Table 1.

Studies reporting findings on sleep EEG features and sleep subjective features in ASD patients.

Author, Year, Country	ASD Group					Control Group			PSG/EEG Features	Subjective Measures
	n (% Male)	Mean Age (Age Range)	Diagnosis	Diagnostic Tools	Inclusion/Exclusion Criteria	Type	n (% Male)	Mean Age (Age Range)
Elia, 2000, Italy [25]	17 (100%)	10.36 years (5.7–16.8 years)	Autistic disorder (DSM-IV)	CARS	Inclusion criteria in AD patients: Diagnosis of AD according to the DSM-IV guidelines Exclusion criteria in AD patients: Interictal paroxysmal activity in the EEG Other pathological conditions (fragile X syndrome, epilepsy, cerebellar abnormalities at brain MRI) Drug period of 6 months preceding and during the study	fragile XTD	7 (100%) 5 (100%)	9.92 years (8.25–12 years) 9.22 years (7.17–11.58 years)	2 PSG with one adaptation night	-
Malow, 2006, USA [26]	21(85.7%)	- (4–10 years)	Autism, pervasive developmental disorder, Asperger’s disorder (DSM-IV)	ADOS	Inclusion criteria in ASD patients: Clinical diagnosis of ASD from psychologist or clinicians verified by the ADOS Exclusion criteria in ASD patients: Psychotropic medications History of epileptic seizures or mental retardation	TD	10 (80%)	(4–10 years)	2 consecutive nights of video monitoring combined with EEG and PSG with 21 EEG channels	Sleep diaries CSHQ
Miano, 2007, Italy [27]	31 (90.3%)	9.53 years (3.7–19 years)	Autistic disorder (DSM-IV)	CARS	Inclusion criteria in ASD patients: Diagnosis of autism according to DSM-IV and a score on the CARS > 30 Mental retardation Drug-free period for at least 2 weeks before the study began Exclusion criteria in ASD patients: Presence of neurological focal signs, seizures or paroxysmal EEG abnormalities Presence of craniofacial abnormalities, fragile X syndrome or other chromosome abnormalities Presence of obesity and no history of snoring	TD	18 (50%)	age-matched	Overnight PSG recording after one adaptation night. The PSG montage includes at least 3 EEG channels (including C3 and C4 in particular)	Sleep Questionnaire
Bruni, 2007, Italy [28]	10 autism (90%) 8 Asperger syndrome (87.5%)	autism: 11.9 ± 2.5 years (7–15 years) Asperger syndrome: 12.7 ± 2.6 years (7–15 years)	Autism (DSM-IV) Asperger syndrome (DSM-IV)	CARS	Inclusion criteria in patients with AS: Clinical diagnosis of AS verified by the ADOS Inclusion criteria in patients with autism: Diagnosis of autism according to DSM-IV and a score on the CARS > 30 Presence of mental retardation Exclusion criteria in patients with AS: History of serious physical health problems, epileptic seizures or mental retardation Presence of obesity or snoring Taking medications Exclusion criteria in patients with autism: Drug-free period from at least 2 weeks before the study began Presence of neurological focal signs, seizures or paroxysmal EEG abnormalities Other medical conditions associated with autism Obesity and history of snoring Exclusion criteria in control patients: Anamnesis of neuropsychiatric disorders Current axis I or axis II psychiatric disorders Complaints of sleep problems.	TD	12 (41.6%)	12.6 ± 3.7 years (7–15 years)	PSG overnight The PSG montage included at least 8 EEG channels (Fp1, Fp2, C3, C4, T3, T4, O1, O2) All recordings started at the patients’ usual bedtime and continued until spontaneous awakening.	Sleep Questionnaire PDSS
