Table 1 Summary of all included studies with sample characteristics regarding sex differences & PROGRESS-Plus-related results

1. Armitage R. (1995); Sleep; USA;

Texas; Dallas;

Sleep laboratory

(1) Analyze EEG parameters & interhemispheric variances by sleep stages & sex

(2) Clinical trail

(3) Two-time assessment

(4) a. NR

    b. No meds except oral/implant CCs

    c. Pre-study alc & caff restriction; keep sleep–wake pattern for 5 d

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. First-degree relative w psy d/o

(1) 22 (11 M/11F)

(2) NR

(3) M (25.6 ± 4.2 years)

F (24.8 ± 3.9 years)

(4) 50

(5) NR

(6) None

(7) Emerging & early adulthood

(1) δ (0.5– < 4 Hz),

θ (4– < 8 Hz),

α (8– < 12 Hz),

σ (12– < 16 Hz),

β (16– < 32); standalone EEG

(2) Sleep efficiency

(3) 2-way ANOVA/sex

(1) No sex diff in δ, θ, & α across sleep stages. Overall δ pwr during NREM stages 2–4 was ↑ in F. No sex diff in δ pwr during REM

(2) NR

(3) Sex diff in EEG during sleep were minimal

2. Armitage R. et al. (2000);

Sleep;

USA; Texas;

Dallas; Sleep laboratory

(1) Compare δ activity in NREM btw depressed & healthy participants by sex

(2) Comparative study

(3) Two-time assessment

(4) a. NR

    b. NR

    c. 2 continuous d of sleep w/o disruption

    d. No family Hx of Axis I d/o

(5) a. Shift worker

    b. Current Axis I/sleep d/o

    c. Substance abuse w/i 12 months pre-study

    d. NR

(1) 23 (15 M/8F)

(2) NR

(3) 22–40 years

M (27.1 ± 5.9 years)

F (30.9 ± 6.2 years)

(4) 65

(5) NR

(6) Age

(7) Emerging & early adulthood

(1) δ (0.5– < 4 Hz); standalone EEG

(2) Sleep efficiency, latency

(3) R-measures analyses of variance ANOVAs/sex, age, psychiatric status; mean, SD by sex

(1) Normal control F had a ↑ δ power than M, but results were not statistically sign; F showed 4.6% ↑ δ amp but results were not statistically sign (NREM 2–4)

(2) Sex diff is likely to ↓ w ↑ age. F showed strong age effect w ↓ pwr & ampl; for M this effect was not stat sign

(3) The amount or amp of δ activity showed sign group by sex interactions

3. Baker F. C. et al. (2012);

J Sleep Res;

Australia; Victoria; Abbotsford; Sleep laboratory

(1) Explore regional & sex diff in sleep & EEG changes in adolescents over 6–8 mos

(2) Comparative study

(3) Two-time assessment

(4) a. Adolescents 11–14 y

    b. NR

    c. Keep sleep–wake pattern for 5 d

    d. NR

(5) a. NR

    b. CNS d/o; lifetime psy/neuro/sleep d/o; loss of consciousness > 30 min

    c. NR

    d. NR

(1) 33 (18 M/15F)

(2) 15

(3) 11–14 years

M (12.7 ± 0.9 years)

F (12.4 ± 0.7 years)

(4) 55

(5) Place of residence, Tanner stage

(6) Age

(7) Childhood & adolescence

(1) δ (0.3– < 4 Hz),

θ (4– < 8 Hz),

α (8– < 12 Hz),

σ (12– < 15 Hz),

β1 (15– < 23 Hz); standalone EEG

(2) Sleep efficiency, latency

(3) Two-way R-measures ANOVAs/sex, age

(1) No sign sex effects were found for θ pwr; no sign sex effects or interaction for δ pwr or amp. No sign effects of age, derivation, sex, or interactions for α, σ, or β pwr

(2) Sign main effects of age were observed for δ activity δ pwr & amp ↓ in the occipital region w ↑ age during adolescence

(3) θ, α, & σ pwr in NREM & REM sleep at the occipital site ↓ over time, w no sex diff in these age-related changes

4. Campbell I. G. et al. (2005);

Sleep;

USA; California; Davis; Participant’s home

(1) Study the timing of NREM δ EEG pwr decline & pubertal maturation btw sexes

(2) Longitudinal study, semi-annual for 4 yrs

(3) Two-time assessment

(4) a. NR

    b. NR

    c. Keep sleep–wake pattern for 5 d/no naps

    d. NR

(5) a. NR

    b. Hx of head injury/lifetime psy/neuro d/o

    c. NR

    d. NR

(1) 70 (35 M/35F)

C9: 32 (16 M/16F)

C12: 38 (19 M/19F)

(2) NR

(3) 1st recording mean 9.31 ± 0.04 (C9), 12.33 ± 0.04 (C12);

2nd recording mean 9.83 ± 0.05 (C9), 12.80 ± 0.04 (C12)

(4) C9: 50

C12: 50

(5) Tanner stage

(6) Age

(7) Childhood & adolescence

(1) δ (0.3–3 Hz),

3–4 Hz,

θ (4–6 Hz; 6–8 Hz)

α (8–12 Hz),

σ (12–15 Hz),

β (15–23 Hz, 23–30 Hz),

30–50 Hz*; standalone EEG

(2) Sleep efficiency, density

(3) Post hoc t tests/sex, age; correlation coefficients/ delta power density, Tanner stage

