Even minimal cigarette use significantly increases heart disease and mortality risk

Smoking even 2-5 cigarettes a day can more than double your risk of any type of heart disease and raise your risk of death from any cause by 60% compared to people who never smoked, according to new research supported by the American Heart Association's Tobacco Center for Regulatory Science and published in PLOS Medicine. The study found that even after you stop smoking, it could take up to 30 years or more to achieve the same level of health of someone who never smoked.

According to the U.S. Centers for Disease Control and Prevention, while cigarette smoking in the U.S. is on the decline, tobacco product use, which includes cigarettes, remains the leading cause of preventable disease and death. Cigarettes continue to be the most commonly used tobacco product in adults.

In recent years, there has been an increase in the number of people who still smoke, but smoke less. As smoking patterns shift with more people smoking fewer cigarettes, it's important to understand the cardiovascular risks of low-intensity smoking and the long-term benefits of quitting. We could not clearly answer these questions in the past, but the scope of this study, reflecting more than 320,000 U.S. adults over 20 years, gives us the statistical power to see relationships that other smaller studies cannot."

Michael J. Blaha, M.D., M.P.H., study author, lead investigator for the American Heart Association's Tobacco Center for Regulatory Science grant-funded research initiatives

The Cross Cohort Collaboration-Tobacco research group harmonized information (meaning they integrated and standardized studies to make them comparable) from 22 long-term studies of predominately U.S. adults who smoked and those who did not. Researchers used the collective data in their analysis of more than 320,000 adults followed over 20 years. They looked at the relationships among smoking burden, intensity and cessation duration across cardiovascular results, including heart attack, stroke, heart disease, cardiovascular disease (including heart disease and stroke), heart failure and atrial fibrillation (AFib), as well as deaths from coronary heart disease, cardiovascular disease and all causes.

Defining cigarette use as a lifetime use of at least 100 cigarettes, the researchers documented more than 125,000 deaths and 54,000 cardiovascular events.

They found:

• Compared with never-smoking, smoking 2-5 cigarettes daily was associated with a 50% higher risk any type of cardiovascular disease, and 60% increased risk of death from any cause.
• Smoking 11 to 15 cigarettes a day conferred an 84% higher risk of cardiovascular disease and more than twice the risk of death from all causes.
• Quitting smoking immediately decreases health risks and continues to substantially decrease those risks in the first 20 years. However, it may take up to 31 to 40 years of smoking abstinence for people who formerly smoked to have risk levels that approach those of those individuals who never smoked. (Previous studies showed a range of 2 to 29 years that people who formerly smoked are required for their risk to return to the same level as those who have never smoked.)

"Collectively, the findings suggest that no level of smoking is without risk. Smoking one or fewer cigarettes a day was linked to elevated risks for all heart diseases and reasons for death studied, except for stroke and AFib. Smoking a little more - two to five cigarettes daily - was associated with increases for all risks in the study," said Blaha, a professor of cardiology and epidemiology and director of clinical research at the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, Baltimore, Maryland. "Even we were surprised by the strength of harm from even a low quantity of cigarettes, and the incredible importance that and quitting early had on long-term heart health."

"The message here is clear - don't smoke - and for those who do, quit early in life and strive to quit entirely versus smoking less, because even occasional use of tobacco has substantial health consequences," said Stacey E. Rosen, M.D., FAHA, volunteer president of the American Heart Association and senior vice president of women's health and executive director of the Katz Institute for Women's Health of Northwell Health in New York City. "This study provides clear evidence of the harmful impact of smoking on individuals. It offers a framework for future research to delve into the complex dynamics among smoking habits, various population subgroups and their associations with cardiovascular health outcomes."

Among the study's limitations, it did not include specific other causes of death, such as cancer, for a comparison. And while researchers considered the baseline smoking status for participants' smoking behaviors, they did not analyze potential smoking behavior changes over time. Information was also lacking about participants' use of other tobacco products.

Research from the American Heart Association's Tobacco Center of Regulatory Science is jointly funded by the U.S. Food and Drug Administration and the National Institutes of Health. Through the Center, the Association works closely with investigators at institutions across the country to pursue research that adds to the existing knowledge about the health impacts of smoking and nicotine-related products including e-cigarettes, findings that can help inform public health and the regulation of tobacco products.