Sleep and cognitive problems in patients with attention-deficit hyperactivity disorder

Figures & data

Table 1 Demographic and cognitive characteristics

Characteristic	ADHD (N=37)	Controls (N=32)	P-value
Age, mean (SD) (years)	8.7 (2.1)	9.3 (1.9)	0.244
Sex, male (%)	100	100	NS
IQ, mean (SD)	98.6 (16.6)	104.8 (14.9)	0.111
Verbal IQ	97.1 (14.3)	101.6 (13.7)	0.190
Performance IQ	100.9 (18.1)	106.0 (18.1)	0.244
MFFT, mean (SD)
Response error (percentile)	57.6 (26.5)	32.3 (22.2)	<0.001*
Response error (counts)	12.3 (7.4)	7.6 (4.6)	0.003*
Response latency (percentile)	69.8 (22.1)	44.0 (23.2)	<0.001*
Response latency (s)	108.7 (51.8)	177.0 (67.4)	<0.001*

Note:

* P<0.05 as determined by independent t-test.

Abbreviations: ADHD, attention-deficit hyperactivity disorder; IQ, intelligence quotient; MFFT, Matching Familiar Figures Test; NS, not significant; SD, standard deviation.

Table 2 Sleep parameters of ADHD patients and controls

	ADHD (N=37)	Controls (N=32)	P-value
Total sleep time (minutes)	461.1 (36.7)	448.3 (39.5)	0.168
Sleep latency (minutes)	16.2 (19.7)	6.6 (6.2)	0.01*
Sleep efficiency (%)	83.0 (4.6)	85.2 (6.3)	0.108
Wake after sleep onset (minutes)	57.4 (23.2)	30.7 (13.7)	<0.001*
Fragmentation index (%)	16.7 (4.5)	10.3 (4.4)	<0.001*

Note:

* P<0.05 as determined by independent t-test.

Abbreviation: ADHD, attention-deficit hyperactivity disorder.

Table 3 Correlations between cognitive functions and sleep parameters in ADHD patients

	Age	IQ	Verbal IQ	Performance IQ	MFFT–RE (percentile)	MFFT–RE (counts)	MFFT–RL (percentile)	MFFT–RL (time)	TST	SL	SE	WASO
IQ	−0.033
Verbal IQ	−0.115	0.879**
Performance IQ	−0.051	0.906**	0.647**
MFFT–RE (percentile)	−0.230	−0.265	−0.253	−0.185
MFFT–RE (counts)	0.378*	−0.256	−0.198	−0.193	0.963**
MFFT–RL (percentile)	−0.155	0.086	0.072	0.103	0.570**	0.588**
MFFT–RL (time)	0.072	−0.218	−0.154	−0.237	−0.480**	−0.493**	−0.858**
TST	−0.249	0.011	0.093	−0.081	0.427*	0.434**	0.382*	−0.366*
SL	0.225	−0.492**	−0.566**	−0.367*	−0.226	−0.261	−0.269	0.341*	−0.382*
SE	−0.192	0.328	0.222	0.291	0.217	0.153	0.205	−0.331	0.530**	−0.503**
WASO	−0.022	−0.305	−0.242	−0.257	0.517*	0.179	0.040	0.094	−0.303	0.279	−0.638**
FI	0.018	0.040	−0.018	0.110	0.439*	0.456**	0.399*	−0.215	0.011	−0.167	−0.196	0.356*

Notes:

* P<0.05 as determined by Pearson’s correlation test.

** P<0.001 as determined by Pearson’s correlation test.

Abbreviations: ADHD, attention-deficit hyperactivity disorder; FI, fragmentation index; IQ, intelligence quotient; MFFT–RE, Matching Familiar Figures Test–response error; MFFT–RL, Matching Familiar Figures Test–response latency; SL, sleep latency; SE, sleep efficiency; TST, total sleep time; WASO, wake after sleep onset.

Table 4 Factors associated with fragmentation index

Variables	Beta	t	P-value
Age	0.240	1.393	0.194
IQ	−3.161	−0.586	0.571
Verbal IQ	2.464	0.808	0.438
Performance IQ	1.342	0.489	0.635
MFFT
Reaction error (percentile)	0.943	2.662	0.024*
Reaction error (counts)	−0.270	−0.796	0.445
Response latency (percentile)	1.309	0.630	0.543
Response latency (time)	0.223	0.586	0.571
TST	−0.408	−1.668	0.126
SL	−0.205	−0.708	0.495
SE	−0.138	−0.431	0.675
WASO	0.621	2.767	0.020*

Note:

* P<0.05 as determined by multiple linear regression.

Abbreviations: IQ, intelligence quotient; MFFT, Matching Familiar Figures Test; SE, sleep efficiency; SL, sleep latency; TST, total sleep time; WASO, wake after sleep onset.