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

	Euthyroidism			Subclinical hyperthyroidism
	Normal	High normal		Reduced TSH	Suppressed TSH
TSH level (mIU/L)	0.4–5.0	0.2–0.4		0.1–0.2	<0.1
Rate of atrial fibrillation
No of events	15 652	623		155	280
Time at risk (1000 PY)	3000.0	73.9		13.8	21.1
Incidence rate (No/1000 PY):
Crude	4.9	8.4		11.2	13.3
Age adjusted	8.0	8.8		8.9	10.3
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†		11		14	29

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.