Developmental changes in the sleep electroencephalogram of adolescent boys and girls

Abstract

The sleep electroencephalogram (EEG) changes across adolescence; however, there are conflicting data as to whether EEG changes are regionally specific, are evident in non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, and whether there are sex differences. The present study seeks to resolve some of these issues in a combined cross-sectional and longitudinal analysis of sleep EEG in adolescents. Thirty-three healthy adolescents (18 boys, 15 girls; 11-14 years) were studied on two occasions 6-8 months apart. Cross-sectional analysis of data from the initial visit revealed significantly less slow-wave sleep, delta (0.3 to <4 Hz) and theta (4 to <8 Hz) power in both NREM and REM sleep with advancing age. The age-delta power relationship was significant at the occipital site, with age accounting for 26% of the variance. Longitudinal analysis revealed that NREM delta power declined significantly from the initial to follow-up visit, in association with declining delta amplitude and incidence (P < 0.01), with the effect being greatest at the occipital site. REM delta power also declined over time in association with reduced amplitude (P < 0.01). There were longitudinal reductions in theta, alpha and sigma power in NREM and REM sleep evident at the occipital site at follow-up (P < 0.01). No sex differences were apparent in the pattern of change with age for NREM or REM sleep. Declines in sleep EEG spectral power occur across adolescence in both boys and girls, particularly in the occipital derivation, and are not state-specific, occurring in both NREM and REM sleep.

Figure 1

Absolute delta power (log) at Frontal (F3-A2 or F4-A1), Central (C3-A2 or C4-A1), and Occipital (O1-A2 or O2-A1) sites during NREM sleep as a function of age in the cross-sectional analysis of adolescents at their initial visit. Data represent one point per subject. The solid line indicates a significant linear regression function fitted to the data for the occipital derivation.

Figure 2

Absolute electroencephalogram (EEG) power density in the frequency range of 0.3 – 23 Hz at Frontal (F3-A2 or F4-A2), Central (C3-A2 or C4-A1), and Occipital (O1-A2 or O2-A1) derivations during (A) NREM sleep and (B) REM sleep in adolescents at a 6-8 month follow-up visit expressed as a percentage of the initial visit. Solid bars along the x-axis denote significant time × derivation interaction effects. See text for details of statistical comparisons.

Figure 3

Results of quantitative analysis of the delta frequency band (0.3 – 4 Hz) of the EEG at Frontal (F3-A2 or F4-A1), Central (C3-A2 or C4-A1) and Occipital (O1-A2 or O2-A1) derivations during NREM sleep in adolescents at an initial visit and follow-up visit, 6-8 months later. Power density (Panel A) was calculated based on a fast Fourier transform of the EEG signal. Statistical comparisons were performed on log-transformed data but absolute values are presented in the Figure. Delta incidence (Panel B) and Amplitude (Panel C) were calculated from period amplitude analysis of the EEG signal. Values are shown as mean + SD. * p < 0.05, significantly different from initial visit. Delta power, incidence, and amplitude were highest at the frontal site.