Table 3. Age- and sex-specific incidence of childhood intussusception in South Korea.

Age (yr)	New cases of intussusception					Incidence (per 105 person-years)					p-value	M/F incidence ratio
	Boys	Girls	Total	Fraction (%)	Accumulation (%)	Boys	Girls	Total	IRR	IRR 95% CI
0	5,519	3,751	9,270	30.45	30.45	226.0	162.6	195.2	35.18	34.01–36.40	<0.0001	1.39
1	6,338	3,697	10,035	32.96	63.41	245.7	151.8	200.1	36.07	34.88–37.30	<0.0001	1.62
2	4,024	1,967	5,991	19.68	83.09	154.7	80.2	118.6	21.37	20.59–22.18	<0.0001	1.93
3	1,826	838	2,664	8.75	91.84	69.5	33.9	52.2				2.05
4	827	306	1,133	3.72	95.56	31.1	12.3	21.9				2.53
5	391	143	534	1.75	97.32	14.5	5.7	10.2				2.55
6	169	62	231	0.76	98.08	6.1	2.4	4.3				2.54
7	111	47	158	0.52	98.59	3.9	1.8	2.9				2.19
8	58	24	82	0.27	98.86	2.0	0.9	1.5	Reference (≥3 yr)			2.24
9	64	12	76	0.25	99.11	2.1	0.4	1.3				4.92
10	38	12	50	0.16	99.28	1.2	0.4	0.8				2.91
11	38	14	52	0.17	99.45	1.2	0.5	0.8				2.49
12	29	7	36	0.12	99.57	0.8	0.2	0.6				3.77
13	35	8	43	0.14	99.71	1.0	0.3	0.6				3.96
14	20	6	26	0.09	99.79	0.5	0.2	0.4				3.00
15	16	9	25	0.08	99.88	0.4	0.3	0.3				1.60
16	18	7	25	0.08	99.96	0.5	0.2	0.3				2.30
17	9	4	13	0.04	100.00	0.2	0.1	0.2				2.01
Total	19,530	10,914	30,444	100.00		34.8	21.2	28.3				1.64

The age- and sex-specific incidence was calculated by dividing the number of new cases in each age and sex group by the age- and sex-specific population size of children aged <18 years from 2007 through 2017.

M: male, F: female, IRR: incidence rate ratio, CI: confidence interval.

IRR, 95% CI, and p-values were calculated using Poisson regression.