*Freqs inferred from study Table 4 & text in results section

(1) M in C12 had sign ↑ δ pwr density than F due to a > δ-wave amp. C12 M had ↑ α & β pwr density in the first recording period & ↑ θ, α, σ pwr densities in the second recording period. No sex diff in δ pwr density or amp were observed in C9

(2) Sex diff present in C12 indicates the possibility of F beginning adolescent brain maturation earlier than M. Tanner stage was not correlated w δ activity

(3) C12 M had 37% ↑ δ pwr per min than F, while C9 showed no sex diff. Similar results found six months later

5. Campbell I. G. et al. (2012);

PNAS;

USA; California; Davis; Participant’s home

(1) Compare adolescent δ decline in EEG data from 9- & 12-yr-old M & F

(2) Longitudinal study, semi-annual for 6 or 7 yrs

(3) Two-time assessment

(6) a. NR

    b. NR

    c. Keep sleep–wake pattern for 5 d

    d. NR

(7) a. NR

    b. Current psy/neuro d/o

    c. Sleep disturbance

    d. NR

(1) 67 (33 M/34F)

C9: 30 (15 M/15F)

C12: 37 (18 M/19F)

(2) 16

(3) 9 years, 12 years

(4) 50

(5) Place of residence, race

(6) Age, Tanner stage

(7) Childhood & adolescence, emerging & early adulthood

(1) δ (1–4 Hz),

θ (4–8 Hz); standalone EEG

(2) Sleep latency, efficiency

(3) Gompertz equation/sex, age, Tanner stage

(1) F experienced the most rapid ↓ in δ pwr at 12.53 (± SE 0.19) yrs, 1.21 (± 0.25) yrs earlier than M. Sex diff sign & explaining 32% of the variance. The rate of ↓ was similar btw sexes. No sign diff btw sexes in the upper asymptote of the delta curve or in the change from the upper to lower asymptotes

(2) As age ↑ δ pwr ↓, & adolescents peak pubertal maturation was positively correlated w δ pwr decline

(3) The rate of ↓ varied sign among participants, w no correlation observed btw the rate of ↓ & other factors. Delayed maturation did not lead to a faster decline

6. Carrier J. et al. (2001); Psychophysiology;

USA; Pennsylvania; Pittsburgh; Sleep laboratory

(1) Investigating the impact of age & gender on sleep EEG pwr spectral density in middle age participants

(2) Cross-sectional study

(3) Five-time assessment

(4) a. NR

    b. Healthy

    c. NR

    d. No Hx of personal/family psy/neuro/sleep/medical d/o

(5) a. NR

    b. Any medical condition; on sleep meds; obese (BMI > 27)/considerable wt loss; AHI > 10/PLMAI > 10

    c. No alc/drugs ≥ 14 d pre-study

    d. First-degree relative w prev seizures/psy d/o

(1) 100 (53 M/47F)

(2) NR

(3) 20–60 yrs

(4) 53

(5) Occupation

(6) Age

(7) Emerging & early adulthood, middle & late adulthood

(1) δ (1–4 Hz),

θ (NR),

σ (NR),

α (NR),

β (NR)

spindle (NR); standalone EEG

(2) Sleep density

(3) Multivariate modeling/sex, age

(1) F had ↑ spectral pwr density in δ, θ, low α bins in NREM1 (0.25 -9.00 Hz), NREM2 (0.25–10.00 Hz), NREM3 (0.25–9.00 Hz), NREM4 (0.25–10.00 Hz). F had ↑ spindle pwr density from 14.25 to 16.00 Hz in all four NREM periods compared to M

(2) ↑ age is associated w fragile sleep wake system manifested through ↓ pwr spectral density in SW sleep & ↑ in high freq power

(3) No sign interactions were found btw age & sex, suggesting that the aging process does not differently affect M & F btw 20 & 60 yrs old

7. Carrier J. et al. (2011); Eur J Neurosci; Canada; Quebec; Montreal; Sleep laboratory

(1) Study how age, sex, & topography impact SW characteristics in young & middle-aged participants

(2) Longitudinal study

(3) Multiple assessment

(4) a. 2 age groups: 20–30 & 41–60

    b. < 4 on BDS

    c. NR

    d. Had PSG screen

(5) a. Night work

    b. On sleep altering meds; psy/neuro d/o Hx

    c. Smoking; Transmeridian travel 3 mos pre-study; sleep disturbance/sleep duration of ≤ 7/ ≥ 9 h; perimenopausal

    d. F’s using hormonal CCs/HRT

(1) 87 (44 M/43F)

a. Young: 48 (26 M/22F)

b. Middle-aged: 39 (18 M/21F)

(2) NR

(3) Young: 20–30 years (23.3 ± 2.4 years)

Middle-aged: 41–60 years (61.9 ± 4.6)

(4) Young: 54

Middle-aged: 46

(5) NR

(6) Age

(7) Emerging & early adulthood, middle & late adulthood

(1) δ (1–4 Hz); standalone EEG

(2) Sleep efficiency, latency

(3) Two-way ANOVA/sex, age

(1) F exhibited ↑ SW amp & slope compared to M

(2) ↑ in age is correlated w ↓ SW amp & slope

(3) Compared to M, F showed ↑ SW amp, shorter SW freq, shorter positive phase duration. Older adults also showed slower SW density & amp

