Lifestyle factors including higher body mass index and smoking are associated with changes in left-atrial size and function

1. In this prospective cohort study, lifestyle behaviours, especially higher body mass index (BMI) and smoking, are associated with measurable changes in left-atrial size and function. 

Evidence Rating Level: 1 (Excellent) 

Left atrial size and function are strong predictors of atrial fibrillation (AF), stroke, and mortality, and even subtle changes in these measures signal higher vulnerability. Several modifiable lifestyle factors, such as obesity, alcohol use, smoking, physical activity, and coffee consumption, may influence left atrial remodelling and contribute to AF development. However, the mechanisms underlying this are not well understood. To address this gap, this prospective cohort study evaluates the associations between modifiable lifestyle behaviours and left atrial structures, and whether these atrial differences help explain lifestyle-associated AF risk. The cohort included 37,701 participants, and the median time between the lifestyle questionnaires and the MRI was 8.9 years (IQR 7.4-10). A higher body mass index (BMI), more vigorous physical activity, and greater alcohol consumption were each associated with larger left atrial volumes and lower left atrial emptying fractions. In contrast, greater cumulative smoking exposure was associated with smaller atrial volumes and reduced emptying fraction, while coffee intake showed no meaningful relationship with any left atrial measure. Larger left atrial volumes were associated with a progressively higher risk of developing AF, while a lower left atrial emptying fraction also predicted a greater risk. About 25% of the link between higher BMI and future AF was explained by changes in the left atrium, specifically, larger maximal volume (25%), larger minimal volume (28%), and lower emptying fraction (26%). These findings suggest that common lifestyle behaviours contribute to adverse left-atrial remodelling, which in turn accounts for a substantial portion of the increased AF risk associated with obesity and smoking. 

Click here to read this study in Journal of the American Heart Association

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