Table 4. Comparison of the risk of pulmonary hospitalized infection during the first year of follow-up between treatment groups of RA patients.

	No. of events	PY	Crude IR per 100 PY (95% CI)	Crude HR (95% CI)	p value	Adjusted HR* (95% CI)	p value
Total (n = 1596)	50	1239	4.0 (3.1–5.3)	-	-	-	-
Etanercept (n = 413)	16	312	5.1 (3.1–8.4)	2.33 (0.96–5.67)	0.06	1.65 (0.67–4.09)	0.28
Infliximab (n = 335)	8	262	3.1 (1.5–6.1)	1.40 (0.51–3.85)	0.52	2.07 (0.75–5.76)	0.16
Adalimumab (n = 264)	12	202	5.9 (3.4–10.5)	2.67 (1.06–6.85)	0.002	4.43 (1.72–11.37)	0.002
Abatacept (n = 189)	7	143	4.9 (1.9–9.3)	2.21 (0.78–6.32)	0.14	1.63 (0.56–4.72)	0.37
Tocilizumab (n = 395)	7	319	2.2 (1.0–4.6)	reference	-	reference	-
Age	-	-	-	-	-	1.03 (1.01–1.06)	0.018
Body mass index < 18.5	-	-	-	-	-	2.90 (1.56–5.39)	0.001
Prednisolone use†
≥ 7.5 mg/day	-	-	-	-	-	2.49 (1.36–4.54)	0.003
NIDDM	-	-	-	-	-	2.45 (1.30–4.61)	0.005
HRCT-proven chronic lung disease	-	-	-	-	-	3.61 (1.94–6.73)	< 0.001

*Cox regression analysis was performed to compare treatment effect of each biological agent on pulmonary hospitalized infection, after adjustment for possible confounders. The possible confounders included age, sex, BMI, smoking history, RA duration, RA stage III/IV, RA class 3/4, previous use of biological agents, concurrent use of MTX, concurrent use of prednisolone, and comorbid diseases (chronic kidney disease, diabetes mellitus, and chronic lung disease). All confounders listed in the table are factors identified as the true confounders and included in the final Cox model.

^†Referent to no use of prednisolone.

RA, rheumatoid arthritis; PY, person-year; IR, incidence rate; HR, hazard ratio; 95% CI, 95% confidence interval; NIDDM, non-insulin-dependent diabetes mellitus; HRCT, high-resolution computed tomography