Goldman, 2009, USA [29]	27 psASD (88.9%) 15 gsASD: (93.3%)	PS: 5.8 years GS: 5.9 years	ASD (DSM-IV)	ADOS	Inclusion criteria in ASD children: Clinical diagnosis of ASD confirmed by the ADOS Exclusion criteria in ASD children: History of epilepsy Intellectual disability Psychotropic medications	TD	16 (75%)	6.9 years	Two consecutive nights of PSG with 21-channel EEG and actigraphy monitoring	PCQ CSHQ
Ming, 2009, USA [30]	23 (82.6%)	6 years (3–15 years)	autistic disorder, PDD-NOS, Asperger’s disorder (DSM-IV)	ASD ADI-R, ADOS-G	Inclusion criteria in ASD patients: Clinical diagnosis of ASD according to DSM-IV and confirmed by ADI-R and ADOS-G Complaints of sleep related problems Exclusion criteria in ASD patients: Presence of focal neurological signs Exclusion criteria in control patients: No known developmental or chronic illness with the exception of acute reactive airway disease and/or allergy in 7 children No history of neurological disorders and no acute illness including reactive airway disease or allergy at time of PSG study	TD	23 (65.2%)	5 years (3–12 years)	PSG for 2 consecutive nights with standard four channel EEG for PSG	Sleep Questionnaires
Giannotti, 2010, Italy [31]	22 NRegASD (75%) 18 RegASD (80%)	5.5 years 5.10 years	autistic disorder (DSM-IV)	ADI-R, ADOS-G	Inclusion criteria in autistic groups: Clinical diagnosis of autism according to the DSM-IV and confirmed by the ADOS-G and ADI-R NVIQ > 50 Exclusion criteria in autistic groups: Presence of other serious neurological, psychiatric, bipolar disorder or medical conditions Presence of obesity and history of snoring Altered hematological screening Presence of infections, inflammatory or allergic reactions for at least 6 months prior to the beginning of the study	TD	12 (75%)	5.8 years	Overnight PSG including at least 11 EEG channels (Fp1, Fp2, C3, C4, Cz, P3, P4, T3, T4, O1, O2) for 2 consecutive nights	CSHQ
Buckley, 2010, USA [32]	60 (82%)	4.81 years (2.24–13.11 years)	Autism (DSM-IV)	ADOS, ADI-R	Inclusion criteria in patients with autism: Clinical diagnosis of Autism according to DSM-IV and confirmed by ADI-R and ADOS-G	developmental delay TD	13 (54%) 15 (73%)	4.29 years (2.69–7.11 years) 3.69 years (1.35–5.84 years)	Overnight PSG with 21 lead electroencephalogram montage	CSHQ
Tessier, 2015, Canada [33]	13 (100%)	10.23 years (6–13 years)	hfASD(DSM-IV-TR)	ADI, ADOS	Inclusion criteria in patients with autism: Diagnosis based on ADOS and ADI-R and confirmed by DSM-IV criteria Exclusion criteria in patients with autism: Sleep disturbances (sleep apnea, PLMS) Atypical EEG patterns Medications (except for 3 children who were treated with methylphenidate) FSIQ < 75	TD	13 (100%)	10.23 years (7–12 years)	Recordings took place on 2 consecutive nights in individual bedrooms using bilateral central, frontal and occipital EEG leads (C3, C4, F3, F4, O1, O2)	Sleep diary
Tessier, 2015 Canada [34]	13 (100%)	10.23 years (6–13 years)	hfASD(DSM-IV-TR)	ADI-R, ADOS	Inclusion criteria in patients with autism: Diagnosis based on ADOS and ADI-R and confirmed by DSM-IV criteria Exclusion criteria in patients with autism: Sleep disturbances (sleep apnea, PLMS) Atypical EEG patterns Medications (except for 3 children who were treated with methylphenidate) FSIQ < 75	TD	13 (100%)	10.23 years (7–12 years)	Recordings took place on 2 consecutive nights in individual bedrooms using bilateral central, occipital and parietal EEG leads (C3, C4, O1, O2, P7, P8)	Sleep diary
