NREM sleep as a novel protective cognitive reserve factor in the face of Alzheimer's disease pathology

Table 1 Demographics, PET, cognitive and sleep summary information (mean ± SD)

Variable	Aβ+ group (N = 31)	Aβ- group (N = 31)
Age (years)	75.97 ± 3.81	75.26 ± 6.08
Sex (% Female)	68	55
BMI	25.65 ± 3.91^a	24.74 ± 4.16
Education (years)	16.65 ± 2.06	17.19 ± 1.49
Global PiB DVR	1.34 ± 0.26	1.02 ± 0.03***
Time interval between PET and PSG sessions (years)	0.63 ± 0.06	0.62 ± 0.08
Total sleep time (min)	325 ± 72	330 ± 63
NREM2 time (min)	178 ± 57	192 ± 60
NREM3 time (min)	64 ± 53	52 ± 36
REM time (min)	48 ± 19	48 ± 21
WASO (min)	121 ± 64	121 ± 53
NREM SWA (relative delta power)	0.73 ± 0.07	0.68 ± 0.08*
MMSE	29.13 ± 1.06	28.90 ± 1.19
Item memory (d-prime)	0.56 ± 0.34^b	0.54 ± 0.41
Associative memory (d-prime)	0.51 ± 0.37^b	0.46 ± 0.38
Memory composite score (z-score)	-0.11 ± 0.78	-0.13 ± 0.93

In line with previous findings [27], NREM SWA, defined as NREM relative delta power in the 0.5 to 4 Hz frequency range, was significantly higher in the Aβ+ group compared to the Aβ- group (p = 0.01, see section ‘Association between Aβ burden and spectral power in the delta frequency range’ and Figure S1 in Additional file 1 [27, 31,32,33])
BMI Body Mass Index, PiB DVR Pittsburgh compound B Distribution Volume Ratio, PET Positron Emission Tomography, PSG Polysomnography, NREM Non-rapid eye movement, WASO Wake after sleep onset, SWA Slow wave activity, MMSE Mini-Mental State Examination
*p < 0.05
***p < 0.001
^aN = 30
^bN = 28

ISSN: 1741-7015