Table 2.

Length of Treatment Episodes in Relation to Therapeutic Regimen, Years^*

Disease and therapy**	N	Average duration of follow-up, years
		Duration on anti-TNF-α therapy	Duration on nonbiologic comparison	Duration on neither non-biologic comparison nor anti-TNF-α therapy	Total duration of follow-up (exit minus entry)
RA
Initiated anti-TNF-α	21,260	1.48	0.12	0.84	2.44
Did not switch	18,177	1.49	0	0.75	2.24
Switched to non-biologic	3,083	1.44	0.83	1.35	3.63
Did not initiate anti-TNF-α	10,651	0	1.08	1.61	2.68
PsO, PsA, AS
Initiated anti-TNF-α	4,368	1.21	0.18	0.65	2.04
Did not switch	3,431	1.19	0	0.53	1.72
Switched to non-biologic	937	1.27	0.80	1.13	3.20
Did not initiate anti-TNF-α	5,836	0	0.97	1.61	2.58
IBD
Initiated anti-TNF-α	3,329	0.96	0.24	1.23	2.43
Did not switch	2,163	0.95	0	1.03	1.98
Switched to non-biologic	1,166	0.97	0.68	1.63	3.28
Did not initiate anti-TNF-α	6,078	0	1.07	1.44	2.51
Total***
Initiated anti-TNF-α	28,941	1.39	0.14	0.84	2.37
Did not switch	23,877	1.40	0	0.14	2.14
Switched to non-biologic	5,064	1,37	0.78	1.37	3.43
Did not initiate anti-TNF-α	17,483	0.00	1.06	1.57	2.63

^*Restricted to patients with propensity scores in the overlapping region.

^**Patients with multiple autoimmune diseases are shown in multiple disease categories.

^***Under Total, each patient is shown in the table only once. The 5,064 patients contributing person-years to both the anti-TNF-α group and the non-biologic comparison group are shown with the anti-TNF-α group.