Lambert, 2015 Canada [35]	11 (100%)	10.27 years (6–13 years)	hfASD(DSM-IV)	ADI-R, ADOS	Inclusion criteria in patients with autism: Diagnosis based on ADOS and ADI-R and confirmed by DSM-IV criteria Exclusion criteria in patients with autism: Diagnosis of other axis-I disorders Medical disorders other than autism Taking medications Sleep problems FSIQ < 70	TD	13 (100%)	10.23 years (7–12 years)	Participants spent two consecutive nights in the sleep laboratory, the first night served for adaptation to recording conditions. All PSG data reported were recorded during the second night. The electrodes that have been used are not specified	CSHQ
Sahroni, 2015, Japan [36]	8 (87.5%)	10.23 years (7–12 years)	Autistic disorder (DSM-IV)		Inclusion criteria in patients with autism: Diagnosis based on DSM-IV criteria Exclusion criteria in patients with autism: Presence of illness Taking medications	TD	8 (62.5%)	6.14 ± 2.19 years	Both groups were given some sedative before EEG recordings to make subjects sleep in a short time of period (10–15 min) 19 electrodes were placed according to the 10–20 international system	___
Maski, 2015, USA [37]	22 (86%)	11.3 years (9–16 years)	ASD (DSM-IV)	ADOS, ADI R	Inclusion criteria in ASD group: Diagnosis based on the ADOS and ADI-R NVIQ not more than 1.33 standard deviations below the mean Exclusion criteria in all participants: Significant hearing or vision loss Metabolic disease, neurogenetic disorders or co-occurring neurological disorders A previously diagnosed sleep disorder An unstable chronic medical condition such as asthma, diabetes, cystic fibrosis or cardiac disease Exclusion criteria in TD group: Sleep disorder, psychiatric disorder or neurodevelopmental condition Use of medications known to affect sleep, memory or daytime vigilance	TD	20 (90%)	12.3 years (9–16 years)	Home PSG recordings with seven channels of EEG (F1, F2, C3, Cz, C4, O1, O2)	CSHQ
Lehoux, 2017, Canada [38]	13 (100%)	10.23 years (6–13 years)	hfASD(DSM-IV)	ADI R	Inclusion criteria in ASD patients: Diagnosis based on ADOS and ADI-R and confirmed by DSM-IV criteria Exclusion criteria in ASD patients: Taking medications interacting with the central nervous system Intellectual disability Reported poor sleep Presence of other diagnosis besides ASD	TD	13	10.23 years (7–12 years)	PSG montage included 7 EEG channels (F3, F4, C3, P3, P4, O1, O2).	Sleep diary
Aathira, 2017, India [39]	71(90.3%)	5.3 ± 1.8 years (3–10 years)	ASD (DSM-IV)		Inclusion criteria in ASD group: Diagnosis based on DSM-IV criteria Exclusion criteria in both groups: Chronic systemic disorders known to interfere with sleep Exclusion criteria in ASD group: Presence of tuberous sclerosis, fragile X syndrome and Down syndrome	TD	65 (61.5%)	5.7 ± 1.6 years (3–10 years)	Single overnight PSG	CSHQ
Vite, 2018, Messico [40]	10 (100%)	8.2 years (6–10 years)	ASD, level 1 (DSM-IV and DSM-V)		Inclusion criteria in ASD group: Having a multiaxial diagnosis of ASD according to DSM-IV and DSM-V criteria Exclusion criteria in TD group: Presence of sleep disturbances Taking medications Previous diagnosis of a chronic disease Health issues that modifysleep at the time of registration Failure to complete 2 nights of PSG Exclusion criteria in ASD group: Failure to complete 2 nights of PSG	TD	7 (100%)	8.3 years (6–10 years)	2 eight-hour PSG were performed for 2 consecutive nights. The referrals for night 1 were: C3, C4, O2, O1 The referrals for night 2 were: F3, F4, C3, C4, T3, T4, P3, P4, O1, O2	-
