Left atrial enlargement (LAE) with vs without atrial fibrillation (AF) was not found to be associated with greater cognitive decline over a 5-year period, according to study results published in the Journal of the American Heart Association.

AF is generally associated with a greater risk for dementia and cognitive decline. However, it remains unclear whether LAE, a critical substrate of AF, is also associated with a decline in cognitive function. In this longitudinal study, the data from 3391 patients with and without AF who were enrolled in the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS) were analyzed. The ARIC-NCS community-based prospective cohort study was initiated in 1989 to identify risk factors for the development of cardiovascular diseases in the general population. After the baseline examination, patients completed 5 additional examinations between 1990 and 2017 consisting of cognitive testing, echocardiography, and electrocardiography. 

Patients were stratified into 4 groups for analysis. Group 1 included patients without AF or LAE (n=2842), group 2 included patients with AF only (n=107), group 3 included patients with LAE only (n=337), and group 4 included patients with both AF and LAE (n=105). LAE was defined as a left atrium volume index ≥34 mL/m2 using echocardiography, and prevalent AF was determined using 12-lead electrocardiogram assessments from visits 1 through 5, as well as hospitalization discharge codes.

The mean age of patients in the cohort was 74.4±5.1 years, 59% of whom were women, and 21% of whom were black. The prevalence of LAE was 13%, and the prevalence of AF was 6%. Compared with group 1, only group 4 (comorbid AF and LAE) had lower global cognition (Z score, -0.24; 95% CI, -0.38 to -0.10) at the 5-year visit in a ross-sectional analysis. Group 2 (AF only) was the only group in which the decline in global cognition (Z score, -0.13; 95% CI, -0.21 to -0.06) were greater compared with group 1 (no AF or LAE).

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Study limitations include the possibility that some participants with asymptomatic AF may have been missed, as the condition was identified based on hospitalization discharges and electrocardiograms. In addition, the potential effects of AF duration were not accounted for, the fact that LAE was defined from a single echocardiographic measurement at visit 5, potentially contributing to type 2 error, and the sole evaluation of LA size, not function. ”Although LAE with AF was significantly associated with lower cognitive function in cross‐sectional analysis, LAE, with or without AF, was not associated with greater cognitive decline over 5 years, highlighting the importance of evaluating longitudinal cognitive function,” concluded the study authors. “Future studies should have longer follow‐up and evaluate left atrium function.”

Reference

Zhang MJ, Norby FL, Lutsey PL, et al. Association of left atrial enlargement and atrial fibrillation with cognitive function and decline: the ARIC-NCS [published online November 26, 2019]. J Am Heart Assoc. doi: 10.1161/JAHA.119.013197