Table 2. Incidence of osteoporosis in patients with and without ankylosing spondylitis (AS).

	Patients with AS		Patients without AS		Rate ratio (95% CI)	P value
	No. of osteoporosis	Per 1,000 person-years	No. of osteoporosis	Per 1,000 person-years
Total	214	10.21	408	4.70	2.17 (1.83–2.57)	< 0.001
Age
≥ 65	77	53.36	164	23.34	2.29 (1.72–3.02)	< 0.001
< 65	137	7.02	244	3.06	2.29 (1.85–2.84)	< 0.001
Sex
Male	88	6.51	133	2.38	2.73 (2.06–3.60)	< 0.001
Female	126	16.93	275	8.89	1.91 (1.53–2.36)	< 0.001
Follow-up
0–1	55	1747.14	59	747.21	2.34 (1.59–3.43)	< 0.001
1–5	69	200.99	154	128.76	1.56 (1.16–2.09)	0.003
5–10	67	15.09	143	7.90	1.91 (1.41–2.57)	< 0.001
≥ 10	23	1.43	52	0.77	1.85 (1.08–3.07)	0.019

CI indicates confidence interval