Table 4

  Rates and incidence rate ratios (IRR) of atrial fibrillation in study cohort by level of thyroid stimulating hormone (TSH) with normal free thyroxine concentration

EuthyroidismSubclinical hyperthyroidism
NormalHigh normalReduced TSHSuppressed TSH
TSH level (mIU/L)0.4–5.00.2–0.40.1–0.2<0.1
Rate of atrial fibrillation
No of events15 652623155280
Time at risk (1000 PY)3000.073.913.821.1
Incidence rate (No/1000 PY):
 Crude4.98.411.213.3
 Age adjusted 8.08.88.910.3
Incidence rate ratio (95% CI)*1.00 (reference)1.12 (1.03 to 1.21)1.16 (0.99 to 1.36)1.41 (1.25 to 1.59)
Attributable risk percent†111429

PY=person years. NA=not applicable.

*Risk estimates are adjusted for sex, age, calendar year, Charlson comorbidity index, and socioeconomic status.

†Attributable risk percent = (IRR−1)/IRR×100.