Sleep EEG evidence of sex differences in adolescent brain maturation.

STUDY OBJECTIVES The steep decline in slow-wave (delta) electroencephalogram (EEG) intensity across adolescence is a prominent feature of late brain maturation. As a first step in determining whether the adolescent delta decline is similar in both sexes, we compared cross-sectional sleep EEG data from 9- and 12-year-old boys and girls. DESIGN All-night EEG recordings, 6 months apart, were conducted on each subject. SETTING EEG was recorded in the subjects' homes. PARTICIPANTS Thirty-two 9-year-olds and 38 12-year-olds are enrolled in a 4-year longitudinal study of adolescent sleep. There are equal numbers of each sex in both age cohorts. INTERVENTIONS N/A. MEASUREMENTS Using ambulatory recorders, EEG was recorded in the subjects' homes on their normal sleep schedule. For each of the 2 semi-annual recording periods, data from the 10 subjects from each age-sex group with the cleanest (fewest artifacts) signals were selected for crosssectional comparisons of visual scoring and EEG variables. All artifact-free 20-second non-rapid eye movement epochs were analyzed with power spectral and period-amplitude analysis. RESULTS In the 12-year-old cohort, delta power per minute was 37% higher in boys than girls. The 9-year-old cohort showed no sex difference. A second recording 6 months later produced similar results. CONCLUSION These cross-sectional data indicate that girls begin the steep adolescent decline in slow-wave EEG earlier than boys. We hypothesize that this reflects an earlier onset of adolescent synaptic pruning in females.