even minimal exposure can increase cardiac risk, including for those exposed to secondhand smoke.

The study analyzed data from the CLARIFY registry, which has been instrumental in past cardiovascular research. Researchers examined 32,378 individuals with coronary artery disease, with an average follow-up of about six years post-diagnosis. At the beginning of the study, 41 per cent of participants had never smoked, 46 per cent were former smokers, and 12 per cent were current smokers. Among the former smokers, 73 per cent had quit within a year of their diagnosis, while 27 per cent stopped in subsequent years.

The study revealed that quitting smoking after a coronary artery disease diagnosis reduced the risk of a major cardiovascular event by 44 per cent, regardless of when they quit. However, each additional year of continued smoking increased the risk by 8 per cent. Notably, reducing the amount smoked did not significantly lower the risk compared to those who continued smoking. Former smokers also never reached the lower cardiovascular risk level of those who had never smoked, even after years of cessation.

“I often tell my patients that it is never too soon or too late to stop smoking, though the sooner a patient quits, the better it is to lower cardiovascular risk,” explained Dr Jules Mesnier, a cardiologist at Hospital Bichat-Claude Bernard in Paris and one of the study's authors. He emphasized that reducing smoking is insufficient, and clear messages about the importance of quitting should be a part of every medical consultation.

Dr Robert Page, a professor of clinical pharmacy and a member of the American Heart Association’s Council on Lifestyle and Cardiometabolic Health, underscored the significance of the study’s findings. "Even after quitting, patients do not return to their baseline cardiovascular risk status," he noted. Despite the study being based on registry data, Page highlighted the substantial evidence on the cardiovascular effects of smoking, reinforcing the importance of patient education.

Dr Cheng-Han Chen, an interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in California, echoed the study's findings. "This study confirms that quitting smoking, not just reducing, can cut the risk of major cardiovascular events by half. This aligns with our current understanding and recommendations," he said.

Dr Jayne Morgan, a cardiologist and vice president of medical affairs at Hello Heart, attending the ESC conference, stressed that smoking causes irreversible damage to the coronary arteries' endothelial lining, leading to atherosclerosis, which can result in heart attacks and heart failure. Smoking also accelerates the progression of existing atherosclerosis, narrowing coronary arteries and reducing blood flow to the heart. Furthermore, smoking increases levels of blood clotting factors, heightening the risk of cardiovascular events.

Health experts like Page and Morgan agree that smoking cessation should involve advice, counselling, behavioural interventions, and pharmacological therapy when necessary. Quitting smoking is challenging, but setting a quit date and having support from healthcare professionals can be crucial steps toward success.

For those who don’t smoke, the advice is clear: “Don’t start. If you have started, now is the best time to quit,” said Morgan. Wright added, “If you smoke, quit now. You will see benefits within a month, and in about a decade, the excess risk will disappear — but only if you completely abstain from cigarette smoke.”

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