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The association between hyperthyroidism and risk of atrial fibrillation (AF) is well described. In contrast, whether hypothyroidism results in increased risk of AF remains unclear. Hypothyroidism is associated with obesity, heart failure and PR interval prolongation, all of which have been related to longitudinal AF risk. We investigated the relation between hypothyroidism and the 10-year risk of AF in a community-based cohort.
We examined 6,653 Framingham Heart Study participants, excluding participants missing thyroid stimulating hormone (TSH), TSH <0.5 mIU/L (hyperthyroid), or with prevalent AF. TSH was stratified as <5.0, 5.0-10.0, 10.0-20.0, ≥ 20.0 and by quartiles. We examined the association between TSH and 10-year risk of AF using age- and sex-adjusted, multivariable Cox proportional hazards analysis.
Following exclusions, 5,106 participants (52% women, mean age 57±12) were eligible for the current analysis. During the 10-year follow-up, we observed 280 cases of incident AF. We determined that the association between a 1-standard deviation (SD) increase in TSH and AF did not reach statistical significance (Hazard Ratio [HR]: 1.08, 95% confidence interval [CI]: 0.95-1.22, p = 0.23). Using TSH<5.0 as a referent, we found no significant association between hypothyroidism and 10-year AF risk employing TSH categorized as 5-10.0 (HR: 1.44, 95% CI: 0.89-2.33, p = 0.14), 10-20 (HR: 0.61, 95% CI: 0.23-1.65, p = 0.33) or ≥ 20.0 (HR: 1.02, 95% CI: 0.32-3.19, p = 0.98). Furthermore, comparing the highest (TSH>2.5) to lowest (TSH<1.3) quartiles of TSH in our cohort, the association between hypothyroidism and 10-year risk of AF was also not significant (HR: 1.25, 95% CI: 0.91-1.73, p = 0.17). Excluding participants on thyroid replacement therapy (n=323) did not alter these findings. A post-hoc power analysis identified our study would have required HR 1.26 per 1-SD increase in TSH to achieve 80% power.
In our community-based study, we did not identify a significant association between hypothyroidism and 10-year risk of incident AF. A study with a larger number of events may have improved power to examine the relation of hypothyroidism to AF.
Poster Sessions, Expo North
Sunday, March 10, 2013, 3:45 p.m.-4:30 p.m.
Session Title: Arrhythmia Outcomes and Quality Assessment
Abstract Category: 4. Arrhythmias: AF/SVT
Presentation Number: 1245-114
- 2013 American College of Cardiology Foundation