8. Dijk D. J. et al. (1989); Sleep;

Netherlands; Groningen Province; Groningen; Sleep laboratory

(1) Identify sex diff by comparing sleep in young adult & published sleep deprivation EEG data

(2) Cross-sectional study

(3) Two-time assessment

(4) a. NR

    b. NR

    c. No sleep complaints

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 28 (13 M/15F)

(2) NR

(3) 19–27 years

M (23.5 years)

F (21.9 years)

(4) 46

(5) NR

(6) None

(7) Emerging & early adulthood

(1) EEG freq (0.25–15 Hz); standalone EEG

(2) Sleep latency

(3) Student’s t test/sex

(1) In NREM sleep, F had ↑ pwr densities in δ freq compared to M, except in the 12 & 13 Hz bins. In REM sleep, F showed ↑ pwr densities in all freq bins except the 9 & 10 Hz bins

(2) Sex diff may not be associated w differential aging process due to its presence in participants in their 20s

(3) Published data on sleep deprivation effects on EEG pwr spectra didn't indicate a common mechanism for sleep deprivation effects & sex diff in sleep EEGs

9. Dorokhov B. V. et al. (2024);

Chronobiol. Int.; Russia; Moscow; Sleep laboratory

(1) Understand the paradoxical relationship between sex & objective & subjective sleep quality using EEG during nap

(2) Cross-sectional

(3) Three-time assessment

(4) a. NR

    b. NR

    c. NR

    d. NR

(5) a. ≤ 18 & > 23 yrs; shift worker

    b. Hx of mental/sleep d/o; current mild cold

    c. Complaints about poor phys condition & functioning; missed class in the 2 wks pre-study; crossed time zones 1 month pre-study; irregular sleep–wake schedule (1 + h diff in wkday bedtime, frequent sleep reduction)

    d. Pregnant/breastfeeding

(1) 80 (40 M/40F)

(2) NR

(3) M (20.4 ± 1.57 years)

F (20.25 ± 1.14 years)

(4) 50

(5) Education

(6) None

(7) Early adulthood

(1) δ (1–4 Hz),

θ (5–8 Hz),

α (9–12 Hz),

σ (13–16 Hz); standalone EEG

(2) Spectral EEG markers of sleep & wake drives, sleep stage durations

(3) 1st & 2nd PCA EEG spectrum, Pearson r, rANOVA/sex

(1) F had ↑ spectral pwr density across all sleep stages for δ, θ, α, σ

(2) NR

(3) F's stronger sleep drives linked to ↑ δ activity; sleep complaints may vary

10. Feinberg I. et al. (2006);

Am J Physiol Regul Interg Comp Physiol; USA; California; Davis; Participant’s home

(1) Investigate the relationship btw δ decline, puberty, growth, sleep patterns, sex & age

(2) Controlled clinical trial

(3) Two-time assessment

(4) a. NR

    b. No psy/neuro/medical d/o; on meds affecting CNS

    c. No sleep complaints; keep sleep–wake pattern for 5 d/no naps

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. First-degree relative w major psy d/o

(1) 69 (34 M/35F)

C9: 31 (15 M/16F)

C12: 38 (19 M/19F)

(2) NR

(3) 9 years, 12 years

C9: (9 years ± 3 mos)

C12: (12 years ± 3 mos)

(4) C9: 48

C12: 50

(5) Place of residence, race, Tanner stage

(6) Age, Tanner stage

(7) Childhood & adolescence

(1) δ (0.3–3 Hz),

1–4 Hz; standalone EEG

(2) Sleep efficiency

(3) ANOVA/sex, age, recording session; mixed effect analyses/ δ pwr density, age, height, weight, BMI, Tanner stage

(1) NREM δ pwr density did not alter from ages 9–11, w no sex diff. It ↓ by 25% btw 12 & 14, w F showing lower levels, indicating an earlier decline

(2) The ↓ in δ pwr density is strongly linked to both age & sexual maturation stage. Tanner stage, height, weight, or BMI was unrelated to δ pwr density once the age effect was removed

(3) In C9, there were no sign effects of recording session or sex on δ pwr density, & no interaction btw recording & sex. In C12, δ pwr density ↓ across four recordings & was sign ↓ in F than M, though the rate of ↓ was similar btw sexes from ages 12 to 14

11. Fukuda N. et al. (1999);

Psychiatry Clin Neurosci;

Japan; Hokkaido; Sapporo; Participant’s homes

(1) Explore sex effects on SWA in middle aged & elderly participants by spectral analysis

(2) Cross-sectional study

(3) Three-time assessment

(4) a. NR

    b. No sign medical; No meds

    c. NR

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 16 (8 M/8F)

(2) NR

(3) 54–72 years

M (61.5 ± 4.66 years)

F (62.38 ± 6.65 years)

(4) 50

(5) NR

(6) None

(7) Middle & late adulthood

(1) δ (0.5–4 Hz); standalone EEG

(2) Sleep efficiency, latency

(3) Mann–Whitney U test/sex

(1) F have longer SWS durations & ↑ rate of SWA than M. The total amount of δ band spectral pwr is ˃ in F compared to M. F exhibit clearer periodic fluctuations in δ band pwr throughout the night

(2) Middle aged & elderly F showed a sign ↑ pwr level for both freq δ bands

(3) Sign sex diff exist in SWS, w middle-aged & elderly F showing a more conservative SWS-generating mechanism compared to M

12. Hejazi S. N. et al. (2024);

J Psychiatr Res;

