Background and Purpose- Metabolic syndrome (MetS), a prothrombotic state, is associated with an increased risk of atrial fibrillation (AF) and stroke. The CHA₂DS₂-VASc score does not account for the MetS components of prehypertension, prediabetes mellitus, abdominal obesity, elevated triglycerides, and low HDL (high-density lipoprotein). Data are limited on the association of MetS with stroke in AF, independent of CHA₂DS₂-VASc variables. Our aim was to identify MetS components associated with ischemic stroke in participants with AF in the ARIC study (Atherosclerosis Risk in Communities). Methods- We included 1172 participants with incident AF within 5 years of measurement of MetS components. MetS was defined by ATP criteria and International Diabetes Federation criteria. Incident ischemic stroke was physician adjudicated. Multivariable Cox proportional hazards regression was used to assess the association of MetS components with stroke. Results- After a median follow-up of 14.8 years, there were 113 ischemic stroke cases. Of the individual MetS components, low HDL was borderline associated with increased stroke risk (hazard ratio, 1.48 [95% CI, 0.99-2.21]) after adjustment for CHA₂DS₂-VASc variables while the remaining MetS variables were not associated with stroke risk. The presence of ≥3 components of MetS was not significantly associated with ischemic stroke after adjustment for CHA₂DS₂-VASc variables (hazard ratio, 1.38 [95% CI, 0.91-2.11]). The risk of stroke increased by 13% for each additional component of MetS; however, this association was borderline significant (hazard ratio, 1.13 [95% CI, 0.99-1.28]). Conclusions- The presence of MetS was not significantly associated with ischemic stroke after adjustment for CHA₂DS₂-VASc variables. Consideration of MetS is unlikely to improve stroke prediction in AF.

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