Modifiable Lifestyle Factors, Left Atrial Indices, and Atrial Fibrillation

Left atrial (LA) size is an important determinant of atrial fibrillation (AF) risk and predicts stroke and death. The relationship between common lifestyle factors, LA characteristics, and relationships with incident AF remain largely unknown.

In this cohort study, we evaluated 37 701 UK Biobank participants without prevalent AF and with cardiac magnetic resonance imaging data. Body mass index was measured by study personnel, while other lifestyle factors were obtained from baseline questionnaires. Cardiac magnetic resonance imaging was performed using a uniformly applied protocol and analyzed using automated methods to determine LA volumes and emptying fraction (EF).

The magnetic resonance imaging was performed a median 8.9 (interquartile range, 7.4-10) years after the baseline lifestyle factor assessment. In multivariable analyses, a larger body mass index, greater physical activity intensity, and more alcohol intake were each significantly associated with larger LA volumes and smaller LA EFs. In contrast, cumulative pack-years of smoking were linked to smaller LA volumes and LA EFs. Coffee consumption exhibited no significant associations. Larger LA maximal and minimal volumes and a lower LA EF statistically mediated 25%, 28%, and 26% of the association between an increased body mass index and risk of incident AF, respectively, evaluated in separate models. A lower LA EF mediated 27% of the smoking and AF association.

Common lifestyle factors are associated with unfavorable LA size and function, mediating about a quarter of the AF risk associated with obesity and smoking. Lifestyle-related structural LA changes may contribute to AF risk.