USA; Bethesda; NIH Clinical Centre

(1) Examine relationship between sex, age, & sleep patterns w low & high δ pwr

(2) Randomized control trial

(3) Two-time assessments

(4) a. 18–65 yrs

    b. No psychotropic meds for 2 + wks (5 + for fluoxetine & 3 + for aripiprazole); absence of Axis I d/o

    c. NR

    d. No first-degree relative w DMS-IV Axis I d/o

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 24 (8 M/16F)

(2) NR

(3) 20–56 years (33.75 ± 11.02 years)

(4) 33

(5) NR

(6) Age

(7) Early & middle adulthood

(1) Low δ (0.5–2 Hz),

high δ (2–4 Hz); standalone EEG

(2) TST, sleep efficiency, WASO

(3) Mann–Whitney U test/sex

(1) No sign sex diff in δ spectral pwr density btw healthy M & F

(2) NR for healthy participants

(3) NR for healthy participants

13. Kluge M. et al. (2010); PNEC;

Germany; Bavaria; Munich;

Sleep laboratory

(1) Study sex diff in ghrelin’s impact on sleep & the secretion of GH & cortisol in elderly participants

(2) RCT (PL-controlled)

(3) One-time assessment

(4) a. NR

    b. Healthy

    c. No caff, alc, naps

    d. NR

(5) a. NR

    b. Any sleep disturbance/d/o; Any meds/HRT

    c. Sleep duration of ≤ 6 h/ ≥ 9 h/ transmeridian flight 3 mos pre-study

    d. Depressive symptoms

(1) 20 (10 M/10F)

(2) NA

(3) 60–70 years

M (64 ± 2.2 years)

F (63 ± 2.9 years)

(4) 50

(5) NR

(6) None

(7) Middle & late adulthood

(1) δ (0.5–4 Hz),

θ (4.5–8 Hz),

α (8.5–12 Hz),

σ (12.5–16 Hz),

β (16–20 Hz); standalone EEG

(2) Sleep density, efficiency

(3) Mean, SD by sex

(1) PL F had a ↑ pwr than M for δ; PL M had ↑ pwr for β. No diff in θ, α, or σ pwr

(2) GH affects sleep in elderly M but not F resembling findings in young participants

(3) In M, δ pwr sign ↑, while α & β pwr ↓ after GH compared to PL injection during the first half of the night. In both sexes, ghrelin caused comparable ↑, secretion patterns of GH & cortisol. GH caused a sign ↑ of stage 2, SWS, NREM, while ↓ of stage 1 & REM in elderly M. GH did not affect sleep in postmenopausal elderly F

14. Latta F. et al. (2005);

Sleep;

USA; Illinois; Chicago; Sleep laboratory

(1) Examine sex effects on sleep stages & EEG spectral pwr in older participants

(2) Clinical trial

(3) Two-time assessment

(4) a. NR

    b. No obese participants; normal lab test; no Hx of psy/sleep/neuro/endocrine d/o; no meds/HRT

    c. Non-smoking; < 5 on GDS; > 25 on FMSE

    d. F 1 + y past menopause w no hot flash

(5) a. Shift workers

    b. Diabetes/glucose intolerance

    c. 2 + caff drinks per d; shift workers/transmeridian travel 4 weeks pre-study

    d. NR

(1) 20 (10 M/10F)

(2) 10

(3) M (59 ± 2 years)

F (63 ± 2 years)

(4) 50

(5) Place of residence

(6) None

(7) Middle & late adulthood

(1) δ (0.5–4 Hz),

α (8.5–12 Hz); standalone EEG

(2) Sleep latency, sleep period, TST, sleep maintenance

(3) 2-way ANOVA/sex

(1) Absolute δ & α activity was ↑ in F than M, irrespective of sleep stage. No sex diff in relative δ or α activity in either NREM or REM

(2) As age ↑ there is an ↑ age related changes in sleep architecture that occur & differ btw sexes

(3) Older F show ↓ δ activity than M. The sex difference in δ activity is more pronounced in REM than NREM sleep, w stable REM δ activity throughout the night in both sexes. When normalized for REM, F have ↓ NREM δ activity than M. Blood sampling ↓ total sleep time, sleep maintenance, SWS, & δ activity more in F. In F, but not M, blood sampling ↓ REM δ activity, which strongly correlates w NREM δ activity

15. Luo X. et al. (2024);

Front Psychol;

NR; Sleep laboratory

(1) To investigate the relationship between age, gender, & EEG functional connectivity

(2) Retrospective study

(3) Two-time assessment

(4) a. NR

    b. No sleep-related meds

    c. NR

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. Incomplete data

(1) 135 (56 M/79F)

(2) 13

(3) 25–101

M (57.89 ± 21.34 years)

F (54.39 ± 21.65 years)

(4) 41

(5) NR

(6) Age

(7) Early, middle & late adulthood

(1) δ (0.5–4 Hz),

θ (4–8 Hz),

α (8–13 Hz),

β (13–30 Hz),

Spdl (11–16 Hz),

Sawtooth (3–7 Hz); standalone EEG

(2) Sleep staging

(3) Machine learning models (SVM, RF, KNN)/sex, age; one-way ANOVA/sex, age

(1) F had ↑ FC in α, β, & spdl bands across sleep stages; no sex diff in δ, θ, & sawtooth connectivity across sleep stages

