Abstract 12830: Significant Smoking Reduction and the Risk of Cardiovascular Disease (CVD): Prospective Results From the Framingham Heart Study

Abstract

Smoking cessation reduces CVD risk, but whether significant reduction ( > 50%) in cigarettes per day (CPD) decreases CVD risk is unclear. Some prior studies have reported no benefit but are limited by incomplete capture of smoking exposure due to few smoking assessments or short follow-up. We used Framingham Heart Study data to quantify CVD risk benefits of smoking reduction. We included participants attending at least two exams: 3642 Original cohort starting with their fourth exam (1954-1958) and 3582 Offspring cohort starting with their first exam (1971-1975). Participants were free of CVD at baseline and were followed through 2016 for incident CVD. We updated smoking and other variables every 2 (Original) and 4 (Offspring) years, pooling cohorts for analysis. Using extended Cox regression, we compared CVD risk among 4 categories of person-time: current smoking with significant reduction (CPD reduced by > 50%); current smoking without significant reduction (maintained, increased, or reduced by < 50%); former smokers (quit during follow up); and never smokers. Models were adjusted for sex and time-varying covariates (age, CPD, years reduced, pack-years smoked, and other traditional CVD risk factors). Relative to the Offspring, the Original cohort was older (51 vs 44) and had a larger proportion of current smokers (49% vs 36%) but smoked fewer CPD (19 vs 23). During a median follow up of 27 years, 2327 CVD events occurred (4.3% among significant reducers). Compared to current smoking without significant reduction, significant reduction was associated with lower CVD risk (HR [95% CI]: 0.76 [0.58, 0.99]). After excluding smokers who increased CPD, the effect was similar (HR=0.80 [0.60, 1.08] p=0.14). Significant reduction was associated with higher CVD risk compared to quitting smoking (1.57 [1.24, 2.01]) and never smoking (1.45 [1.12, 1.87]). Significant CPD reduction is associated with lower CVD risk compared to current smoking without significant reduction, but with higher CVD risk compared to quitting and never smoking. These findings incorporate extensive lifetime smoking history, including changes in smoking rate, and provide evidence for public health messaging that, while cessation is preferred, smoking reduction may also decrease CVD risk.