Research in the past has shown that cigarette smoking increases heart disease risk, but the exact relationship between smoking intensity and health outcomes remained unclear, especially for low- intensity smoking. Studies reported inconsistent timeframes, ranging from 2 to 29 years, for how long former smokers need to remain smoke-free before their risk approaches that of never-smokers.
A new study published in the journal PLOS Medicine looked to understand the cardiovascular risks of low-intensity smoking and the long-term benefits of quitting. The researchers analyzed data from 22 prospective cohort studies with 323,826 adults (76 per cent women), following participants for up to 19.9 years and documenting over 125,000 deaths and 54,000 cardiovascular events.
Low-intensity smoking (2 to 5 cigarettes per day) was associated with a 50 per cent higher risk of cardiovascular disease and a 60 per cent higher risk of all-cause mortality compared to never smoking. The most substantial risk reduction across all outcomes occurred within the first decade following smoking cessation. However, continued risk diminution persisted beyond this initial period. Even occasional or low- intensity smoking significantly increases cardiovascular and mortality risks.
The research concluded that there should be complete smoking cessation at younger ages rather than reducing the amount of smoking. Smoking cessation is associated with substantial risk reduction that begins immediately upon quitting and continues with a steep decline in risk during the first 10 years following smoking cessation.
Source: PLOS Medicine, 2025