(2) Diff in functional connectivity was seen btw diff age groups

(3) Enhanced β & spdl connectivity may support better memory consolidation in F

16. Ma J. et al. (2011);

J Clin Sleep Med;

USA; NR;

Sleep laboratory

(1) Study gaboxadol’s effect on NREM sleep EEG patterns in transient insomnia using pwr spectral analysis

(2) RCT (PL-controlled)

(3) One-time assessment

(4) a. 18–64 years

    b. NR

    c. NR

    d. NR

(5) a. NR

    b. Sleep/psy d/o; > 5 on PSQI/ > 12 on ESS; sleep apnea/PLMD; sleep duration 6.5–9 h; bedtime btw 21:00–24:00 ≥ 4 times a wk; latency < 30 min

    c. MSLT < 10 min; excessively sleepy participants

    d. NR

(1) 822 (314 M/508F)

(2) NA

(3) 18–64 years

M (28.78 ± 8.21 years)

F (31.76 ± 10.70 years)

(4) 38

(5) NR

(6) None

(7) Emerging & early adulthood, middle & late adulthood

(1) δ (0.5–4.25 Hz),

θ (4.25–8 Hz),

α (8–12 Hz),

σ (12–15 Hz),

β (15– 32.5 Hz),

Spdl (11–14 Hz); EEG via PSG

(2) Sleep latency, efficiency

(3) Linear mixed-effects model/sex, frequency, & their interactions

(1) At baseline, F showed sign ↑ power spectral densities in low-freq (1–10 Hz) & high spdl/low β freq (14–18 Hz) ranges. High β (19–32 Hz) power spectral densities were > in F but the diff was not statistically sign compared to M. From the figure, sigma power spectral densities were > in F from 14–15 Hz but no sign sex differences from 12 to < 14

(2) NR for placebo prior to intervention

(3) NR for placebo prior to intervention

17. Markovic A. et al. (2020);

Sci Rep;

Switzerland; Bern;

Bern; Participant’s homes

(1) Examine sex diff in sleep EEG power & coherence across freq bands in NREM & REM in adolescents

(2) Clinical Trial

(3) Two-time assessment

(4) a. 9–14 years

    b. NR

    c. NR

    d. Born after 30th week of pregnancy

(5) a. NR

    b. NR

    c. NR

    d. Poor quality EEG data

(1) 61 (30 M, 31F)

(2) NR

(3) 9–14 years

M (12.83 ± 0.75)

F (12.12 ± 1.67)

(4) 49

(5) Tanner stage

(6) Age, Tanner stage

(7) Childhood & adolescence

(1) δ (1–4.6 Hz),

θ (4.8–7.8 Hz),

α (8–10.8 Hz),

σ (11–16 Hz),

β1 (16.2– 20 Hz),

β2 (20.2– 24 Hz),

γ1 (24.2–34 Hz),

γ2 (34.2–44 Hz),

Spdl (10–16 Hz); Slow spindle (10–12 Hz); Fast spindle (12–16 Hz); standalone EEG

(2) Sleep quality, latency, time, efficiency

(3) ANOVA/sex, age, Tanner stage, relatedness

(1) No diff in absolute EEG pwr btw M & F in the lower freq bands (< 11 Hz) during NREM & REM sleep. F showed sign ↑ pwr in the σ band during NREM sleep & ↑ absolute pwr in higher freq (β1 to γ2) across NREM & REM sleep. When normalized, most pronounced sex diff were in NREM δ pwr. High-freq brain activity (16.2–44 Hz) was ↑ in F. F had sign ↑spdl amp & density. In analysis of F with no menarche & age-matched M, same results were observed for slow spdl; for fast spdl no sex diff in density

F showed > coherence than M across all freq bands in both NREM & REM, except in the α band where M had > values in occipital & temporal regions during NREM, & no sign sex diff during REM. The most pronounced sex diff were in δ during NREM & REM sleep, & in σ during NREM. Pwr decline occurred at a later age & pubertal maturation stage in M than F

(2) Sign age effects in EEG pwr in NREM & REM in δ band, w shift twd frontal regions as age ↑; α, σ, γ1, & γ2 bands (in NREM) shifted twd posterior regions w age. Older age linked to shorter slow spdl duration, ↓ spdl amp, & ↑ spdl freq. Age affected coherence across bands & states, with some connections ↓ but an overall ↑ in coherence with age

(3) Oscillatory activity across freq bands & sleep states more coherent in F than M, suggesting greater connectivity in F, except for α band. It is important taking sex into account when designing & interpreting studies of sleep neurophysiology

18. Mongrain V. et al. (2005); Sleep;

Canada; Quebec; Montreal; Sleep laboratory

(1) Explore relationship of chronotype on sleep stages & quantitative sleep EEG btw sexes

(2) Clinical trial

(3) Two-time assessment

(4) a. No shift work

    b. Healthy

    c. Non-smoker; > 85% sleep efficiency; latency < 30 min; AHI + PLMI < 5 per h; MSLT > 7 min; No drugs; no transmeridian travel 3 mos pre-study

    d. NR

(5) a. NR

    b. NR

    c. Bedtime btw 7–9 h; 3 + alc drink/2 + caff drink per d

    d. NR

(1) 24 (12 M/12F)

Morning: 12 (6 M/6F)

Evening: 12 (6 M/6F)

(2) NR

(3) 19–34 years;

Morning: (24.7 ± 1.5 years)

