Association between serum free thyroxine concentration and atrial fibrillation

Area of Science:

• Endocrinology
• Cardiology
• Geriatrics

Background:

• Previous research suggests a link between subtle thyroid function changes and atrial fibrillation (AF) risk.
• Thyroid dysfunction prevalence and its association with AF in older populations require further investigation.

Purpose of the Study:

• To investigate the relationship between thyroid function and the presence of atrial fibrillation (AF) in individuals aged 65 and older.
• To determine if thyroid hormone levels are independently associated with AF in an aging cohort.

Main Methods:

• A population-based study included 5860 subjects aged 65+, excluding those with treated thyroid dysfunction or prior hyperthyroidism.
• Thyroid function was assessed via serum free thyroxine (T4) and thyrotropin (TSH) levels.
• Atrial fibrillation (AF) was identified using resting electrocardiogram.

Main Results:

• Subclinical hyperthyroidism was found in 2.2% of subjects, with a higher AF prevalence (9.5%) compared to euthyroid individuals (4.7%).
• Higher serum free T4 concentrations were significantly associated with the presence of AF, even within the euthyroid group.
• Logistic regression identified free T4 levels, increasing age, and male sex as independent predictors of AF.

Conclusions:

• Subclinical hyperthyroidism is biochemically associated with atrial fibrillation (AF) detected by electrocardiogram.
• Elevated serum free T4 levels, even in euthyroid individuals with normal TSH, are independently associated with AF in older adults.