Serum ferritin levels in children with attention deficit hyperactivity disorder and tic disorder

Table 1 Characteristics of patients and control subjects

	HC	ADHD	TD	ASD
n	1997	1565	1694	93
(M/F)	(979/1018)	(1317/248)	(1282/412)	(83/10)
%	49.02/50.98	84.15/15.85	64.2/35.8	89.25/10.75
Age	8.57 ± 2.28	7.92 ± 1.85	7.61 ± 2.03	6.14 ± 2.88
Sex
Male	74.34 ± 51.19a	36.82 ± 20.64	35.72 ± 20.15	31.42 ± 18.58
Female	69.08 ± 52.64a	35.64 ± 18.56	34.54 ± 22.12	27.42 ± 13.73
SF	71.66 ± 51.99	36.63 ± 20.32	35.43 ± 20.64	30.99 ± 18.11
F (%)	8.61a	8.37a	11.04a	15.05a

^aP < 0.05.

HC: Healthy control; ADHD: Attention deficit hyperactivity disorder; TD: Tic disorder; ASD: Autism spectrum disorders; SF: Serum ferritin; F: Incidence of low serum ferritin.

Table 2 Description of the average distribution of age and serum ferritin level

Grouping	Mini	Max	Mean	SD	Skewness	Kurtosis	95%CI lower	95%CI upper
HC age	5.00	12.00	8.57	2.28	-0.03	-1.26	8.47	8.67
HC SF	1.30	200.00	71.66	51.99	0.76	-0.51	69.38	50.63
ADHD age	5.00	12.00	7.92	1.85	0.47	-0.65	7.83	8.01
ADHD SF	2.60	148.60	36.63	20.32	1.53	3.42	35.62	37.64
TD age	5.00	12.00	7.61	2.03	0.49	-0.76	7.52	7.71
TD SF	2.90	262.70	35.43	20.64	2.66	15.31	34.45	36.41
ASD age	1	14.00	6.14	2.88	0.47	0.35	5.55	6.73
ASD SF	4.7	89.6	30.98	18.11	1.25	1.41	27.26	34.71

HC: Healthy control; ADHD: Attention deficit hyperactivity disorder; TD: Tic disorder; ASD: Autism spectrum disorders; SF: Serum ferritin.

Table 3 The β of attention deficit hyperactivity disorder/tic disorder for the level of serum ferritin among children

	Model 1		Model 2		Model 3
	β	P	β	P	β	P
Among children with ADHD
ADHD	-0.107	< 0.001	-0.107	< 0.001	-0.110	< 0.001
Age			0.011	< 0.001	0.011	< 0.001
Sex					0.021	< 0.001
Among children with TD
TD	-0.113	< 0.001	-0.108	< 0.001	-0.114	< 0.001
Age			0.001	< 0.001	0.010	< 0.001
Sex					0.021	< 0.001

Model 1 was not adjusted for any other variables; Model 2 was further adjusted for age; Model 3 was further adjusted for age and sex. ADHD: Attention deficit hyperactivity disorder; TD: Tic disorder.

Table 4 Odds ratio of attention deficit hyperactivity disorder/tic disorder for low serum ferritin among children

	Model 1, OR (95%CI)	Model 2, OR (95%CI)	Model 3, OR (95%CI)
Among children with ADHD
ADHD	0.94 (0.74-1.19)	0.90 (0.71-1.15)	0.82 (0.63-1.06)
Age		0.68 (0.46-1.01)	0.68 (0.46-1.01)
Sex			1.22 (0.94-1.58)
Among children with TD
TD	0.97 (0.77-1.22)	0.91 (0.72-1.15)	0.99 (0.78-1.28)
Age		0.65 (0.93-1.56)	0.65 (0.95-1.53)
Sex			1.38 (1.08-1.75)

ADHD: Attention deficit hyperactivity disorder; TD: Tic disorder; OR: Odds ratio. Model 1 was not adjusted for any other variables. Model 2 was further adjusted for age. Model 3 was further adjusted for age and sex.

Table 5 Comparison of serum ferritin in different age groups

Age (yr)	HC	ADHD	TD
5	63.15 ± 52.54	28.77 ± 17.54	29.73 ± 21.55
6	65.05 ± 48.64	31.66 ± 16.38	32.68 ± 16.54
7	75.24 ± 55.18	33.78 ± 19.16	33.99 ± 19.48
8	79.05 ± 53.37	37.93 ± 20.34	36.63 ± 16.76
9	77.88 ± 52.77	43.27 ± 22.41	41.92 ± 23.44
10	77.10 ± 49.96	43.59 ± 21.15	40.74 ± 18.28
11	68.65 ± 49.32	42.36 ± 24.06	38.17 ± 25.55
12	66.85 ± 52.22	32.66 ± 18.77	39.16 ± 28.08
F	3.651	14.206	9.381
P	0.001	0.000	0.000

HC: Healthy control; ADHD: Attention deficit hyperactivity disorder; TD: Tic disorder.