Evening: (23.4 ± 0.7 years)

(4) 50

(5) Language, occupation, social capital

(6) None

(7) Emerging & early adulthood

(1) δ (0.75–4 Hz),

θ (4–8 Hz),

α (8–12 Hz),

low σ (12–14 Hz),

high σ (14–16 Hz),

β (16–24 Hz); EEG via PSG

(2) Sleep quality, sleep regulation, sleep regulation

(3) 2-way ANOVA/sex

(1) F had ↑ spectral pwr in δ, θ & high σ compared to M

(2) Younger adult's regulation differs btw diff chronotypes

(3) Sleep-stage analysis showed no diff in sleep architecture btw morning & evening types. Morning-type M had > stage 1 sleep & ↓ sleep efficiency than evening-type M. Morning types had > spectral pwr in low σ during NREM sleep, while the biggest diff btw sexes was in high σ. The decay rate of SWA was faster in morning types but similar btw F & M

19. Mourtazaev et al. (1995);

Sleep;

Netherlands; Leiden; Participant’s homes

(1) Establish how age & sex affect NREM EEG; whether neuronal SW-generating mechanism is involved

(2) Cross-sectional

(3) One-time assessment (48-h recording; two 10-h periods starting “light off” analysed)

(4) a. NR

    b. Healthy; no somatic/neuro/psy d/o; no sleep-related meds

    c. No sleep complaints

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 59 (27 M/32F)

(2) NA

(3) 26–101 years

(4) 46

(5) NR

(6) Age

(7) Young (26–35), middle (51–60), late adulthood (66–75, 85–101)

(1) SW (0.5–2 Hz); EEG via PSG

(2) SW duration, SW%, max, total

(3) ANOVA/sex, age, & their interaction; Student–Newman–Keuls/age; mean, SD by sex & age group

(1) Total SWP was sign > in F than M

(2) There was a ↓ in all sleep parameters with ↑ age

(3) Sex has direct effect on EEG amp & does not affect internal generation of SW in EEG; may be caused by sex-related anatomical diff such as head size, thickness of skull, brain anatomic orientation, cell density & anatomy, electrochemical capacity of cells, etc

20. Pun M. et al. (2023);

J Sleep Res;

Canada; Alberta; Calgary; Participant’s home

(1) Examine relationship btw sleep spdl characteristics & cognitive function in older adults

(2) Cross-sectional

(3) One-time assessment

(4) a. NR

    e. BMI < 35 kg m⁻²; no cog decline (MoCA ≥ 24)

    f. Non-smoker for 1 + years; sedentary (< 30 min of exercise 4d/week)

    g. NR

(5) a. NR

    e. NR

    f. NR

    g. NR

(1) 21 (7 M/14F)

(2) NA

(3) 51–80 years

M (66.86 ± 8.6 years)

F (65.9 ± 5.0 years)

(4) 67

(5) Education

(6) None

(7) Middle & late adulthood

(1) Spdl density (11–16 Hz); EEG via PSG

(2) TST, sleep efficiency, latency, REM, time in each sleep stage, # of awakenings, sleep spdl characteristics, cognitive findings, # of spdls in NREM 2,3

(3) One-way ANOVA, Bonferroni-corrected pairwise comparisons/OSA, sex; mean, SD for no OSA by sex

(1) No sex difference in spdl density in frontal & central electrodes (calculated by SR authors using mean & SD data)

(2) Middle aged participants have ↓spdl density is associated w poor cognitive performance

(3) Fast spdls linked to better cog performance in F but weaker in M w/ OSA

21. Ringli M. et al. (2013); Int J Psychophysiol; Switzerland; Zurich; Zurich; Sleep laboratory

(1) To examine whether sexually dimorphic features are also reflected in topography of sleep SWA

(2) Cross-sectional

(3) Two-time assessment

(4) a. Right-handed

    b. No psychopathology, chronic medical diseases, sleep complaints/primary sleep d/o

    c. Non-smoker

    d. NR

(5) a. NR

    b. On psychoactive agent/meds

    c. > 4 cups of coffee/same amount of caff per d.; ≤ 1 glass of alc

    e. NR

(1) 22 (11 M/11F)

(2) NR

(3) M 8.7–19.4 years (13.4 ± 3.9 years)

F 9.1–19.0 years (13.4 ± 3.9 years)

(4) 50

(5) Tanner stage

(6) Age

(7) Childhood & adolescence

(1) SW (0.75–4.5 Hz); standalone EEG

(2) Sleep efficiency, latency

(3) ANOVA/sex, age

(1) F showed a sign ↑ in SWA pwr in the right & left temporal region compared to M. M had sign ↑ SWA in the right frontal region than F

(2) No sign effects of age

(3) In F, SWA during the first 60 min of NREM sleep was ↑ over bilateral cortical areas, while in M it was ↑ over the right prefrontal cortex. Sleep variables showed no sign sex diff except for a ↑ percentage of SWS & > absolute SWA in F

22. Rosinvil T. et al. (2021);

SleepJ;

Canada; Quebec; Montreal; Sleep laboratory

(1) Investigate a data-driven approach to identifying age & sex differences in SW

(2) Cohort study

(3) One-time assessment

(4) a. NR

    b. No drugs; no symptoms of depression/anxiety; AHI < 10; PLMI < 10

    c. NR

    d. Premenopausal women had regular cycle in last yr; menopausal women had no cycle for 1 + years & no vasomotor complaints

