X. Tan et al., High internight reliability of computer-measured NREM delta, sigma, and beta: Biological implications, BIOL PSYCHI, 48(10), 2000, pp. 1010-1019
Background: Computer analysis of the sleep electroencephalogram (EEG) wavef
orms is widely employed, but there have been no systematic studies of its r
eliability.
Methods: The most commonly used computer methods are power spectral analysi
s with the fast-Fourier transform (FFT) and period amplitude analysis (PAA)
with zero cross or zero first derivative half-wave measurement. We applied
all three computer methods to the digitized EEG of 16 normal subjects who
underwent 5 consecutive nights of baseline (placebo) recording. We evaluate
d the internight reliability, of three non-rapid eye movement (NREM) freque
ncy bands of special importance to sleep research: delta (0.3-3 Hz), sigma
(12-15 Hz), and beta (15-23 Hz).
Results: Both FFT and the two methods of PAA gave excellent internight reli
ability for delta and sigma. Even a single night of recording correlated hi
ghly (r > .9) with the 5-night mean. Beta reliability was lower but still h
ighly significant for both the PAA and the FFT measures.
Conclusions: Computer-analyzed sleep EEG data are highly reliable. Period a
mplitude methods demonstrate that wave incidence and period as well as ampl
itude are reliable, indicating that the reliability of composite measures (
FFT power, PAA integrated amplitude) is not solely based on individual diff
erences in EEG amplitude. The high internight stability of NREM delta indic
ates that it possesses traitlike characteristics and is relatively independ
ent of day-to-day variations in state. (C) 2000 Society of Biological Psych
iatry.