Study: Smoking One Cigarette a Day Harms the Heart at All Levels

SadaNews - Despite decades of research, significant questions remain about how smoking and quitting affect cardiovascular diseases and mortality. A new study published in the journal "PLOS Medicine" closely examines the relationship between smoking intensity and quitting with a wide range of cardiovascular health outcomes.

Risks of Smoking

Tobacco use causes more than eight million deaths each year. Smoking doubles the risk of cardiovascular diseases and can shorten lifespan by five years or more due to its harmful effects on the heart. In recent years, researchers have also uncovered additional links between smoking and cardiovascular diseases, such as atrial fibrillation and other heart rhythm disorders, according to "News Medical".

Previous research has shown that the benefits of quitting smoking are almost immediate. Among younger adults, the excess mortality risk decreases by 90 to 95 percent within the first three years after quitting, preventing a loss of about five years of life. Within ten years after quitting, the excess mortality risk is nearly eliminated, reclaiming almost a decade of expected lifespan.

While many smokers attempt to quit, others reduce the number of cigarettes they smoke. As a result, the percentage of individuals smoking fewer than ten cigarettes daily increased from 16 percent in 2005 to 27 percent in 2014, and the proportion of non-daily smokers grew from 19 percent to 23 percent during the same period.

However, the relationship between low-intensity smoking (two to five cigarettes daily) and cardiovascular diseases remains unclear, and the duration related to quitting that yields benefits has not been quantified. The current study aimed to shed light on this important area.

Study of Smoking and Cardiovascular Health Outcomes

The study utilized data from 22 prospective studies, analyzing years of smoking, daily cigarette count, and years of quitting against multiple health outcomes, including heart attacks, strokes, heart disease, heart failure, atrial fibrillation, and mortality from any of these causes.

The researchers followed the study participants for up to 20 years, and the study included data from over 323,000 adults, with over 176 cases of death analyzed.

Who Was Most at Risk?

The average age of participants was about 60 years, with 76 percent of them being women. Overall, 14 percent were current smokers, 36.4 percent had never smoked, and 49 percent were former smokers. Current smokers averaged about 20 cigarettes daily, while former smokers had quit for an average of 21 years.

Current smokers consistently faced higher risks for all outcomes compared to former smokers and never-smokers.

Among men, smoking was associated with a 74 percent increased risk of cardiovascular diseases, including heart attacks and strokes; among women, the risk more than doubled. Mortality from all causes was 117 percent higher among male smokers and 143 percent higher among female smokers compared to those who had never smoked. Individuals smoking one cigarette a day or less still faced an increased risk for most health outcomes (except for stroke and atrial fibrillation) compared to never-smokers.

Smoking two to five cigarettes daily was associated with an increased risk for all health outcomes. For instance, the risk of atrial fibrillation was 26 percent higher, and the risk of heart failure was 57 percent higher. Similarly, the risk of death from cardiovascular diseases increased by 57 percent, and mortality from all causes rose by 60 percent.

People smoking 11 to 15 cigarettes daily faced even higher risks, with the risk of cardiovascular diseases increasing by 87 percent and the risk of death from any cause rising by 130 percent compared to those who had never smoked.

The increase in risk was highest during the first twenty years of smoking, though it continued to rise thereafter. A similar curve was observed for daily cigarette count, with risk sharply rising to about 20 cigarettes daily before the curve began to stabilize.

Benefits of Quitting Smoking

The most significant drop in risk occurred during the first decade after quitting, but benefits continued to accumulate more gradually in the long term. After 20 years of quitting, former smokers were about 80 percent less at risk than current smokers, a benefit particularly evident among those who quit at younger ages.

The highest risk was among individuals who had smoked for many years and had quit recently.

Early quitting saves lives

Smoking, even at very low levels, increases the risk of cardiovascular diseases. Quitting leads to a significant reduction in the risk of cardiovascular diseases and death shortly thereafter, with declines continuing over the subsequent two decades after quitting.