(5) a. Night worker

    b. On sleep-affecting meds

    c. Smoker; self-reported sleep complaints; unusual sleep duration (< 7 h/ > 9 h)

    d. Transmeridian travel 3 mos pre-study

    e. Perimenopausal F

(1) 284 (132 M/152F)

C1–younger: 97 (45 M/52F)

C1–older: 110 (49 M/61F)

C2–younger: 38 (19 M/19F)

C2–older: 39 (19 M/20F)

(2) NA

(3) 20–71

C1–younger (23.8 ± 2.8 years)

C1–older (57.5 ± 5.1 years)

C2–younger (22.7 ± 2.4 years)

C2–older (59.6 ± 5.4 years)

(4) Sex%M

(5) NR

(6) Age

(7) Emerging, early, middle, & late adulthood

(1) SW (PtP ≥ 75 μV & NegA ≥ 40 μV, negative to positive deflection ≥ 125 to ≤ 1,500 ≤ 1,000 ms); EEG via PSG

(2) Standard & adapted criteria, SNR

(3) Two-way ANOVA/sex, age; adaptation for amp detection/sex, age

(1) F had ↑ SW density, amp, steeper slopes w/ standard criteria. Age- & sex- adapted criteria removed sex diff in SW density, but F maintained ↑ amp & steeper slopes

(2) Older M showed the greatest decline in SW amp & slope compared to older F; older M produced higher proportion of low-amp SW (< 80 µV)

(3) ↑ SW amp in F may result from thinner skulls. Adapted criteria minimized detection bias, showing consistent age-related ↓ in SW gen., esp. in older M

23. Ujma P. P. et al. (2019);

Neurobiol Aging;

Hungary/Germany;

Central Hungary/ Bavaria; Budapest/

Munich; Sleep laboratory

(1) Investigate age & sex effects on sleep EEG functional connectivity in adults

(2) Quantitative study

(3) Two-time assessment

(4) a. NR

    b. No drugs except CC; no neuro/psy d/o

    c. < 2 cups of caff before noon

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

    e. Poor EEG data

(1) 172 (94 M/78F)

(2) NR

(3) 17–69 years (29.74 ± 10.71 years)

(4) 55

(5) NR

(6) Age

(7) Childhood & adolescence, emerging & early adulthood, middle & late adulthood

(1) δ (1–3 Hz),

θ (3.25–7.75 Hz),

α (8–10.75 Hz),

σ (11–15.75 Hz),

β (16–25 Hz)

γ (25.25–48 Hz)

frequencies; EEG via PSG

(2) Sleep efficiency

(3) Welch t-test/sex, age, general intelligence

(1) Connectivity was ↑ in F than in M in NREM σ freq range (13.5–14.5 Hz). M had ↑ connectivity in NREM & REM β ranges, (15.75–27.25 Hz) & (12.25–24.75 Hz), respectively, & in NREM high α /low σ (10.25–11.75 Hz), and in γ

(2) Connectivity in θ (NREM 4.25–5.5 Hz, REM 2.5–5.25 Hz) & β (NREM 30.75–40 Hz, REM 26.75–40 Hz) ranges ↑ w age. Connectivity ↓ in NREM σ range (10.25–14.75 Hz)

(3) F had sign > connectivity in the high σ freq range compared to M, w the opposite for the α / σ sigma & β ranges. Connectivity was not sign linked to general intelligence in either sex. Sleep spdl-freq activity loses synchrony w aging & found that high β pwr ↑ w age

24. Ujma P.P. et al. (2022);

Sci Rep; Germany/Hungary; Munich/Budapest; Sleep laboratory

(1) Study EEG envelope spectrum through comparing EEG of epileptic patient & healthy participants

(2) Retrospective study

(3) Multiple time assessment

(4) a. NR

    b. Healthy; no Hx of neuro/psy d/o; no drugs except CC

    c. > 2 cups of coffee before noon; no alc

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 176 (95 M/81F)

(2) NR

(3) 17–69 years (29.8 ± 10.66 years)

(4) 54

(5) NR

(6) Age

(7) Childhood & adolescence, emerging & early adulthood, middle & late adulthood

(1) Low δ (0.5–2 Hz),

high δ (2–4 Hz),

θ (4–7 Hz),

α (7–10 Hz)

low σ (10–12.5 Hz)

high σ (12.5–16 Hz),

β (16–30 Hz),

γ (30–49 Hz); standalone EEG

(2) Coupling btw different brain oscillations

(3) Elastic net regression using MATLAB lasso () function multivariate analyses/sex, age, IQ

(1) M ↓ amplitude of β pwr oscillation at < 0.75 Hz & > 1.75 Hz; M ↑ amplitude at ~ 1 Hz irrespective of sleep state

M ↓ amplitude of NREM low σ pwr oscillation at ~ 0.05–0.1 & ~ 0.5–1.5 Hz; M ↑ amplitude at ~ 0.25–0.5 Hz & > 1.75 Hz

(2) Older age linked to ↓low-freq & ↑ high-freq oscillations in NREM. In REM, age linked to a trend for ↑ low- & high-freq pwr oscillations & ↓ at ~ 0.5–1 Hz

(3) NREM envelope spectrum was a highly reliable individual marker strongly associated w ageing & partially sexually dimorphic

25. Ventura S. et al. (2022);

SleepJ;

