Table 4. Sensitivity analysis of adjusted hazard ratios (95% CI) stratified by follow-up period.

	Tonsillectomy		Non-Tonsillectomy		HR	95% C.I.
	N	No. of IBS	N	No. of IBS
Follow-up duration
≤3 yearsa	1300	11	2600	15	1.51	0.69–3.30
>3 yearsb	1104	16	2216	17	1.98	0.99–3.95

a: Adjusted for age, gender, hypertension, hyperlipidemia, chronic liver disease, cardiovascular disease, autoimmune disease, and corticosteroids.

b: Adjusted for age, gender, hypertension, chronic liver disease, diabetes, COPD, cancer, and corticosteroids.