Analysis finds even low-intensity smokers have higher risk of heart disease and death

An analysis of data from almost two dozen long-term studies finds that even low-intensity smokers have a substantially higher risk of heart disease and death compared to people who never smoked, even years after they quit. Michael Blaha of the Johns Hopkins Ciccarone Center for Prevention of Cardiovascular Disease, USA, and colleagues report these findings November 18^th in the open-access journal PLOS Medicine.

Previous research has shown that smoking cigarettes increases a person's risk of developing cardiovascular disease, but the exact relationship between how heavily a person smokes and their risks is still unclear, especially for low-intensity smokers. Today, more people are smoking fewer cigarettes, but it's still important to understand the cardiovascular risks and long-term benefits of quitting, even for individuals who aren't smoking a pack a day.

Blaha's team analyzed data from more than 300,000 adults enrolled in 22 longitudinal studies – which involve following groups of individuals over time – for up to 19.9 years. In that time, they documented more than 125,000 deaths and 54,000 cardiovascular events, such as heart attacks, strokes and heart failure. The analysis showed that even very low-intensity smoking, defined as two to five cigarettes per day, was associated with a 50% higher risk of heart failure and a 60% higher risk of death from any cause, compared to never smoking. A person's risk of cardiovascular events dropped most substantially in the first decade after quitting smoking and continued to decrease over time. However, even up to three decades later, former smokers may still exhibit higher risk compared to those who never smoked.

Considering that even occasional or very low-intensity smoking significantly increases a person's risk of cardiovascular disease and death, the researchers conclude that quitting smoking at younger ages is the best way to decrease your risk, rather than reducing the number of cigarettes smoked each day. These findings reinforce established public health guidelines – that smokers should quit as early as possible instead of just cutting back – and emphasize the importance of smoking prevention programs.

The authors add, "This is one of the largest studies of cigarette smoking to date using the highest quality data in the cardiovascular epidemiology literature. It is remarkable how harmful smoking is – even low doses of smoking confer large cardiovascular risks. As far as behavior change, it is imperative to quit smoking as early in life as possible, as the among of time passed since complete cessation from cigarettes is more important prolonged exposure to a lower quantity of cigarettes each day."