Ireland; Cork; Sleep laboratory

(1) Investigate influences of sex on macrosleep structure & sleep spdls for infants of 4–5 mos

(2) Randomized control study

(3) One-time assessment

(4) a. NR

    b. Healthy

    c. NR

    d. Born after 37 wks of GA; singleton

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 91 (54 M/37F)

(2) NA

(3) 4–5 mos (39.8 weaks ± 1.2 weaks)

(4) 59

(5) Parent’s ethnicity, PNA, PMA

(6) Age (GA, PMA, PNA)

(7) Infancy & tolddlerhood

(1) Spdl (~ 11–15 Hz); standalone EEG

(2) Normative values for sleep macrostructure at 4–5 mos of age, brain symmetry index

(3) Univariable & multivariable linear regression analyses/sex, age (GA, PNA, PMA), timing of nap

(1) M had ↓ spdl pwr (25.4% & 24.5% less, in univariate & multivariate regression, respectively); no sex diff in spdl density

(2) Neither GA, PNA, nor PMA were statistically sign in models for spdl pwr, freq, & density

(3) Diff at young age may be driven by diff hormonal & brain connectivity profiles

26. Yoon J. et al. (2021);

J Sleep Res;

Korea; Gyeonggi; Ansan; Participant’s homes

(1) Identify role of age & sex in sleep structure w EEG spectral pwr analyses of middle-aged/older participants

(2) Cohort study

(3) Two-time assessment

(4) a. NR

    b. NR

    c. NR

    d. Underwent PSG protocol in the 6th biennial exam btw 2011–2012

(5) a. NR

    b. Major neuro/psy d/o

    c. Substance abuse

    d. Poor quality EEG

(1) 644 (330 M/314F)

(2) NR

(3) 45–69 years

M (57.7 ± 6.5yrs)

F (57.9 ± 6.9 years)

(4) 53

(5) Place of residence, ethnicity

(6) Age

(7) Middle & late adulthood

mourt

(1) δ (0.75–4 Hz),

θ (4–8 Hz),

α (8–12 Hz),

σ (12–14 Hz),

β (14–30 Hz); EEG via PSG

(2) Sleep efficiency

(3) Student’s t-test/sex; ANOVA/age; multivariable linear regression analyses of pwr /sex, age, AHI, BMI, TST

(1) Non-OSA M had ↑ β relative spectral pwr during the whole night, especially N1 sleep; M had ↑ σ relative pwr during N1. M had ↓ θ relative pwr during REM

M had ↓ absolute spectral pwr in all frequency bands during the whole night of sleep, REM, & NREM

(2) Relative δ pwr ↓, whereas θ, α & σ pwr ↑ during whole night w ageing. Effect of age & sex on relative spectral pwr varied throughout whole night, NREM & REM, & specific sleep stages

(3) Age & sex-related diff in sleep pwr were similar between OSA & non-OSA individuals

27. Yuksel D. et al. (2021);

Sleep Health;

USA; California; Menlo Park; Sleep laboratory

(1) Study sex & age diff in stress related sleep disturbances

(2) Multicenter study

(3) Two-time assessment

(4) a. NR

    b. Free of major mental & phy condition; no insomnia/other sleep d/o

    c. Keep sleep–wake cycle for 5d

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 106 (57 M/49F)

(2) NR

(3) 12.1–19.9

M (15 ± 1.9 years)

F (15.3 ± 2 years)

(4) 54

(5) Place of residence, ethnicity, pubertal development

(6) None

(7) Adolescence

(1) δ (0.3–4 Hz),

θ (> 4–8 Hz),

α (> 8–12 Hz)

σ (> 12–15 Hz),

low β (> 15–23 Hz),

high β (> 23–30 Hz); standalone EEG

(2) Macro/microstructure, sleep efficiency, WASO, NREM/REM, HR, ANS HR variability; night effect

(3) Mean, SD by sex

(1) No sign diff between sexes in relative power for all freq bands (calculated by SR authors using mean & SD data)

(2) NR

(3) Sex-based stress reactivity in sleep may contribute to ↑ insomnia rates in F

28. Zhang Y. Z. et al. (2021);

J Neurosci;

USA; California; Davis; Sleep laboratory

(1) Compile a dataset of longitudinal measurements of spdl microstructure in adolescence

(2) Longitudinal

(3) Multiple time assessment

(4) a. NR

    b. NR

    c. NR

    d. NR

(5) a. NR

    b. NR

    c. NR

    d. NR

(1) 98 (51 M/47F)

C6: 28 (17 M/11F)

C9: 32 (15 M/17F)

C12: 38 (19 M/19F)

(2) NR

(3) 5.96–18.4 years

(4) 52

C6: 61

C9: 47

C12: 50

(5) NR

(6) Age

(7) Early, middle & late childhood & adolescence

(1) Spdl (12–15 Hz); standalone EEG

(2) Central spdl change w age (freq, amp, density)

(3) Mixed-effects models/sex, age², age³

(1) For central spdl amp, M had sign larger ↓ & sign later age for most rapid ↓ (1.4 yrs later for M compared to F); for frontal spdl amp, the age of most rapid ↓ was sign later in M than F (1.5 yrs later in M). No sex diff in spdl density peak for central & frontal electrodes

(2) Spdl freq ↑ linearly with age; density peaked at 15 yrs; amp most rapid ↓ at 15

(3) Spdl amp ↓ is suggestive of synaptic pruning, which occurs earlier in F