Table 2.

Incidence rates (per 1,000 person-years) and incidence rate ratios (IRR) of atrial fibrillation (AF)

Outcome definition	Rheumatoid arthritis (N=20,852)			Non-rheumatoid arthritis (N=104,260)			IRR (95% CI)
	Cases (n)	Person-years, mean (SD)	Rates (95% CI)	Cases (n)	Person-years, mean (SD)	Rates (95% CI)
	AF (inpatient)	160	1.93 (1.5)	4.0 (3.4–4.7)	574	2 (1.6)		2.8 (2.6–3.0)	1.4 (1.2–1.7)
AF (inpatient) and anticoagulants *	77	1.93 (1.5)	1.9 (1.5–2.4)	297	2 (1.6)	1.5 (1.3–1.6)	1.3 (1.0–1.7)
AF (inpatient and outpatient) and anticoagulants *	114	1.93 (1.5)	2.8 (2.4–3.4)	511	2 (1.6)	2.5 (2.3–2.7)	1.1 (0.9–1.4)

CI: confidence interval, SD: standard deviation

^*: a dispensing of anticoagulants within 30 days after the diagnosis date