Farmer, 2018 USA [41]	85 (84%)	2–6 years	Autistic disorder (DSM-IV-TR)	ADI, ADOS	Inclusion criteria in patients with autism: Diagnosis based on ADOS and ADI-R and confirmed by DSM-IV criteria Inclusion criteria in DD group: Cognitive score at least 1.5 SDs below the mean No diagnosis of ASD Inclusion criteria in TD group: No evidence of personal or first-degree family history of autism or significant DD	TD DD	29 (72%) 21 (62%)	2–6 years 2–6 years	Overnight video-EEG	-
Page, 2019, USA [42]	7 (71.4%)	21.8 months (13–30 months)	ASD (DSM-5)	FYI, M-CHAT-R/F, ADOS-2	Inclusion criteria in ASD group: High risk for ASD screened with the FYI and the M-CHAT-R/F and confirmed with the ADOS-2 Inclusion criteria in both groups: Sleeping between 8 and 14 hr at night One nap per day Free of known sleep disorder Free of medications Exclusion criteria in both groups: Reported history of presence of epilepsy Neurological/metabolic or developmental disability other than ASD Severe visual or motor impairment	TD	13 (38.4%)	21.8 months (13–30 months)	EEG was recorded during a daytime nap (average duration of 78 min) with a 124- or 128-channel high density EEG electrode net	Sleep diary
Fletcher, 2019, UK [43]	20 (80%)	125.55 months	autism	GARS	Inclusion criteria in ASD group: GARS-AI scores ≥ 71 Exclusion criteria in ASD group: Diagnosis of co-occurring conditions (i.e., dyslexia) Inclusion criteria in TD group: Not a sibling of a child with ASD GARS-AI < 55 No diagnosed psychological disorder	TD	34 (50%)	118.94 months	Home PSG with a montage of six EEG (F3, F4, C3, C4, O1, O2)	CSHQ
Arazi, 2019, Israel [44]	29 (72.4%)	4.6 years (1.9–7.8 years)	autism (DSM-5)	ADOS	Inclusion criteria in ASD group: Diagnosis based on ADOS and confirmed by DSM-V criteria 5 children with ASD were excluded from the final analysis due to poor PSG evaluationExclusion criteria in TD group: Snoring Sleep problems such as bedwetting, daytime sleepiness Neurological, psychiatric or developmental disorders	TD	23 (65.2%)	5.3 ± 1.5 years	PSG with 6 EEG electrodes (C3, C4, O1, O2, A1, A2)	CSHQ

AD: Autistic Disorders; ADI-R: Autism Diagnostic Interview–Revised; ADOS: Autism Diagnostic Observation Schedule; ADOS-2: Autism Diagnostic Observation–2nd Edition; ADOS-G: Autism Diagnostic Observation Schedule–Generic; AS: Asperger syndrome; ASD: autism spectrum disorder; CARS: Childhood Autism Rating Scale; CSHQ: Children’s Sleep Habits Questionnaire; DD: developmental delay; DSM-IV: Diagnostic and Statistical Manual of Mental Disorders, 4th edition; DSM-5: Diagnostic and statistical manual of mental disorders (5th ed.); EEG: electroencephalogram; FSIQ: full-scale Intelligence Quotient; FYI: first year inventory; GARS: Gilliam Autism Rating Scale; gsASD: good sleepers ASD; hfASD: high functioning ASD; ICD-10: International Statistical Classification of Diseases and Related Health Problems, 10th revision; IQ: Intelligence Quotient; M-CHAT-R/F: Modified checklist for autism in toddlers, revised with follow-up; MRI: magnetic resonance imaging; NVIQ: Non Verbal Intelligence Quotient; NRegASD: not regressive ASD; PCQ: Parental Concerns Questionnaire; PDD-NOS: pervasive developmental disorder not otherwise specified; PDSS: pediatric daytime sleepiness scale; PIQ: Performance Intelligence Quotient; PLMS: periodic leg movement syndrome; psASD: poor sleepers ASD; PSG: polysomnography; RegASD: regressive ASD; TD: typically-developing.